和以前一樣，我不說dma基礎知識，你可以看看ldd3
這次我說的是三星平臺的dma，不是三星的某款芯片的dma使用。這主要得益於三星公司統一了接口。比如我後有的例子是在s3c2440上做的但是我是參考s3c64xx的spi驅動。
當然內核還是linux-3.2.36，我們看dma-ops.h
/* arch/arm/plat-samsung/include/plat/dma-ops.h
*
* Copyright (c) 2011 Samsung Electronics Co., Ltd.
* http://www.samsung.com
*
* Samsung DMA support
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef __SAMSUNG_DMA_OPS_H_
#define __SAMSUNG_DMA_OPS_H_ __FILE__
#include <linux/dmaengine.h>
struct samsung_dma_prep_info {
enum dma_transaction_type cap;//dma處理類型
enum dma_data_direction direction;//dma傳輸方向
dma_addr_t buf;//內存地址
unsigned long period;//
unsigned long len;//buf長度,sizeof(buf) * width，width在下面struct samsung_dma_info
/*
.c中調用
int len = (info->cap == DMA_CYCLIC) ? info->period : info->len;
...
我不是太清楚period和len區別
*/
void (*fp)(void *data);//dma中斷時會調用，一般作爲dma傳輸完成的接口
void *fp_param;//傳入上面fp的參數
};
struct samsung_dma_info {
enum dma_transaction_type cap;//dma處理類型
/*
if (info->cap == DMA_CYCLIC)
s3c2410_dma_setflags(dma_ch, S3C2410_DMAF_CIRCULAR);//chan->flags設置
這個可能和芯片有點關係
我的plat-s3c24xx中，通道請求函數
if (chan->flags & S3C2410_DMAF_AUTOSTART) {//如果設置爲自動運行，就調用start函數
s3c2410_dma_ctrl(chan->number | DMACH_LOW_LEVEL,
S3C2410_DMAOP_START);
}
沒有判斷S3C2410_DMAF_CIRCULAR標誌
*/
enum dma_data_direction direction;//dma傳輸方向
enum dma_slave_buswidth width;//要傳輸的數據寬度，就是（字節、半字、字）
dma_addr_t fifo;//外設地址
struct s3c2410_dma_client *client;
/*
struct s3c2410_dma_client {
char *name;
};
就是一個name,你申請通道時命名就可以了，主要dma中斷註冊是用、free通道時判斷
是不是正確通道
*/
};
struct samsung_dma_ops {
unsigned (*request)(enum dma_ch ch, struct samsung_dma_info *info);//請求會有些限制
//1.總是認爲我們的外圍設備是一個固定的地址
//2.總是認爲我們的內存地址增加
//3.硬件觸發
//4.所有傳輸完成產生中斷
//上面這個從數據手冊上看是可以設的，但是三星寫的驅動代碼沒有選的可能
int (*release)(unsigned ch, struct s3c2410_dma_client *client);//釋放
int (*prepare)(unsigned ch, struct samsung_dma_prep_info *info);//準備
//準備會把內存數據加入鏈表中，如果有數據在傳輸，會打開再加載開關
int (*trigger)(unsigned ch);//觸發
int (*started)(unsigned ch);//再次開始，實際就是再次載入數據
int (*flush)(unsigned ch);//清除通道數據
int (*stop)(unsigned ch);//停止
};
extern void *samsung_dmadev_get_ops(void);
extern void *s3c_dma_get_ops(void);
//去獲取一個struct samsung_dma_ops全局變量，
//然後調用驅動，這個倒是給我們提供了一種驅動之間調用的方法
static inline void *__samsung_dma_get_ops(void)
{
if (samsung_dma_is_dmadev())
return samsung_dmadev_get_ops();
else
return s3c_dma_get_ops();
}
/*
* samsung_dma_get_ops
* get the set of samsung dma operations
*/
//在驅動中調用這個
#define samsung_dma_get_ops() __samsung_dma_get_ops()
#endif /* __SAMSUNG_DMA_OPS_H_ */
如果你只是想看看應用接口，你可以在此打住，直接看《自娛自樂10》中dma使用的例子，增加你的理解。
如果你和我一樣死腦筋，你可以看看下面的源碼分析：主要有三個文件
下面這個文件，看的時候不要糾結，主要是爲第二個通道使用的，知道就行。
/* linux/arch/arm/plat-samsung/dma.c
*
* Copyright (c) 2003-2009 Simtec Electronics
* Ben Dooks <[email protected]>
* http://armlinux.simtec.co.uk/
*
* S3C DMA core
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
struct s3c2410_dma_buf;
/*
struct s3c2410_dma_buf {
struct s3c2410_dma_buf *next;
int magic; // magic
int size; // buffer size in bytes
dma_addr_t data; // start of DMA data
dma_addr_t ptr; // where the DMA got to [1]
void *id; // client's id
};
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <mach/dma.h>
#include <mach/irqs.h>
/* dma channel state information */
struct s3c2410_dma_chan s3c2410_chans[S3C_DMA_CHANNELS];
struct s3c2410_dma_chan *s3c_dma_chan_map[DMACH_MAX];
/* s3c_dma_lookup_channel
*
* change the dma channel number given into a real dma channel id
*/
//查找對應通道的struct s3c2410_dma_chan
//這個通道不是dma每個通道，是指外設對應的。
struct s3c2410_dma_chan *s3c_dma_lookup_channel(unsigned int channel)
{
if (channel & DMACH_LOW_LEVEL)
return &s3c2410_chans[channel & ~DMACH_LOW_LEVEL];
else
return s3c_dma_chan_map[channel];
}
/* do we need to protect the settings of the fields from
* irq?
*/
int s3c2410_dma_set_opfn(enum dma_ch channel, s3c2410_dma_opfn_t rtn)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
if (chan == NULL)
return -EINVAL;
pr_debug("%s: chan=%p, op rtn=%p\n", __func__, chan, rtn);
chan->op_fn = rtn;
//從下面可以看出在開始和結束時會調用這個函數
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_set_opfn);
int s3c2410_dma_set_buffdone_fn(enum dma_ch channel, s3c2410_dma_cbfn_t rtn)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
if (chan == NULL)
return -EINVAL;
pr_debug("%s: chan=%p, callback rtn=%p\n", __func__, chan, rtn);
//在s3c2410_dma_flush和中斷函數中調用
chan->callback_fn = rtn;
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_set_buffdone_fn);
//設置標誌
int s3c2410_dma_setflags(enum dma_ch channel, unsigned int flags)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
if (chan == NULL)
return -EINVAL;
chan->flags = flags;
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_setflags);下面是plat-s3c24xx中的，應該只適用s3c24xx芯片
文件有點大，我提供一個看的方法
1. 看init函數。
2. 看request函數。
3. 看s3c2410_dma_ctrl，裏面有停止、開始等。
4. 看中斷函數。
5. 看電源管理。
/* linux/arch/arm/plat-s3c24xx/dma.c
*
* Copyright 2003-2006 Simtec Electronics
* Ben Dooks <[email protected]>
*
* S3C2410 DMA core
*
* http://armlinux.simtec.co.uk/
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifdef CONFIG_S3C2410_DMA_DEBUG
#define DEBUG
#endif
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/syscore_ops.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/io.h>
#include <asm/system.h>
#include <asm/irq.h>
#include <mach/hardware.h>
#include <mach/dma.h>
#include <mach/map.h>
#include <plat/dma-s3c24xx.h>
#include <plat/regs-dma.h>
/* io map for dma */
static void __iomem *dma_base;
static struct kmem_cache *dma_kmem;
static int dma_channels;
static struct s3c24xx_dma_selection dma_sel;
//調試功能就不看了
/* debugging functions */
#define BUF_MAGIC (0xcafebabe)
#define dmawarn(fmt...) printk(KERN_DEBUG fmt)
#define dma_regaddr(chan, reg) ((chan)->regs + (reg))
#if 1
#define dma_wrreg(chan, reg, val) writel((val), (chan)->regs + (reg))
#else
static inline void
dma_wrreg(struct s3c2410_dma_chan *chan, int reg, unsigned long val)
{
pr_debug("writing %08x to register %08x\n",(unsigned int)val,reg);
writel(val, dma_regaddr(chan, reg));
}
#endif
#define dma_rdreg(chan, reg) readl((chan)->regs + (reg))
/* captured register state for debug */
struct s3c2410_dma_regstate {
unsigned long dcsrc; //源
unsigned long disrc; //目標
unsigned long dstat; //狀態
unsigned long dcon; //配置
unsigned long dmsktrig; //觸發屏蔽
};
//下面還是調試，不看了
#ifdef CONFIG_S3C2410_DMA_DEBUG
/* dmadbg_showregs
*
* simple debug routine to print the current state of the dma registers
*/
static void
dmadbg_capture(struct s3c2410_dma_chan *chan, struct s3c2410_dma_regstate *regs)
{
regs->dcsrc = dma_rdreg(chan, S3C2410_DMA_DCSRC);
regs->disrc = dma_rdreg(chan, S3C2410_DMA_DISRC);
regs->dstat = dma_rdreg(chan, S3C2410_DMA_DSTAT);
regs->dcon = dma_rdreg(chan, S3C2410_DMA_DCON);
regs->dmsktrig = dma_rdreg(chan, S3C2410_DMA_DMASKTRIG);
}
static void
dmadbg_dumpregs(const char *fname, int line, struct s3c2410_dma_chan *chan,
struct s3c2410_dma_regstate *regs)
{
printk(KERN_DEBUG "dma%d: %s:%d: DCSRC=%08lx, DISRC=%08lx, DSTAT=%08lx DMT=%02lx, DCON=%08lx\n",
chan->number, fname, line,
regs->dcsrc, regs->disrc, regs->dstat, regs->dmsktrig,
regs->dcon);
}
static void
dmadbg_showchan(const char *fname, int line, struct s3c2410_dma_chan *chan)
{
struct s3c2410_dma_regstate state;
dmadbg_capture(chan, &state);
printk(KERN_DEBUG "dma%d: %s:%d: ls=%d, cur=%p, %p %p\n",
chan->number, fname, line, chan->load_state,
chan->curr, chan->next, chan->end);
dmadbg_dumpregs(fname, line, chan, &state);
}
static void
dmadbg_showregs(const char *fname, int line, struct s3c2410_dma_chan *chan)
{
struct s3c2410_dma_regstate state;
dmadbg_capture(chan, &state);
dmadbg_dumpregs(fname, line, chan, &state);
}
#define dbg_showregs(chan) dmadbg_showregs(__func__, __LINE__, (chan))
#define dbg_showchan(chan) dmadbg_showchan(__func__, __LINE__, (chan))
#else
#define dbg_showregs(chan) do { } while(0)
#define dbg_showchan(chan) do { } while(0)
#endif /* CONFIG_S3C2410_DMA_DEBUG */
/* s3c2410_dma_stats_timeout
*
* Update DMA stats from timeout info
*/
//記錄dma傳輸用時
static void
s3c2410_dma_stats_timeout(struct s3c2410_dma_stats *stats, int val)
{
if (stats == NULL)
return;
if (val > stats->timeout_longest)
stats->timeout_longest = val;
if (val < stats->timeout_shortest)
stats->timeout_shortest = val;
stats->timeout_avg += val;
}
/* s3c2410_dma_waitforload
*
* wait for the DMA engine to load a buffer, and update the state accordingly
*/
//等待DMA引擎載入一個緩衝
static int
s3c2410_dma_waitforload(struct s3c2410_dma_chan *chan, int line)
{
int timeout = chan->load_timeout;//1 << 18
int took;
if (chan->load_state != S3C2410_DMALOAD_1LOADED) {
printk(KERN_ERR "dma%d: s3c2410_dma_waitforload() called in loadstate %d from line %d\n", chan->number, chan->load_state, line);
return 0;
}
if (chan->stats != NULL)
chan->stats->loads++;//載入加一
while (--timeout > 0) {
if ((dma_rdreg(chan, S3C2410_DMA_DSTAT) << (32-20)) != 0) {//左移11位，如果等於0，就表示DMA控制器就緒且傳輸計數值爲0
took = chan->load_timeout - timeout;//已計時間
s3c2410_dma_stats_timeout(chan->stats, took);//在上面
switch (chan->load_state) {
case S3C2410_DMALOAD_1LOADED:
chan->load_state = S3C2410_DMALOAD_1RUNNING;
break;
default:
printk(KERN_ERR "dma%d: unknown load_state in s3c2410_dma_waitforload() %d\n", chan->number, chan->load_state);
}
return 1;
}
}
if (chan->stats != NULL) {
chan->stats->timeout_failed++;//超時，錯誤加一
}
return 0;
}
/* s3c2410_dma_loadbuffer
*
* load a buffer, and update the channel state
*/
//載入
static inline int
s3c2410_dma_loadbuffer(struct s3c2410_dma_chan *chan,
struct s3c2410_dma_buf *buf)
{
unsigned long reload;
if (buf == NULL) {
dmawarn("buffer is NULL\n");
return -EINVAL;
}
pr_debug("s3c2410_chan_loadbuffer: loading buff %p (0x%08lx,0x%06x)\n",
buf, (unsigned long)buf->data, buf->size);
/* check the state of the channel before we do anything */
//狀態檢查，並警告
if (chan->load_state == S3C2410_DMALOAD_1LOADED) {//有一個載入
dmawarn("load_state is S3C2410_DMALOAD_1LOADED\n");
}
if (chan->load_state == S3C2410_DMALOAD_1LOADED_1RUNNING) {//一個載入一個運行
dmawarn("state is S3C2410_DMALOAD_1LOADED_1RUNNING\n");
}
/* it would seem sensible if we are the last buffer to not bother
* with the auto-reload bit, so that the DMA engine will not try
* and load another transfer after this one has finished...
*/
if (chan->load_state == S3C2410_DMALOAD_NONE) {
pr_debug("load_state is none, checking for noreload (next=%p)\n",
buf->next);
//next爲空說明是最後一個，就不需要再次載入
reload = (buf->next == NULL) ? S3C2410_DCON_NORELOAD : 0;
} else {
//pr_debug("load_state is %d => autoreload\n", chan->load_state);
reload = S3C2410_DCON_AUTORELOAD;
}
if ((buf->data & 0xf0000000) != 0x30000000) {//內存物理地址從0x30000000開始
dmawarn("dmaload: buffer is %p\n", (void *)buf->data);
}
writel(buf->data, chan->addr_reg);//數據寫入
dma_wrreg(chan, S3C2410_DMA_DCON,
chan->dcon | reload | (buf->size/chan->xfer_unit));//配置
chan->next = buf->next;
/* update the state of the channel */
switch (chan->load_state) {
case S3C2410_DMALOAD_NONE:
chan->load_state = S3C2410_DMALOAD_1LOADED;
break;
case S3C2410_DMALOAD_1RUNNING:
chan->load_state = S3C2410_DMALOAD_1LOADED_1RUNNING;
break;
default:
dmawarn("dmaload: unknown state %d in loadbuffer\n",
chan->load_state);
break;
}
return 0;
}
/* s3c2410_dma_call_op
*
* small routine to call the op routine with the given op if it has been
* registered
*/
static void
s3c2410_dma_call_op(struct s3c2410_dma_chan *chan, enum s3c2410_chan_op op)
{
//通過s3c2410_dma_set_opfn函數賦值
if (chan->op_fn != NULL) {
(chan->op_fn)(chan, op);
}
}
/* s3c2410_dma_buffdone
*
* small wrapper to check if callback routine needs to be called, and
* if so, call it
*/
static inline void
s3c2410_dma_buffdone(struct s3c2410_dma_chan *chan, struct s3c2410_dma_buf *buf,
enum s3c2410_dma_buffresult result)
{
#if 0
pr_debug("callback_fn=%p, buf=%p, id=%p, size=%d, result=%d\n",
chan->callback_fn, buf, buf->id, buf->size, result);
#endif
if (chan->callback_fn != NULL) {
(chan->callback_fn)(chan, buf->id, buf->size, result);
}
}
/* s3c2410_dma_start
*
* start a dma channel going
*/
static int s3c2410_dma_start(struct s3c2410_dma_chan *chan)
{
unsigned long tmp;
unsigned long flags;
pr_debug("s3c2410_start_dma: channel=%d\n", chan->number);
local_irq_save(flags);
if (chan->state == S3C2410_DMA_RUNNING) {
pr_debug("s3c2410_start_dma: already running (%d)\n", chan->state);
local_irq_restore(flags);
return 0;
}
//記錄狀態
chan->state = S3C2410_DMA_RUNNING;
/* check wether there is anything to load, and if not, see
* if we can find anything to load
*/
//判斷是否已載入載入
if (chan->load_state == S3C2410_DMALOAD_NONE) {
if (chan->next == NULL) {
printk(KERN_ERR "dma%d: channel has nothing loaded\n",
chan->number);
chan->state = S3C2410_DMA_IDLE;//沒有可載入的state記爲空閒
local_irq_restore(flags);
return -EINVAL;
}
s3c2410_dma_loadbuffer(chan, chan->next);//載入緩存
}
dbg_showchan(chan);//調試信息
/* enable the channel */
if (!chan->irq_enabled) {
enable_irq(chan->irq);//如果中斷關閉，開啓中斷
chan->irq_enabled = 1;
}
/* start the channel going */
tmp = dma_rdreg(chan, S3C2410_DMA_DMASKTRIG);
tmp &= ~S3C2410_DMASKTRIG_STOP;
tmp |= S3C2410_DMASKTRIG_ON;
dma_wrreg(chan, S3C2410_DMA_DMASKTRIG, tmp);//開始運行
pr_debug("dma%d: %08lx to DMASKTRIG\n", chan->number, tmp);
#if 0
/* the dma buffer loads should take care of clearing the AUTO
* reloading feature */
tmp = dma_rdreg(chan, S3C2410_DMA_DCON);
tmp &= ~S3C2410_DCON_NORELOAD;
dma_wrreg(chan, S3C2410_DMA_DCON, tmp);
#endif
s3c2410_dma_call_op(chan, S3C2410_DMAOP_START);//回調
dbg_showchan(chan);
/* if we've only loaded one buffer onto the channel, then chec
* to see if we have another, and if so, try and load it so when
* the first buffer is finished, the new one will be loaded onto
* the channel */
if (chan->next != NULL) {
if (chan->load_state == S3C2410_DMALOAD_1LOADED) {//已有一個正在載入
if (s3c2410_dma_waitforload(chan, __LINE__) == 0) {//等待...
pr_debug("%s: buff not yet loaded, no more todo\n",
__func__);
} else {
//這裏還有下面的，可以看出在s3c2410_dma_loadbuffer中
//S3C2410_DMALOAD_1RUNNING會使用AUTORELOAD模式
chan->load_state = S3C2410_DMALOAD_1RUNNING;
s3c2410_dma_loadbuffer(chan, chan->next);
}
} else if (chan->load_state == S3C2410_DMALOAD_1RUNNING) {
s3c2410_dma_loadbuffer(chan, chan->next);
}
}
local_irq_restore(flags);
return 0;
}
/* s3c2410_dma_canload
*
* work out if we can queue another buffer into the DMA engine
*/
static int
s3c2410_dma_canload(struct s3c2410_dma_chan *chan)
{
if (chan->load_state == S3C2410_DMALOAD_NONE ||
chan->load_state == S3C2410_DMALOAD_1RUNNING)
return 1;
return 0;
}
/* s3c2410_dma_enqueue
*
* queue an given buffer for dma transfer.
*
* id the device driver's id information for this buffer
* data the physical address of the buffer data
* size the size of the buffer in bytes
*
* If the channel is not running, then the flag S3C2410_DMAF_AUTOSTART
* is checked, and if set, the channel is started. If this flag isn't set,
* then an error will be returned.
*
* It is possible to queue more than one DMA buffer onto a channel at
* once, and the code will deal with the re-loading of the next buffer
* when necessary.
*/
//把數據加入鏈表
int s3c2410_dma_enqueue(unsigned int channel, void *id,
dma_addr_t data, int size)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
struct s3c2410_dma_buf *buf;
unsigned long flags;
if (chan == NULL)
return -EINVAL;
pr_debug("%s: id=%p, data=%08x, size=%d\n",
__func__, id, (unsigned int)data, size);
buf = kmem_cache_alloc(dma_kmem, GFP_ATOMIC);//申請內存
if (buf == NULL) {
pr_debug("%s: out of memory (%ld alloc)\n",
__func__, (long)sizeof(*buf));
return -ENOMEM;
}
//pr_debug("%s: new buffer %p\n", __func__, buf);
//dbg_showchan(chan);
//給buf賦值
buf->next = NULL;
buf->data = buf->ptr = data;
buf->size = size;
buf->id = id;
buf->magic = BUF_MAGIC;
local_irq_save(flags);
//chan->curr賦值並把buf加入鏈表中
if (chan->curr == NULL) {
/* we've got nothing loaded... */
pr_debug("%s: buffer %p queued onto empty channel\n",
__func__, buf);
chan->curr = buf;
chan->end = buf;
chan->next = NULL;
} else {
pr_debug("dma%d: %s: buffer %p queued onto non-empty channel\n",
chan->number, __func__, buf);
if (chan->end == NULL)
pr_debug("dma%d: %s: %p not empty, and chan->end==NULL?\n",
chan->number, __func__, chan);
chan->end->next = buf;
chan->end = buf;
}
/* if necessary, update the next buffer field */
if (chan->next == NULL)
chan->next = buf;
/* check to see if we can load a buffer */
if (chan->state == S3C2410_DMA_RUNNING) {
if (chan->load_state == S3C2410_DMALOAD_1LOADED && 1) {//當前是否有一個在傳輸
if (s3c2410_dma_waitforload(chan, __LINE__) == 0) {//等待
printk(KERN_ERR "dma%d: loadbuffer:"
"timeout loading buffer\n",
chan->number);
dbg_showchan(chan);
local_irq_restore(flags);
return -EINVAL;
}
}
while (s3c2410_dma_canload(chan) && chan->next != NULL) {//可加載且chan->next不爲空
s3c2410_dma_loadbuffer(chan, chan->next);
}
} else if (chan->state == S3C2410_DMA_IDLE) {
if (chan->flags & S3C2410_DMAF_AUTOSTART) {//如果設置爲自動運行，就調用start函數
s3c2410_dma_ctrl(chan->number | DMACH_LOW_LEVEL,
S3C2410_DMAOP_START);
}
}
local_irq_restore(flags);
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_enqueue);
static inline void
s3c2410_dma_freebuf(struct s3c2410_dma_buf *buf)
{
int magicok = (buf->magic == BUF_MAGIC);
buf->magic = -1;
if (magicok) {
kmem_cache_free(dma_kmem, buf);
} else {
printk("s3c2410_dma_freebuf: buff %p with bad magic\n", buf);
}
}
/* s3c2410_dma_lastxfer
*
* called when the system is out of buffers, to ensure that the channel
* is prepared for shutdown.
*/
static inline void
s3c2410_dma_lastxfer(struct s3c2410_dma_chan *chan)
{
#if 0
pr_debug("dma%d: s3c2410_dma_lastxfer: load_state %d\n",
chan->number, chan->load_state);
#endif
switch (chan->load_state) {
case S3C2410_DMALOAD_NONE:
break;
case S3C2410_DMALOAD_1LOADED:
if (s3c2410_dma_waitforload(chan, __LINE__) == 0) {
/* flag error? */
printk(KERN_ERR "dma%d: timeout waiting for load (%s)\n",
chan->number, __func__);
return;
}
break;
case S3C2410_DMALOAD_1LOADED_1RUNNING:
/* I believe in this case we do not have anything to do
* until the next buffer comes along, and we turn off the
* reload */
return;
default:
pr_debug("dma%d: lastxfer: unhandled load_state %d with no next\n",
chan->number, chan->load_state);
return;
}
/* hopefully this'll shut the damned thing up after the transfer... */
dma_wrreg(chan, S3C2410_DMA_DCON, chan->dcon | S3C2410_DCON_NORELOAD);
}
#define dmadbg2(x...)
static irqreturn_t
s3c2410_dma_irq(int irq, void *devpw)
{
struct s3c2410_dma_chan *chan = (struct s3c2410_dma_chan *)devpw;
struct s3c2410_dma_buf *buf;
buf = chan->curr;
dbg_showchan(chan);
/* modify the channel state */
//更新狀態
switch (chan->load_state) {
case S3C2410_DMALOAD_1RUNNING:
/* TODO - if we are running only one buffer, we probably
* want to reload here, and then worry about the buffer
* callback */
chan->load_state = S3C2410_DMALOAD_NONE;
break;
case S3C2410_DMALOAD_1LOADED:
/* iirc, we should go back to NONE loaded here, we
* had a buffer, and it was never verified as being
* loaded.
*/
chan->load_state = S3C2410_DMALOAD_NONE;
break;
case S3C2410_DMALOAD_1LOADED_1RUNNING:
/* we'll worry about checking to see if another buffer is
* ready after we've called back the owner. This should
* ensure we do not wait around too long for the DMA
* engine to start the next transfer
*/
chan->load_state = S3C2410_DMALOAD_1LOADED;
break;
case S3C2410_DMALOAD_NONE:
printk(KERN_ERR "dma%d: IRQ with no loaded buffer?\n",
chan->number);
break;
default:
printk(KERN_ERR "dma%d: IRQ in invalid load_state %d\n",
chan->number, chan->load_state);
break;
}
if (buf != NULL) {
/* update the chain to make sure that if we load any more
* buffers when we call the callback function, things should
* work properly */
//更新鏈表
chan->curr = buf->next;
buf->next = NULL;
if (buf->magic != BUF_MAGIC) {
printk(KERN_ERR "dma%d: %s: buf %p incorrect magic\n",
chan->number, __func__, buf);
return IRQ_HANDLED;
}
s3c2410_dma_buffdone(chan, buf, S3C2410_RES_OK);//回調，使一些事情工作正常
/* free resouces */
s3c2410_dma_freebuf(buf);//釋放空間
} else {
}
/* only reload if the channel is still running... our buffer done
* routine may have altered the state by requesting the dma channel
* to stop or shutdown... */
/* todo: check that when the channel is shut-down from inside this
* function, we cope with unsetting reload, etc */
if (chan->next != NULL && chan->state != S3C2410_DMA_IDLE) {
unsigned long flags;
switch (chan->load_state) {
case S3C2410_DMALOAD_1RUNNING:
/* don't need to do anything for this state */
break;
case S3C2410_DMALOAD_NONE:
/* can load buffer immediately */
break;
case S3C2410_DMALOAD_1LOADED:
if (s3c2410_dma_waitforload(chan, __LINE__) == 0) {//等待傳輸完
/* flag error? */
printk(KERN_ERR "dma%d: timeout waiting for load (%s)\n",
chan->number, __func__);
return IRQ_HANDLED;
}
break;
case S3C2410_DMALOAD_1LOADED_1RUNNING:
goto no_load;
default:
printk(KERN_ERR "dma%d: unknown load_state in irq, %d\n",
chan->number, chan->load_state);
return IRQ_HANDLED;
}
local_irq_save(flags);
s3c2410_dma_loadbuffer(chan, chan->next);//再次載入
local_irq_restore(flags);
} else {
s3c2410_dma_lastxfer(chan);//最後一個緩衝區
/* see if we can stop this channel.. */
if (chan->load_state == S3C2410_DMALOAD_NONE) {
pr_debug("dma%d: end of transfer, stopping channel (%ld)\n",
chan->number, jiffies);
s3c2410_dma_ctrl(chan->number | DMACH_LOW_LEVEL,
S3C2410_DMAOP_STOP);//停止
}
}
no_load:
return IRQ_HANDLED;
}
static struct s3c2410_dma_chan *s3c2410_dma_map_channel(int channel);
/* s3c2410_request_dma
*
* get control of an dma channel
*/
//獲取一個dma通道
//下面你會看到，獲取一個通道信息並註冊中斷
int s3c2410_dma_request(enum dma_ch channel,
struct s3c2410_dma_client *client,
void *dev)
{
struct s3c2410_dma_chan *chan;
unsigned long flags;
int err;
pr_debug("dma%d: s3c2410_request_dma: client=%s, dev=%p\n",
channel, client->name, dev);
local_irq_save(flags);
//請求一個通道，下面有詳細說明
chan = s3c2410_dma_map_channel(channel);
if (chan == NULL) {
local_irq_restore(flags);
return -EBUSY;
}
dbg_showchan(chan);
chan->client = client;
chan->in_use = 1;//標誌爲使用
if (!chan->irq_claimed) {
pr_debug("dma%d: %s : requesting irq %d\n",
channel, __func__, chan->irq);
chan->irq_claimed = 1;//中斷聲明標誌爲1
local_irq_restore(flags);
err = request_irq(chan->irq, s3c2410_dma_irq, IRQF_DISABLED,
client->name, (void *)chan);
local_irq_save(flags);
if (err) {
chan->in_use = 0;
chan->irq_claimed = 0;
local_irq_restore(flags);
printk(KERN_ERR "%s: cannot get IRQ %d for DMA %d\n",
client->name, chan->irq, chan->number);
return err;
}
chan->irq_enabled = 1;
}
local_irq_restore(flags);
/* need to setup */
pr_debug("%s: channel initialised, %p\n", __func__, chan);
return chan->number | DMACH_LOW_LEVEL;
}
EXPORT_SYMBOL(s3c2410_dma_request);
/* s3c2410_dma_free
*
* release the given channel back to the system, will stop and flush
* any outstanding transfers, and ensure the channel is ready for the
* next claimant.
*
* Note, although a warning is currently printed if the freeing client
* info is not the same as the registrant's client info, the free is still
* allowed to go through.
*/
int s3c2410_dma_free(enum dma_ch channel, struct s3c2410_dma_client *client)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
unsigned long flags;
if (chan == NULL)
return -EINVAL;
local_irq_save(flags);
if (chan->client != client) {//檢查是否爲正確通道
printk(KERN_WARNING "dma%d: possible free from different client (channel %p, passed %p)\n",
channel, chan->client, client);
}
/* sort out stopping and freeing the channel */
if (chan->state != S3C2410_DMA_IDLE) {
pr_debug("%s: need to stop dma channel %p\n",
__func__, chan);
/* possibly flush the channel */
s3c2410_dma_ctrl(channel, S3C2410_DMAOP_STOP);//不是空閒，就停止通道
}
chan->client = NULL;
chan->in_use = 0;
if (chan->irq_claimed)
free_irq(chan->irq, (void *)chan);//如果註冊的中斷就釋放
chan->irq_claimed = 0;
if (!(channel & DMACH_LOW_LEVEL))
s3c_dma_chan_map[channel] = NULL;//對應的數據置空
local_irq_restore(flags);
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_free);
static int s3c2410_dma_dostop(struct s3c2410_dma_chan *chan)
{
unsigned long flags;
unsigned long tmp;
pr_debug("%s:\n", __func__);
dbg_showchan(chan);//調試不看了
local_irq_save(flags);
s3c2410_dma_call_op(chan, S3C2410_DMAOP_STOP);
//(chan->op_fn)(chan, op); 回調函數
tmp = dma_rdreg(chan, S3C2410_DMA_DMASKTRIG);//讀對應通道的寄存器
tmp |= S3C2410_DMASKTRIG_STOP;//DMASKTRIG的第2位是STOP
//tmp &= ~S3C2410_DMASKTRIG_ON;
dma_wrreg(chan, S3C2410_DMA_DMASKTRIG, tmp);
#if 0 //爲了適合WinCE，關閉再加載
/* should also clear interrupts, according to WinCE BSP */
tmp = dma_rdreg(chan, S3C2410_DMA_DCON);
tmp |= S3C2410_DCON_NORELOAD;
dma_wrreg(chan, S3C2410_DMA_DCON, tmp);
#endif
/* should stop do this, or should we wait for flush? */
chan->state = S3C2410_DMA_IDLE;//dma狀態
chan->load_state = S3C2410_DMALOAD_NONE;//dma數據傳輸狀態
local_irq_restore(flags);
return 0;
}
static void s3c2410_dma_waitforstop(struct s3c2410_dma_chan *chan)
{
unsigned long tmp;
unsigned int timeout = 0x10000;
while (timeout-- > 0) {
tmp = dma_rdreg(chan, S3C2410_DMA_DMASKTRIG);
if (!(tmp & S3C2410_DMASKTRIG_ON))//判斷DMASKTRIG寄存器第1位是否爲0
return;
}
pr_debug("dma%d: failed to stop?\n", chan->number);
}
/* s3c2410_dma_flush
*
* stop the channel, and remove all current and pending transfers
*/
//停止通道，並移除當前和即將發生的傳輸
static int s3c2410_dma_flush(struct s3c2410_dma_chan *chan)
{
struct s3c2410_dma_buf *buf, *next;
unsigned long flags;
pr_debug("%s: chan %p (%d)\n", __func__, chan, chan->number);
dbg_showchan(chan);
local_irq_save(flags);
if (chan->state != S3C2410_DMA_IDLE) {
pr_debug("%s: stopping channel...\n", __func__ );
//不是空閒，調用s3c2410_dma_dostop
s3c2410_dma_ctrl(chan->number, S3C2410_DMAOP_STOP);
}
buf = chan->curr;
if (buf == NULL)
buf = chan->next;
//清除數據
chan->curr = chan->next = chan->end = NULL;
//釋放空間
if (buf != NULL) {
for ( ; buf != NULL; buf = next) {
next = buf->next;
pr_debug("%s: free buffer %p, next %p\n",
__func__, buf, buf->next);
s3c2410_dma_buffdone(chan, buf, S3C2410_RES_ABORT);//回調函數調用
s3c2410_dma_freebuf(buf);//就是調用kmem_cache_free釋放
}
}
dbg_showregs(chan);
s3c2410_dma_waitforstop(chan);//等待停止
#if 0
/* should also clear interrupts, according to WinCE BSP */
{
unsigned long tmp;
tmp = dma_rdreg(chan, S3C2410_DMA_DCON);
tmp |= S3C2410_DCON_NORELOAD;
dma_wrreg(chan, S3C2410_DMA_DCON, tmp);
}
#endif
dbg_showregs(chan);
local_irq_restore(flags);
return 0;
}
static int s3c2410_dma_started(struct s3c2410_dma_chan *chan)
{
unsigned long flags;
local_irq_save(flags);
dbg_showchan(chan);
/* if we've only loaded one buffer onto the channel, then chec
* to see if we have another, and if so, try and load it so when
* the first buffer is finished, the new one will be loaded onto
* the channel */
//下面的判斷可以查看s3c2410_dma_start()
if (chan->next != NULL) {
if (chan->load_state == S3C2410_DMALOAD_1LOADED) {
if (s3c2410_dma_waitforload(chan, __LINE__) == 0) {
pr_debug("%s: buff not yet loaded, no more todo\n",
__func__);
} else {
chan->load_state = S3C2410_DMALOAD_1RUNNING;
s3c2410_dma_loadbuffer(chan, chan->next);
}
} else if (chan->load_state == S3C2410_DMALOAD_1RUNNING) {
s3c2410_dma_loadbuffer(chan, chan->next);
}
}
local_irq_restore(flags);
return 0;
}
//dma 控制函數
int
s3c2410_dma_ctrl(enum dma_ch channel, enum s3c2410_chan_op op)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
if (chan == NULL)
return -EINVAL;
switch (op) {
case S3C2410_DMAOP_START://開始
return s3c2410_dma_start(chan);
case S3C2410_DMAOP_STOP://停止
return s3c2410_dma_dostop(chan);
case S3C2410_DMAOP_PAUSE://暫停
case S3C2410_DMAOP_RESUME:
return -ENOENT;
case S3C2410_DMAOP_FLUSH://沖掉
return s3c2410_dma_flush(chan);
case S3C2410_DMAOP_STARTED://再次開始
return s3c2410_dma_started(chan);
case S3C2410_DMAOP_TIMEOUT://超時
return 0;
}
return -ENOENT; /* unknown, don't bother */
}
EXPORT_SYMBOL(s3c2410_dma_ctrl);
/* DMA configuration for each channel
*
* DISRCC -> source of the DMA (AHB,APB)
* DISRC -> source address of the DMA
* DIDSTC -> destination of the DMA (AHB,APD)
* DIDST -> destination address of the DMA
*/
/* s3c2410_dma_config
*
* xfersize: size of unit in bytes (1,2,4)
*/
int s3c2410_dma_config(enum dma_ch channel,
int xferunit)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
unsigned int dcon;
pr_debug("%s: chan=%d, xfer_unit=%d\n", __func__, channel, xferunit);
if (chan == NULL)
return -EINVAL;
dcon = chan->dcon & dma_sel.dcon_mask;
pr_debug("%s: dcon is %08x\n", __func__, dcon);
//DCON寄存器的24~26位選擇請求源
switch (chan->req_ch) {
case DMACH_I2S_IN:
case DMACH_I2S_OUT:
case DMACH_PCM_IN:
case DMACH_PCM_OUT:
case DMACH_MIC_IN:
default:
dcon |= S3C2410_DCON_HANDSHAKE;
dcon |= S3C2410_DCON_SYNC_PCLK;
break;
case DMACH_SDI:
/* note, ensure if need HANDSHAKE or not */
dcon |= S3C2410_DCON_SYNC_PCLK;
break;
case DMACH_XD0:
case DMACH_XD1:
dcon |= S3C2410_DCON_HANDSHAKE;
dcon |= S3C2410_DCON_SYNC_HCLK;
break;
}
//上面的HANDSHAKE是選擇握手模式
//除了SDI要選，其他的都是握手模式，chan->dcon來記錄你的dcon的配置
//傳輸大小
switch (xferunit) {
case 1:
dcon |= S3C2410_DCON_BYTE;
break;
case 2:
dcon |= S3C2410_DCON_HALFWORD;
break;
case 4:
dcon |= S3C2410_DCON_WORD;
break;
default:
pr_debug("%s: bad transfer size %d\n", __func__, xferunit);
return -EINVAL;
}
dcon |= S3C2410_DCON_HWTRIG;//硬件觸發
dcon |= S3C2410_DCON_INTREQ;//所有傳輸完成產生中斷
pr_debug("%s: dcon now %08x\n", __func__, dcon);
//記錄下配置
chan->dcon = dcon;
chan->xfer_unit = xferunit;
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_config);
/* s3c2410_dma_devconfig
*
* configure the dma source/destination hardware type and address
*
* source: DMA_FROM_DEVICE: source is hardware
* DMA_TO_DEVICE: source is memory
*
* devaddr: physical address of the source
*/
int s3c2410_dma_devconfig(enum dma_ch channel,
enum dma_data_direction source,
unsigned long devaddr)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
unsigned int hwcfg;
if (chan == NULL)
return -EINVAL;
pr_debug("%s: source=%d, devaddr=%08lx\n",
__func__, (int)source, devaddr);
chan->source = source;//源類型，內存或者硬件
chan->dev_addr = devaddr;//
switch (chan->req_ch) {
case DMACH_XD0:
case DMACH_XD1:
hwcfg = 0; /* AHB */
break;
default:
hwcfg = S3C2410_DISRCC_APB;
}
//除了XD0和XD1在AHB總線上，其他都是APB
/* always assume our peripheral desintation is a fixed
* address in memory. */
//總是認爲我們的外圍設備是一個固定的地址
hwcfg |= S3C2410_DISRCC_INC;//在傳輸後地址不改變
switch (source) {
case DMA_FROM_DEVICE://源是硬件
/* source is hardware */
pr_debug("%s: hw source, devaddr=%08lx, hwcfg=%d\n",
__func__, devaddr, hwcfg);
dma_wrreg(chan, S3C2410_DMA_DISRCC, hwcfg & 3);//源控制
dma_wrreg(chan, S3C2410_DMA_DISRC, devaddr);//源地址
dma_wrreg(chan, S3C2410_DMA_DIDSTC, (0<<1) | (0<<0));//目標控制：系統總線，地址增加
chan->addr_reg = dma_regaddr(chan, S3C2410_DMA_DIDST);//記下內存地址
break;
case DMA_TO_DEVICE://源是內存
/* source is memory */
pr_debug("%s: mem source, devaddr=%08lx, hwcfg=%d\n",
__func__, devaddr, hwcfg);
dma_wrreg(chan, S3C2410_DMA_DISRCC, (0<<1) | (0<<0));//源：系統總線，地址增加
dma_wrreg(chan, S3C2410_DMA_DIDST, devaddr);//目標地址地址
dma_wrreg(chan, S3C2410_DMA_DIDSTC, hwcfg & 3);//目標控制
chan->addr_reg = dma_regaddr(chan, S3C2410_DMA_DISRC);//記下內存地址
break;
default:
printk(KERN_ERR "dma%d: invalid source type (%d)\n",
channel, source);
return -EINVAL;
}
if (dma_sel.direction != NULL)//s3c2440爲空
(dma_sel.direction)(chan, chan->map, source);
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_devconfig);
/* s3c2410_dma_getposition
*
* returns the current transfer points for the dma source and destination
*/
//當前源或目標地址
int s3c2410_dma_getposition(enum dma_ch channel, dma_addr_t *src, dma_addr_t *dst)
{
struct s3c2410_dma_chan *chan = s3c_dma_lookup_channel(channel);
if (chan == NULL)
return -EINVAL;
if (src != NULL)
*src = dma_rdreg(chan, S3C2410_DMA_DCSRC);
if (dst != NULL)
*dst = dma_rdreg(chan, S3C2410_DMA_DCDST);
return 0;
}
EXPORT_SYMBOL(s3c2410_dma_getposition);
/* system core operations */
#ifdef CONFIG_PM
static void s3c2410_dma_suspend_chan(struct s3c2410_dma_chan *cp)
{
printk(KERN_DEBUG "suspending dma channel %d\n", cp->number);
if (dma_rdreg(cp, S3C2410_DMA_DMASKTRIG) & S3C2410_DMASKTRIG_ON) {
/* the dma channel is still working, which is probably
* a bad thing to do over suspend/resume. We stop the
* channel and assume that the client is either going to
* retry after resume, or that it is broken.
*/
printk(KERN_INFO "dma: stopping channel %d due to suspend\n",
cp->number);
s3c2410_dma_dostop(cp);
}
}
static int s3c2410_dma_suspend(void)
{
struct s3c2410_dma_chan *cp = s3c2410_chans;
int channel;
for (channel = 0; channel < dma_channels; cp++, channel++)
s3c2410_dma_suspend_chan(cp);
return 0;
}
static void s3c2410_dma_resume_chan(struct s3c2410_dma_chan *cp)
{
unsigned int no = cp->number | DMACH_LOW_LEVEL;
/* restore channel's hardware configuration */
if (!cp->in_use)
return;
printk(KERN_INFO "dma%d: restoring configuration\n", cp->number);
s3c2410_dma_config(no, cp->xfer_unit);
s3c2410_dma_devconfig(no, cp->source, cp->dev_addr);
/* re-select the dma source for this channel */
if (cp->map != NULL)
dma_sel.select(cp, cp->map);
}
static void s3c2410_dma_resume(void)
{
struct s3c2410_dma_chan *cp = s3c2410_chans + dma_channels - 1;
int channel;
for (channel = dma_channels - 1; channel >= 0; cp++, channel--)
s3c2410_dma_resume_chan(cp);
}
#else
#define s3c2410_dma_suspend NULL
#define s3c2410_dma_resume NULL
#endif /* CONFIG_PM */
/*
struct syscore_ops {
struct list_head node;
int (*suspend)(void);
void (*resume)(void);
void (*shutdown)(void);
};
這個syscore是通過一個全局的list管理的,如下
LIST_HEAD(syscore_ops_list);
*/
struct syscore_ops dma_syscore_ops = {
.suspend = s3c2410_dma_suspend,
.resume = s3c2410_dma_resume,
};
/* kmem cache implementation */
//下面看到
static void s3c2410_dma_cache_ctor(void *p)
{
memset(p, 0, sizeof(struct s3c2410_dma_buf));
}
/* initialisation code */
static int __init s3c24xx_dma_syscore_init(void)
{
//註冊的實質就是
//list_add_tail(&ops->node, &syscore_ops_list);
//加入鏈表
register_syscore_ops(&dma_syscore_ops);
return 0;
}
//late_initcall啓動時會執行，在那個階段我們就不管了
late_initcall(s3c24xx_dma_syscore_init);
/*
下面這個函數告訴我們這些__init函數的調用位置
static int __init s3c2440_dma_add(struct sys_device *sysdev)
{
s3c2410_dma_init();
s3c24xx_dma_order_set(&s3c2440_dma_order);
return s3c24xx_dma_init_map(&s3c2440_dma_sel);
}
static struct sysdev_driver s3c2440_dma_driver = {
.add = s3c2440_dma_add,
};
static int __init s3c2440_dma_init(void)
{
return sysdev_driver_register(&s3c2440_sysclass, &s3c2440_dma_driver);
}
struct sysdev_class s3c2440_sysclass = {
.name = "s3c2440-core",
};
static struct sys_device s3c2440_sysdev = {
.cls = &s3c2440_sysclass,
};
在s3c2440_init()中會調用
sysdev_register(&s3c2440_sysdev);
我們從這可以看到設備與驅動的概念，當然這不是我們的重點，我只說想說
s3c2440_dma_add初始化會被調用，我們就安初始化調用過程來看代碼
啓動時調用
arch_initcall(s3c2440_dma_init);
*/
//s3c24xx_dma_init在下面s3c2410_dma_init()被調用
//s3c2440或s3c2410平臺s3c24xx_dma_init(4, IRQ_DMA0, 0x40);
//4個通道，中斷號爲IRQ_DMA0，0x40 * 4就是io要映射的大小
int __init s3c24xx_dma_init(unsigned int channels, unsigned int irq,
unsigned int stride)
{
struct s3c2410_dma_chan *cp;
int channel;
int ret;
printk("S3C24XX DMA Driver, Copyright 2003-2006 Simtec Electronics\n");
dma_channels = channels;
//寄存器映射
dma_base = ioremap(S3C24XX_PA_DMA, stride * channels);
if (dma_base == NULL) {
printk(KERN_ERR "dma failed to remap register block\n");
return -ENOMEM;
}
//申請後備緩存
dma_kmem = kmem_cache_create("dma_desc",
sizeof(struct s3c2410_dma_buf), 0,
SLAB_HWCACHE_ALIGN,
s3c2410_dma_cache_ctor);
/*
原型：
struct kmem_cache *kmem_cache_create(const char *name, size_t size,
size_t align, unsigned long flags, void (*ctor)(void *))
SLAB_HWCACHE_ALIGN:
這個標誌需要每個數據對象被對齊到一個緩存行; 實際對齊依賴主機平
臺的緩存分佈. 這個選項可以是一個好的選擇, 如果在 SMP 機器上你的
緩存包含頻繁存取的項. 但是, 用來獲得緩存行對齊的填充可以浪費可
觀的內存量.
s3c2410_dma_cache_ctor：
構造函數，上面可以看到就是把申請的內存空間清零。
*/
if (dma_kmem == NULL) {
printk(KERN_ERR "dma failed to make kmem cache\n");
ret = -ENOMEM;
goto err;
}
/*
在mach-s3c2410/include/mach/dma.h下定義的結構體
struct s3c2410_dma_chan s3c2410_chans[S3C_DMA_CHANNELS];
*/
for (channel = 0; channel < channels; channel++) {
cp = &s3c2410_chans[channel];
memset(cp, 0, sizeof(struct s3c2410_dma_chan));
/* dma channel irqs are in order.. */
cp->number = channel; //通道號
cp->irq = channel + irq; //中斷號
cp->regs = dma_base + (channel * stride); //寄存器基地址
/* point current stats somewhere */
/*
struct s3c2410_dma_stats *stats;
struct s3c2410_dma_stats stats_store;
下面就是個指針初始化
*/
cp->stats = &cp->stats_store;
cp->stats_store.timeout_shortest = LONG_MAX;//#define LONG_MAX ((long)(~0UL>>1))
/* basic channel configuration */
cp->load_timeout = 1<<18;//向dma載入緩衝的超時時間
printk("DMA channel %d at %p, irq %d\n",
cp->number, cp->regs, cp->irq);
}
return 0;
err:
kmem_cache_destroy(dma_kmem);
iounmap(dma_base);
dma_base = NULL;
return ret;
}
int __init s3c2410_dma_init(void)
{
return s3c24xx_dma_init(4, IRQ_DMA0, 0x40);
}
static inline int is_channel_valid(unsigned int channel)
{
//#define DMA_CH_VALID (1<<31)
return (channel & DMA_CH_VALID);
}
static struct s3c24xx_dma_order *dma_order;
/* s3c2410_dma_map_channel()
*
* turn the virtual channel number into a real, and un-used hardware
* channel.
*
* first, try the dma ordering given to us by either the relevant
* dma code, or the board. Then just find the first usable free
* channel
*/
//根據虛擬通道號，找到一個可以的通道
//實際就是根據channel從數組s3c2440_dma_order和
//s3c2440_dma_mapping和中找到對應且可用的元素
//s3c2410_dma_request()會調用這個函數
static struct s3c2410_dma_chan *s3c2410_dma_map_channel(int channel)
{
struct s3c24xx_dma_order_ch *ord = NULL;
struct s3c24xx_dma_map *ch_map;
struct s3c2410_dma_chan *dmach;
int ch;
//dma_sel.map就是s3c2440_dma_mappings[]
//dma_sel.map_size就是ARRAY_SIZE(s3c2440_dma_mappings)
if (dma_sel.map == NULL || channel > dma_sel.map_size)
return NULL;
ch_map = dma_sel.map + channel;
//從上面這句可以看出這個channel不是指dma的4個通道
//而是s3c2440_dma_mappings[]對應的數組元素,下面有
/*channel的值如下
enum dma_ch {
DMACH_XD0,
DMACH_XD1,
DMACH_SDI,
DMACH_SPI0,
DMACH_SPI1,
DMACH_UART0,
DMACH_UART1,
...
和s3c2440_dma_mappings[]對應
*/
/* first, try the board mapping */
if (dma_order) {
ord = &dma_order->channels[channel];//找到對應的
for (ch = 0; ch < dma_channels; ch++) {
int tmp;
if (!is_channel_valid(ord->list[ch]))//判斷通道可用
continue;
tmp = ord->list[ch] & ~DMA_CH_VALID;//標誌爲不可用
//s3c2410_dma_request函數會使in_use變爲1
if (s3c2410_chans[tmp].in_use == 0) {
ch = tmp;
goto found;
}
}
if (ord->flags & DMA_CH_NEVER)
return NULL;
}
/* second, search the channel map for first free */
for (ch = 0; ch < dma_channels; ch++) {
if (!is_channel_valid(ch_map->channels[ch]))//判斷可用
continue;
if (s3c2410_chans[ch].in_use == 0) {
printk("mapped channel %d to %d\n", channel, ch);
break;
}
}
/*
上面的is_channel_valid是在平臺提供的數組中的標記
in_use是此代碼中的標記。
*/
if (ch >= dma_channels)
return NULL;
/* update our channel mapping */
found:
dmach = &s3c2410_chans[ch];
dmach->map = ch_map; //對應的struct s3c24xx_dma_map結構體
dmach->req_ch = channel;
s3c_dma_chan_map[channel] = dmach;//放入struct s3c2410_dma_chan結構體中
/* select the channel */
(dma_sel.select)(dmach, ch_map);//下面有s3c2440的select函數s3c2440_dma_select()
return dmach;
}
static int s3c24xx_dma_check_entry(struct s3c24xx_dma_map *map, int ch)
{
return 0;
}
int __init s3c24xx_dma_init_map(struct s3c24xx_dma_selection *sel)
{
//傳入的是s3c2440_dma_sel
/*
struct s3c24xx_dma_map {
const char *name;
unsigned long channels[S3C_DMA_CHANNELS];
unsigned long channels_rx[S3C_DMA_CHANNELS];
};
struct s3c24xx_dma_selection {
struct s3c24xx_dma_map *map;
unsigned long map_size;
unsigned long dcon_mask;
void (*select)(struct s3c2410_dma_chan *chan,
struct s3c24xx_dma_map *map);
void (*direction)(struct s3c2410_dma_chan *chan,
struct s3c24xx_dma_map *map,
enum dma_data_direction dir);
};
static struct s3c24xx_dma_map __initdata s3c2440_dma_mappings[] = {
[DMACH_XD0] = {
.name = "xdreq0",
.channels[0] = S3C2410_DCON_CH0_XDREQ0 | DMA_CH_VALID,
},
[DMACH_XD1] = {
.name = "xdreq1",
.channels[1] = S3C2410_DCON_CH1_XDREQ1 | DMA_CH_VALID,
},
[DMACH_SDI] = {
.name = "sdi",
.channels[0] = S3C2410_DCON_CH0_SDI | DMA_CH_VALID,
.channels[1] = S3C2440_DCON_CH1_SDI | DMA_CH_VALID,
.channels[2] = S3C2410_DCON_CH2_SDI | DMA_CH_VALID,
.channels[3] = S3C2410_DCON_CH3_SDI | DMA_CH_VALID,
},
//太長沒貼完，就是支持的外設信息
static void s3c2440_dma_select(struct s3c2410_dma_chan *chan,
struct s3c24xx_dma_map *map)
{
chan->dcon = map->channels[chan->number] & ~DMA_CH_VALID;//選擇一個通道並置爲不可用
}
static struct s3c24xx_dma_selection __initdata s3c2440_dma_sel = {
.select = s3c2440_dma_select,
.dcon_mask = 7 << 24, //dcon寄存器的24~26位 源選擇
.map = s3c2440_dma_mappings,
.map_size = ARRAY_SIZE(s3c2440_dma_mappings),
};
*/
struct s3c24xx_dma_map *nmap;
size_t map_sz = sizeof(*nmap) * sel->map_size;
int ptr;
nmap = kmalloc(map_sz, GFP_KERNEL);
if (nmap == NULL)
return -ENOMEM;
memcpy(nmap, sel->map, map_sz);
memcpy(&dma_sel, sel, sizeof(*sel));
dma_sel.map = nmap;
//上面一段就是,申請內存，把s3c2440_dma_sel的信息放入dma_sel中
for (ptr = 0; ptr < sel->map_size; ptr++)
s3c24xx_dma_check_entry(nmap+ptr, ptr);//在上面，空函數
return 0;
}
int __init s3c24xx_dma_order_set(struct s3c24xx_dma_order *ord)
{
//傳入的就是s3c2440_dma_order
/*
struct s3c24xx_dma_order_ch {
unsigned int list[S3C_DMA_CHANNELS]; // list of channels
unsigned int flags; // flags
};
struct s3c24xx_dma_order {
struct s3c24xx_dma_order_ch channels[DMACH_MAX];
};
DMACH_MAX指的是外設的最大ID,通過類似DMACH_UART0_TX來表示外設
S3C_DMA_CHANNELS是最大通道數，s3c2440是4個通道
static struct s3c24xx_dma_order __initdata s3c2440_dma_order = {
.channels = {
[DMACH_SDI] = {
.list = {
[0] = 3 | DMA_CH_VALID,
[1] = 2 | DMA_CH_VALID,
[2] = 1 | DMA_CH_VALID,
[3] = 0 | DMA_CH_VALID,
},
},
[DMACH_I2S_IN] = {
.list = {
[0] = 1 | DMA_CH_VALID,
[1] = 2 | DMA_CH_VALID,
},
},
[DMACH_I2S_OUT] = {
.list = {
[0] = 2 | DMA_CH_VALID,
[1] = 1 | DMA_CH_VALID,
},
},
[DMACH_PCM_IN] = {
.list = {
[0] = 2 | DMA_CH_VALID,
[1] = 1 | DMA_CH_VALID,
...
太多，沒貼完。
*/
struct s3c24xx_dma_order *nord = dma_order;
if (nord == NULL)//爲空的話重分配
nord = kmalloc(sizeof(struct s3c24xx_dma_order), GFP_KERNEL);
if (nord == NULL) {
printk(KERN_ERR "no memory to store dma channel order\n");
return -ENOMEM;
}
dma_order = nord;
memcpy(nord, ord, sizeof(struct s3c24xx_dma_order));
return 0;
}如果你看懂了上面的代碼，下面的plat-samsung中的代碼基本不用分析了
/* linux/arch/arm/plat-samsung/s3c-dma-ops.c
*
* Copyright (c) 2011 Samsung Electronics Co., Ltd.
* http://www.samsung.com
*
* Samsung S3C-DMA Operations
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/export.h>
#include <mach/dma.h>
struct cb_data {
void (*fp) (void *);
void *fp_param;
unsigned ch;
struct list_head node;
};
static LIST_HEAD(dma_list);
//s3c2410_dma_buffdone(chan, buf, S3C2410_RES_ABORT);
//s3c2410_dma_buffdone(chan, buf, S3C2410_RES_OK);
/*
if (chan->callback_fn != NULL) {
(chan->callback_fn)(chan, buf->id, buf->size, result);
}
*/
static void s3c_dma_cb(struct s3c2410_dma_chan *channel, void *param,
int size, enum s3c2410_dma_buffresult res)
{
struct cb_data *data = param;
data->fp(data->fp_param);
}
static unsigned s3c_dma_request(enum dma_ch dma_ch,
struct samsung_dma_info *info)
{
struct cb_data *data;
if (s3c2410_dma_request(dma_ch, info->client, NULL) < 0) {
s3c2410_dma_free(dma_ch, info->client);
return 0;
}
data = kzalloc(sizeof(struct cb_data), GFP_KERNEL);
data->ch = dma_ch;
list_add_tail(&data->node, &dma_list);
s3c2410_dma_devconfig(dma_ch, info->direction, info->fifo);
if (info->cap == DMA_CYCLIC)
s3c2410_dma_setflags(dma_ch, S3C2410_DMAF_CIRCULAR);
s3c2410_dma_config(dma_ch, info->width);
return (unsigned)dma_ch;
}
static int s3c_dma_release(unsigned ch, struct s3c2410_dma_client *client)
{
struct cb_data *data;
list_for_each_entry(data, &dma_list, node)
if (data->ch == ch)
break;
list_del(&data->node);
s3c2410_dma_free(ch, client);
kfree(data);
return 0;
}
static int s3c_dma_prepare(unsigned ch, struct samsung_dma_prep_info *info)
{
struct cb_data *data;
int len = (info->cap == DMA_CYCLIC) ? info->period : info->len;
list_for_each_entry(data, &dma_list, node)
if (data->ch == ch)
break;
if (!data->fp) {
s3c2410_dma_set_buffdone_fn(ch, s3c_dma_cb);
data->fp = info->fp;
data->fp_param = info->fp_param;
}
s3c2410_dma_enqueue(ch, (void *)data, info->buf, len);
return 0;
}
static inline int s3c_dma_trigger(unsigned ch)
{
return s3c2410_dma_ctrl(ch, S3C2410_DMAOP_START);
}
static inline int s3c_dma_started(unsigned ch)
{
return s3c2410_dma_ctrl(ch, S3C2410_DMAOP_STARTED);
}
static inline int s3c_dma_flush(unsigned ch)
{
return s3c2410_dma_ctrl(ch, S3C2410_DMAOP_FLUSH);
}
static inline int s3c_dma_stop(unsigned ch)
{
return s3c2410_dma_ctrl(ch, S3C2410_DMAOP_STOP);
}
static struct samsung_dma_ops s3c_dma_ops = {
.request = s3c_dma_request,
.release = s3c_dma_release,
.prepare = s3c_dma_prepare,
.trigger = s3c_dma_trigger,
.started = s3c_dma_started,
.flush = s3c_dma_flush,
.stop = s3c_dma_stop,
};
void *s3c_dma_get_ops(void)
{
return &s3c_dma_ops;
}
EXPORT_SYMBOL(s3c_dma_get_ops);