【30】sys文件系統熱插拔的流程（poweron poweroff）

pciehp_probe->pci_hp_add->fs_add_slot會創建對應的slot



我們去/sys/bus/pci/slots中看看每個slot的address，對應的root port都是我們預留出來支持熱插拔的

cat power就會調用的power_read_file
static struct pci_slot_attribute hotplug_slot_attr_power = {
	.attr = {.name = "power", .mode = S_IFREG | S_IRUGO | S_IWUSR},
	.show = power_read_file,
	.store = power_write_file
};
static ssize_t power_read_file(struct pci_slot *pci_slot, char *buf)
{
	int retval;
	u8 value;

	retval = get_power_status(pci_slot->hotplug, &value);
	if (retval)
		return retval;

	return sprintf(buf, "%d\n", value);
}
static int get_power_status(struct hotplug_slot *hotplug_slot, u8 *value)
{
	struct controller *ctrl = to_ctrl(hotplug_slot);
	struct pci_dev *pdev = ctrl->pcie->port;

	pci_config_pm_runtime_get(pdev);
	pciehp_get_power_status(ctrl, value);
	pci_config_pm_runtime_put(pdev);
	return 0;
}
void pciehp_get_power_status(struct controller *ctrl, u8 *status)
{
	struct pci_dev *pdev = ctrl_dev(ctrl);
	u16 slot_ctrl;

	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl);
	ctrl_dbg(ctrl, "%s: SLOTCTRL %x value read %x\n", __func__,
		 pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL, slot_ctrl);

	switch (slot_ctrl & PCI_EXP_SLTCTL_PCC) {
	case PCI_EXP_SLTCTL_PWR_ON:
		*status = 1;	/* On */
		break;
	case PCI_EXP_SLTCTL_PWR_OFF:
		*status = 0;	/* Off */
		break;
	default:
		*status = 0xFF;
		break;
	}
#define  PCI_EXP_SLTCTL_PWR_ON         0x0000 /* Power On */
#define  PCI_EXP_SLTCTL_PWR_OFF        0x0400 /* Power Off */

echo 1 > power或者echo 0 > power就會power_write_file，最終會上下電對應slot
static ssize_t power_write_file(struct pci_slot *pci_slot, const char *buf,
				size_t count)
{
	struct hotplug_slot *slot = pci_slot->hotplug;
	unsigned long lpower;
	u8 power;
	int retval = 0;

	lpower = simple_strtoul(buf, NULL, 10);
	power = (u8)(lpower & 0xff);
	dbg("power = %d\n", power);

	if (!try_module_get(slot->owner)) {
		retval = -ENODEV;
		goto exit;
	}
	switch (power) {
	case 0:
		if (slot->ops->disable_slot)
			retval = slot->ops->disable_slot(slot);
		break;

	case 1:
		if (slot->ops->enable_slot)
			retval = slot->ops->enable_slot(slot);
		break;

	default:
		err("Illegal value specified for power\n");
		retval = -EINVAL;
	}
	module_put(slot->owner);

exit:
	if (retval)
		return retval;
	return count;
}
init_slot時會把對應OPS賦值給ctrl->hotplug_slot.ops
static int init_slot(struct controller *ctrl)
{
	struct hotplug_slot_ops *ops;
	char name[SLOT_NAME_SIZE];
	int retval;

	/* Setup hotplug slot ops */
	ops = kzalloc(sizeof(*ops), GFP_KERNEL);
	if (!ops)
		return -ENOMEM;

	ops->enable_slot = pciehp_sysfs_enable_slot;
	ops->disable_slot = pciehp_sysfs_disable_slot;
	ops->get_power_status = get_power_status;
	ops->get_adapter_status = get_adapter_status;
	ops->reset_slot = pciehp_reset_slot;
	if (MRL_SENS(ctrl))
		ops->get_latch_status = get_latch_status;
	if (ATTN_LED(ctrl)) {
		ops->get_attention_status = pciehp_get_attention_status;
		ops->set_attention_status = set_attention_status;
	} else if (ctrl->pcie->port->hotplug_user_indicators) {
		ops->get_attention_status = pciehp_get_raw_indicator_status;
		ops->set_attention_status = pciehp_set_raw_indicator_status;
	}

	/* register this slot with the hotplug pci core */
	ctrl->hotplug_slot.ops = ops;
	snprintf(name, SLOT_NAME_SIZE, "%u", PSN(ctrl));

	retval = pci_hp_initialize(&ctrl->hotplug_slot,
				   ctrl->pcie->port->subordinate, 0, name);
	if (retval) {
		ctrl_err(ctrl, "pci_hp_initialize failed: error %d\n", retval);
		kfree(ops);
	}
	return retval;
}


int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot)
{
	struct controller *ctrl = to_ctrl(hotplug_slot);

	mutex_lock(&ctrl->state_lock);
	switch (ctrl->state) {
	case BLINKINGON_STATE:
	case OFF_STATE:
		mutex_unlock(&ctrl->state_lock);
		/*
		 * The IRQ thread becomes a no-op if the user pulls out the
		 * card before the thread wakes up, so initialize to -ENODEV.
		 */
		ctrl->request_result = -ENODEV;
		pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
		wait_event(ctrl->requester,
			   !atomic_read(&ctrl->pending_events));
		return ctrl->request_result;
	case POWERON_STATE:
		ctrl_info(ctrl, "Slot(%s): Already in powering on state\n",
			  slot_name(ctrl));
		break;
	case BLINKINGOFF_STATE:
	case ON_STATE:
	case POWEROFF_STATE:
		ctrl_info(ctrl, "Slot(%s): Already enabled\n",
			  slot_name(ctrl));
		break;
	default:
		ctrl_err(ctrl, "Slot(%s): Invalid state %#x\n",
			 slot_name(ctrl), ctrl->state);
		break;
	}
	mutex_unlock(&ctrl->state_lock);

	return -ENODEV;
}
pciehp_sysfs_disable_slot會調用pciehp_request把DISABLE_SLOT添加到pending_event，
然後喚醒線程ctrl->pcie->irq
int pciehp_sysfs_disable_slot(struct hotplug_slot *hotplug_slot)
{
	struct controller *ctrl = to_ctrl(hotplug_slot);

	mutex_lock(&ctrl->state_lock);
	switch (ctrl->state) {
	case BLINKINGOFF_STATE:
	case ON_STATE:
		mutex_unlock(&ctrl->state_lock);
		pciehp_request(ctrl, DISABLE_SLOT);
		wait_event(ctrl->requester,
			   !atomic_read(&ctrl->pending_events));
		return ctrl->request_result;
	case POWEROFF_STATE:
		ctrl_info(ctrl, "Slot(%s): Already in powering off state\n",
			  slot_name(ctrl));
		break;
	case BLINKINGON_STATE:
	case OFF_STATE:
	case POWERON_STATE:
		ctrl_info(ctrl, "Slot(%s): Already disabled\n",
			  slot_name(ctrl));
		break;
	default:
		ctrl_err(ctrl, "Slot(%s): Invalid state %#x\n",
			 slot_name(ctrl), ctrl->state);
		break;
	}
	mutex_unlock(&ctrl->state_lock);

	return -ENODEV;
}

void pciehp_request(struct controller *ctrl, int action)
{
	atomic_or(action, &ctrl->pending_events);
	if (!pciehp_poll_mode)
		irq_wake_thread(ctrl->pcie->irq, ctrl);
}

pciehp_probe->pcie_init_notification->pciehp_request_irq
可以看到註冊了irq處理線程pciehp_ist
static inline int pciehp_request_irq(struct controller *ctrl)
{
	int retval, irq = ctrl->pcie->irq;

	if (pciehp_poll_mode) {
		ctrl->poll_thread = kthread_run(&pciehp_poll, ctrl,
						"pciehp_poll-%s",
						slot_name(ctrl));
		return PTR_ERR_OR_ZERO(ctrl->poll_thread);
	}

	/* Installs the interrupt handler */
	retval = request_threaded_irq(irq, pciehp_isr, pciehp_ist,
				      IRQF_SHARED, "pciehp", ctrl);
	if (retval)
		ctrl_err(ctrl, "Cannot get irq %d for the hotplug controller\n",
			 irq);
	return retval;
}

pciehp_ist取出DISABLE_SLOT的事件，調用pciehp_handle_disable_request
->pciehp_disable_slot->__pciehp_disable_slot

__pciehp_disable_slot獲取電源狀態，如果已經下電就返回，否者調用remove_board
static int __pciehp_disable_slot(struct controller *ctrl, bool safe_removal)
{
	u8 getstatus = 0;

	if (POWER_CTRL(ctrl)) {
		pciehp_get_power_status(ctrl, &getstatus);
		if (!getstatus) {
			ctrl_info(ctrl, "Slot(%s): Already disabled\n",
				  slot_name(ctrl));
			return -EINVAL;
		}
	}

	remove_board(ctrl, safe_removal);
	return 0;
}

remove_board檢查是否支持下電，支持則調用pciehp_power_off_slot
寫配置空間下電，然後ignore因爲下單引起的data link change和presence change中斷
（這裏其實是併發的，這樣做不保險，保險的做法是禁止中斷，等下電完畢，然後清除中斷狀態）
static void remove_board(struct controller *ctrl, bool safe_removal)
{
	pciehp_unconfigure_device(ctrl, safe_removal);

	if (POWER_CTRL(ctrl)) {
		pciehp_power_off_slot(ctrl);

		/*
		 * After turning power off, we must wait for at least 1 second
		 * before taking any action that relies on power having been
		 * removed from the slot/adapter.
		 */
		msleep(1000);

		/* Ignore link or presence changes caused by power off */
		atomic_and(~(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC),
			   &ctrl->pending_events);
	}

	pciehp_set_indicators(ctrl, PCI_EXP_SLTCTL_PWR_IND_OFF,
			      INDICATOR_NOOP);
}
pciehp_power_off_slot寫配置空間下電
void pciehp_power_off_slot(struct controller *ctrl)
{
	pcie_write_cmd(ctrl, PCI_EXP_SLTCTL_PWR_OFF, PCI_EXP_SLTCTL_PCC);
	ctrl_dbg(ctrl, "%s: SLOTCTRL %x write cmd %x\n", __func__,
		 pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL,
		 PCI_EXP_SLTCTL_PWR_OFF);
}

主要我們操作sys文件系統中的對應節點就可以上下電slot，獲取adapter的在位狀態等。