Date:	Fri, 4 May 2012 22:50:39 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, ming.m.lin@...el.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Zheng Yan <zheng.z.yan@...el.com>
Subject: Re: [RFC v2 5/5] PCIe, Add PCIe runtime D3cold support

On Friday, May 04, 2012, Huang Ying wrote:
> This patch adds runtime D3cold support to PCIe bus.  D3cold is the
> deepest power saving state for PCIe devices.  Where the main PCIe link
> will be powered off totally, so before the PCIe main link is powered
> on again, you can not access the device, even the configuration space,
> which is still accessible in D3hot.  Because the main PCIe link is not
> available, the PCI PM registers can not be used to put device into/out
> of D3cold state, that will be done by platform logic such as ACPI
> _PR3.
> 
> To support remote wake up in D3cold, aux power is supplied, and a
> side-band pin: WAKE# is used to notify remote wake up event, the pin
> is usually connected to platform logic such as ACPI GPE.  This is
> quite different with other power saving states, where remote wake up
> is notified via PME message via the PCIe main link.
> 
> PCIe devices in plug-in slot usually has no direct platform logic, for
> example, there is usually no ACPI _PR3 for them.  The D3cold support
> for these devices can be done via the PCIe port connected to it.  When
> power on/off the PCIe port, the corresponding PCIe devices are powered
> on/off too.  And the remote wake up event from PCIe device will be
> notified to the corresponding PCIe port.
> 
> The PCI subsystem D3cold support and corresponding ACPI platform
> support is implemented in the patch.  Including the support for PCIe
> devices in plug-in slot.
> 
> For more information about PCIe D3cold and corresponding ACPI support,
> please refer to:
> 
> - PCI Express Base Specification Revision 2.0
> - Advanced Configuration and Power Interface Specification Revision 5.0
> 
> Originally-by: Zheng Yan <zheng.z.yan@...el.com>
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> ---
>  drivers/pci/pci-acpi.c         |   32 +++++++++--
>  drivers/pci/pci-driver.c       |    3 +
>  drivers/pci/pci.c              |  115 +++++++++++++++++++++++++++++++++++++----
>  drivers/pci/pci.h              |    1 
>  drivers/pci/pcie/portdrv_pci.c |   28 +++++++++
>  include/linux/pci.h            |   12 +++-
>  6 files changed, 175 insertions(+), 16 deletions(-)
> 
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -48,6 +48,21 @@ static void pci_acpi_wake_dev(acpi_handl
>  	if (event != ACPI_NOTIFY_DEVICE_WAKE || !pci_dev)
>  		return;
>  
> +	if (pci_dev->current_state == PCI_D3cold) {
> +		unsigned int count = 0;
> +
> +		/*
> +		 * Powering on bridge need to resume whole hierarchy,
> +		 * just resume the children to avoid the bridge going
> +		 * suspending as soon as resumed
> +		 */

Don't you need to resume the bridge before you start walking the hierarchy
below it?

> +		if (pci_dev->subordinate)
> +			count = pci_wakeup_bus(pci_dev->subordinate);
> +		if (count == 0)
> +			pm_runtime_resume(&pci_dev->dev);

What's the count for, exactly?

> +		return;
> +	}
> +
>  	if (!pci_dev->pm_cap || !pci_dev->pme_support
>  	     || pci_check_pme_status(pci_dev)) {
>  		if (pci_dev->pme_poll)
> @@ -187,10 +202,13 @@ acpi_status pci_acpi_remove_pm_notifier(
>  
>  static pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
>  {
> -	int acpi_state;
> +	int acpi_state, d_max;
>  
> -	acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL,
> -						ACPI_STATE_D3);
> +	if (pdev->dev.power.power_must_be_on)
> +		d_max = ACPI_STATE_D3_HOT;
> +	else
> +		d_max = ACPI_STATE_D3_COLD;
> +	acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL, d_max);
>  	if (acpi_state < 0)
>  		return PCI_POWER_ERROR;
>  
> @@ -297,7 +315,13 @@ static void acpi_pci_propagate_run_wake(
>  
>  static int acpi_pci_run_wake(struct pci_dev *dev, bool enable)
>  {
> -	if (dev->pme_interrupt)
> +	/*
> +	 * Per PCI Express Base Specification Revision 2.0 section
> +	 * 5.3.3.2 Link Wakeup, platform support is needed for D3cold
> +	 * waking up to power on the main link even if there is PME
> +	 * support for D3cold
> +	 */
> +	if (dev->pme_interrupt && !dev->runtime_d3cold)
>  		return 0;
>  
>  	if (!acpi_pm_device_run_wake(&dev->dev, enable))
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1013,10 +1013,13 @@ static int pci_pm_runtime_suspend(struct
>  	if (!pm || !pm->runtime_suspend)
>  		return -ENOSYS;
>  
> +	dev->power.power_must_be_on = false;
>  	error = pm->runtime_suspend(dev);
>  	suspend_report_result(pm->runtime_suspend, error);
>  	if (error)
>  		return error;
> +	if (!dev->power.power_off_user)
> +		dev->power.power_must_be_on = true;

That doesn't look good.  The flag itself should be exported via sysfs, but
only if it is known that power can be removed from the device.

>  
>  	pci_fixup_device(pci_fixup_suspend, pci_dev);
>  
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -653,6 +653,12 @@ void pci_update_current_state(struct pci
>  	if (dev->pm_cap) {
>  		u16 pmcsr;
>  
> +		/*
> +		 * Configuration space is not accessible for device in
> +		 * D3cold, so keep in D3cold for safety
> +		 */
> +		if (dev->current_state == PCI_D3cold)
> +			return;
>  		pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
>  		dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
>  	} else {
> @@ -671,8 +677,11 @@ static int pci_platform_power_transition
>  
>  	if (platform_pci_power_manageable(dev)) {
>  		error = platform_pci_set_power_state(dev, state);
> -		if (!error)
> +		if (!error) {
> +			if (state == PCI_D3cold)
> +				dev->current_state = PCI_D3cold;

+			else ?

>  			pci_update_current_state(dev, state);
>
> +		}
>  		/* Fall back to PCI_D0 if native PM is not supported */
>  		if (!dev->pm_cap)
>  			dev->current_state = PCI_D0;
> @@ -693,8 +702,49 @@ static int pci_platform_power_transition
>   */
>  static void __pci_start_power_transition(struct pci_dev *dev, pci_power_t state)
>  {
> -	if (state == PCI_D0)
> +	if (state == PCI_D0) {
>  		pci_platform_power_transition(dev, PCI_D0);
> +		/*
> +		 * Mandatory power management transition delays, see
> +		 * PCI Express Base Specification Revision 2.0 Section
> +		 * 6.6.1: Conventional Reset.  Do not delay for
> +		 * devices powered on/off by corresponding bridge,
> +		 * because have already delayed for the bridge.
> +		 */
> +		if (dev->runtime_d3cold) {
> +			msleep(dev->d3cold_delay);
> +			/* When powering on a bridge from D3cold, the
> +			 * whole hierarchy may be powered on into
> +			 * D0uninitialized state, resume them to give
> +			 * them a chance to suspend again */
> +			if (dev->subordinate)
> +				pci_wakeup_bus(dev->subordinate);
> +		}
> +	}
> +}
> +
> +/**
> + * __pci_dev_set_current_state - Set current state of a PCI device
> + * @dev: Device to handle
> + * @data: pointer to state to be set
> + */
> +static int __pci_dev_set_current_state(struct pci_dev *dev, void *data)
> +{
> +	pci_power_t state = *(pci_power_t *)data;
> +
> +	dev->current_state = state;
> +	return 0;
> +}
> +
> +/**
> + * __pci_bus_set_current_state - Walk given bus and set current state of devices
> + * @bus: Top bus of the subtree to walk.
> + * @state: state to be set
> + */
> +static void __pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state)
> +{
> +	if (bus)
> +		pci_walk_bus(bus, __pci_dev_set_current_state, &state);
>  }
>  
>  /**
> @@ -706,8 +756,17 @@ static void __pci_start_power_transition
>   */
>  int __pci_complete_power_transition(struct pci_dev *dev, pci_power_t state)
>  {
> -	return state >= PCI_D0 ?
> -			pci_platform_power_transition(dev, state) : -EINVAL;
> +	int ret;
> +
> +	if (state < PCI_D0)
> +		return -EINVAL;
> +	ret = pci_platform_power_transition(dev, state);
> +	if (!ret && state == PCI_D3cold) {
> +		/* Power off the bridge may power off the whole hierarchy */
> +		if (dev->subordinate)
> +			__pci_bus_set_current_state(dev->subordinate, state);

I'd just say

+			__pci_bus_set_current_state(dev->subordinate, PCI_D3cold);

here.  Also you don't need the if (dev->subordinate) check, because
__pci_bus_set_current_state() will do it anyway.

> +	}
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(__pci_complete_power_transition);
>  
> @@ -731,8 +790,8 @@ int pci_set_power_state(struct pci_dev *
>  	int error;
>  
>  	/* bound the state we're entering */
> -	if (state > PCI_D3hot)
> -		state = PCI_D3hot;
> +	if (state > PCI_D3cold)
> +		state = PCI_D3cold;
>  	else if (state < PCI_D0)
>  		state = PCI_D0;
>  	else if ((state == PCI_D1 || state == PCI_D2) && pci_no_d1d2(dev))
> @@ -747,10 +806,15 @@ int pci_set_power_state(struct pci_dev *
>  
>  	/* This device is quirked not to be put into D3, so
>  	   don't put it in D3 */
> -	if (state == PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
> +	if (state >= PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
>  		return 0;
>
> -	error = pci_raw_set_power_state(dev, state);
> +	/*
> +	 * To put device in D3cold, we put device into D3hot in native
> +	 * way, then put device into D3cold with platform ops
> +	 */
> +	error = pci_raw_set_power_state(dev, state > PCI_D3hot ?
> +					PCI_D3hot : state);
>  
>  	if (!__pci_complete_power_transition(dev, state))
>  		error = 0;
> @@ -1506,6 +1570,34 @@ void pci_pme_wakeup_bus(struct pci_bus *
>  }
>  
>  /**
> + * pci_wakeup - Wake up a PCI device
> + * @dev: Device to handle.
> + * @data: to count how many device are waken up.
> + */
> +static int pci_wakeup(struct pci_dev *dev, void *data)
> +{
> +	unsigned int *count = data;
> +
> +	pci_wakeup_event(dev);
> +	pm_request_resume(&dev->dev);
> +	(*count)++;
> +	return 0;
> +}
> +
> +/**
> + * pci_wakeup_bus - Walk given bus and wake up devices on it
> + * @bus: Top bus of the subtree to walk.
> + */
> +unsigned int pci_wakeup_bus(struct pci_bus *bus)
> +{
> +	unsigned int count = 0;
> +
> +	if (bus)
> +		pci_walk_bus(bus, pci_wakeup, &count);
> +	return count;
> +}
> +
> +/**
>   * pci_pme_capable - check the capability of PCI device to generate PME#
>   * @dev: PCI device to handle.
>   * @state: PCI state from which device will issue PME#.
> @@ -1789,12 +1881,16 @@ int pci_finish_runtime_suspend(struct pc
>  	if (target_state == PCI_POWER_ERROR)
>  		return -EIO;
>  
> +	dev->runtime_d3cold = target_state == PCI_D3cold ? true : false;

+	dev->runtime_d3cold = target_state == PCI_D3cold;

will suffice.

> +
>  	__pci_enable_wake(dev, target_state, true, pci_dev_run_wake(dev));
>  
>  	error = pci_set_power_state(dev, target_state);
>  
> -	if (error)
> +	if (error) {
>  		__pci_enable_wake(dev, target_state, true, false);
> +		dev->runtime_d3cold = false;
> +	}
>  
>  	return error;
>  }
> @@ -1864,6 +1960,7 @@ void pci_pm_init(struct pci_dev *dev)
>  
>  	dev->pm_cap = pm;
>  	dev->d3_delay = PCI_PM_D3_WAIT;
> +	dev->d3cold_delay = PCI_PM_D3COLD_WAIT;
>  
>  	dev->d1_support = false;
>  	dev->d2_support = false;
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -70,6 +70,7 @@ extern void pci_update_current_state(str
>  extern void pci_disable_enabled_device(struct pci_dev *dev);
>  extern int pci_finish_runtime_suspend(struct pci_dev *dev);
>  extern int __pci_pme_wakeup(struct pci_dev *dev, void *ign);
> +extern unsigned int pci_wakeup_bus(struct pci_bus *bus);
>  extern void pci_pm_init(struct pci_dev *dev);
>  extern void platform_pci_wakeup_init(struct pci_dev *dev);
>  extern void pci_allocate_cap_save_buffers(struct pci_dev *dev);
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -101,10 +101,38 @@ static int pcie_port_resume_noirq(struct
>  }
>  
>  #ifdef CONFIG_PM_RUNTIME
> +struct d3cold_info {
> +	bool power_must_be_on;
> +	unsigned int d3cold_delay;
> +};
> +
> +static int pci_dev_d3cold_info(struct pci_dev *pdev, void *data)
> +{
> +	struct d3cold_info *info = data;
> +
> +	info->d3cold_delay = max_t(unsigned int, pdev->d3cold_delay,
> +				   info->d3cold_delay);
> +	info->power_must_be_on = info->power_must_be_on ||
> +		pdev->dev.power.power_must_be_on;
> +	return 0;
> +}
> +
>  static int pcie_port_runtime_suspend(struct device *dev)
>  {
>  	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct d3cold_info d3cold_info = {
> +		.power_must_be_on	= dev->power.power_must_be_on,
> +		.d3cold_delay		= PCI_PM_D3_WAIT,
> +	};
>  
> +	/*
> +	 * If any subordinate device need to keep power on, we should
> +	 * not power off the port.  The D3cold delay of port should be
> +	 * the max of that of all subordinate devices.

What if some of the devices below the port are ports themselves?  Or PCI-to-PCIe
bridges?

> +	 */
> +	pci_walk_bus(pdev->subordinate, pci_dev_d3cold_info, &d3cold_info);
> +	dev->power.power_must_be_on = d3cold_info.power_must_be_on;
> +	pdev->d3cold_delay = d3cold_info.d3cold_delay;
>  	pci_save_state(pdev);
>  	return 0;
>  }
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -132,9 +132,10 @@ static inline const char *pci_power_name
>  	return pci_power_names[1 + (int) state];
>  }
>  
> -#define PCI_PM_D2_DELAY	200
> -#define PCI_PM_D3_WAIT	10
> -#define PCI_PM_BUS_WAIT	50
> +#define PCI_PM_D2_DELAY		200
> +#define PCI_PM_D3_WAIT		10
> +#define PCI_PM_D3COLD_WAIT	100
> +#define PCI_PM_BUS_WAIT		50
>  
>  /** The pci_channel state describes connectivity between the CPU and
>   *  the pci device.  If some PCI bus between here and the pci device
> @@ -282,7 +283,12 @@ struct pci_dev {
>  	unsigned int	mmio_always_on:1;	/* disallow turning off io/mem
>  						   decoding during bar sizing */
>  	unsigned int	wakeup_prepared:1;
> +	unsigned int	runtime_d3cold:1;	/* whether go through runtime
> +						   D3cold, not set for devices
> +						   powered on/off by the
> +						   corresponding bridge */
>  	unsigned int	d3_delay;	/* D3->D0 transition time in ms */
> +	unsigned int	d3cold_delay;	/* D3cold->D0 transition time in ms */
>  
>  #ifdef CONFIG_PCIEASPM
>  	struct pcie_link_state	*link_state;	/* ASPM link state. */

Thanks,
Rafael
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