Re: [RFC v2 5/5] PCIe, Add PCIe runtime D3cold support

[huang ying <huang.ying.caritas@gmail.com>]

On Sat, May 5, 2012 at 3:51 AM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> On Fri, May 4, 2012 at 2:13 AM, Huang Ying <ying.huang@intel.com> 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@intel.com>
>> Signed-off-by: Huang Ying <ying.huang@intel.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
>> +                */ at
>> +               if (pci_dev->subordinate)
>> +                       count = pci_wakeup_bus(pci_dev->subordinate);
>> +               if (count == 0)
>> +                       pm_runtime_resume(&pci_dev->dev);
>> +               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;
>>
>>        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;
>>                        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);
>> +       }
>> +       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;
>> +
>>        __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;
>
> We don't care what the previous state of info->power_must_be_on was,
> so to me, this would read more naturally as:
>
>    if (pdev->dev.power.power_must_be_on)
>        info->power_must_be_on = true;

OK.  Will change this.

>> +       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.
>> +        */
>> +       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;
>
> Maybe you've thought about how this works in the presence of hot-added
> devices below pdev, but it's not obvious to me that it's safe to cache
> power_must_be_on and d3cold_delay in the struct device and struct
> pci_dev.  Are they guaranteed to be updated when a new device is
> hot-added?

The power_must_be_on and d3cold_delay will be updated when a device is
going to be runtime suspended, and used during the runtime
suspend/resume cycle.  I think when we hot-add a new device, we should
runtime resume all its parents firstly.  Doesn't it?

Best Regards,
Huang Ying