On Wednesday, August 31, 2016 08:15:18 AM Lukas Wunner wrote:
> Usually the most accurate way to determine a PCI device's power state is
> to read its PM Control & Status Register. There are two cases however
> when this is not an option: If the device doesn't have the PM
> capability at all, or if it is in D3cold.
>
> In D3cold, reading from config space typically results in a fabricated
> "all ones" response. But in D3hot, the two bits representing the power
> state in the PMCSR are *also* set to 1. Thus D3hot and D3cold are not
> discernible by just reading the PMCSR.
>
> A (supposedly) reliable way to detect D3cold is to query the platform
> firmware for its opinion on the device's power state. To this end,
> add a ->get_power callback to struct pci_platform_pm_ops, and an
> implementation to acpi_pci_platform_pm. (The only pci_platform_pm_ops
> existing so far).
>
> Amend pci_update_current_state() to query the platform firmware before
> reading the PMCSR.
>
> Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
> ---
> drivers/pci/pci-acpi.c | 23 +++++++++++++++++++++++
> drivers/pci/pci.c | 21 ++++++++++++++++-----
> drivers/pci/pci.h | 3 +++
> 3 files changed, 42 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 9a033e8..89f2707 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -452,6 +452,28 @@ static int acpi_pci_set_power_state(struct pci_dev *dev, pci_power_t state)
> return error;
> }
>
> +static pci_power_t acpi_pci_get_power_state(struct pci_dev *dev)
> +{
> + struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
> + static const pci_power_t state_conv[] = {
> + [ACPI_STATE_D0] = PCI_D0,
> + [ACPI_STATE_D1] = PCI_D1,
> + [ACPI_STATE_D2] = PCI_D2,
> + [ACPI_STATE_D3_HOT] = PCI_D3hot,
> + [ACPI_STATE_D3_COLD] = PCI_D3cold,
> + };
> + int state;
ACPI_STATE_D3_HOT and ACPI_STATE_D3_COLD were introduced in ACPI 4.0. For
systems predating that, ACPI_STATE_D3_HOT is the deepest state returned by
acpi_device_get_power().
> +
> + if (!adev || !acpi_device_power_manageable(adev))
> + return PCI_UNKNOWN;
> +
> + if (acpi_device_get_power(adev, &state) || state < ACPI_STATE_D0
> + || state > ACPI_STATE_D3_COLD)
If the device is power-manageable by ACPI (you've just checked that) and
acpi_device_get_power() returns success (0), the returned state is guaranteed
to be within the boundaries (if it isn't, there is a bug that needs to be fixed).
> + return PCI_UNKNOWN;
> +
> + return state_conv[state];
> +}
> +
> static bool acpi_pci_can_wakeup(struct pci_dev *dev)
> {
> struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
> @@ -534,6 +556,7 @@ static bool acpi_pci_need_resume(struct pci_dev *dev)
> static const struct pci_platform_pm_ops acpi_pci_platform_pm = {
> .is_manageable = acpi_pci_power_manageable,
> .set_state = acpi_pci_set_power_state,
> + .get_state = acpi_pci_get_power_state,
> .choose_state = acpi_pci_choose_state,
> .sleep_wake = acpi_pci_sleep_wake,
> .run_wake = acpi_pci_run_wake,
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 72a9d3a..e52e3d4 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -552,8 +552,9 @@ static const struct pci_platform_pm_ops *pci_platform_pm;
>
> int pci_set_platform_pm(const struct pci_platform_pm_ops *ops)
> {
> - if (!ops->is_manageable || !ops->set_state || !ops->choose_state ||
> - !ops->sleep_wake || !ops->run_wake || !ops->need_resume)
> + if (!ops->is_manageable || !ops->set_state || !ops->get_state ||
> + !ops->choose_state || !ops->sleep_wake || !ops->run_wake ||
> + !ops->need_resume)
> return -EINVAL;
> pci_platform_pm = ops;
> return 0;
> @@ -570,6 +571,11 @@ static inline int platform_pci_set_power_state(struct pci_dev *dev,
> return pci_platform_pm ? pci_platform_pm->set_state(dev, t) : -ENOSYS;
> }
>
> +static inline pci_power_t platform_pci_get_power_state(struct pci_dev *dev)
> +{
> + return pci_platform_pm ? pci_platform_pm->get_state(dev) : PCI_UNKNOWN;
> +}
> +
> static inline pci_power_t platform_pci_choose_state(struct pci_dev *dev)
> {
> return pci_platform_pm ?
> @@ -701,14 +707,19 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
> }
>
> /**
> - * pci_update_current_state - Read PCI power state of given device from its
> - * PCI PM registers and cache it
> + * pci_update_current_state - Read power state of given device and cache it
> * @dev: PCI device to handle.
> * @state: State to cache in case the device doesn't have the PM capability
> + *
> + * The power state is read from the PMCSR register, which however is
> + * inaccessible in D3cold. The platform firmware is therefore queried first
> + * to detect accessibility of the register.
> */
> void pci_update_current_state(struct pci_dev *dev, pci_power_t state)
> {
> - if (dev->pm_cap) {
> + if (platform_pci_get_power_state(dev) == PCI_D3cold) {
> + dev->current_state = PCI_D3cold;
> + } else if (dev->pm_cap) {
Why exactly do you need to change this function?
> u16 pmcsr;
>
> /*
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 9730c47..01d5206 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -42,6 +42,8 @@ int pci_probe_reset_function(struct pci_dev *dev);
> *
> * @set_state: invokes the platform firmware to set the device's power state
> *
> + * @get_state: queries the platform firmware for a device's current power state
> + *
> * @choose_state: returns PCI power state of given device preferred by the
> * platform; to be used during system-wide transitions from a
> * sleeping state to the working state and vice versa
> @@ -62,6 +64,7 @@ int pci_probe_reset_function(struct pci_dev *dev);
> struct pci_platform_pm_ops {
> bool (*is_manageable)(struct pci_dev *dev);
> int (*set_state)(struct pci_dev *dev, pci_power_t state);
> + pci_power_t (*get_state)(struct pci_dev *dev);
> pci_power_t (*choose_state)(struct pci_dev *dev);
> int (*sleep_wake)(struct pci_dev *dev, bool enable);
> int (*run_wake)(struct pci_dev *dev, bool enable);
>
Thanks,
Rafael
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