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Date: Tue, 15 May 2012 20:48:08 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Huang Ying <ying.huang@...el.com>
Cc: Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org,
linux-acpi@...r.kernel.org
Subject: Re: [PATCH 1/5] ACPI, PM, Specify lowest allowed state for device sleep state
On Tuesday, May 15, 2012, Huang Ying wrote:
> Lower device sleep state can save more power, but has more exit
> latency too. Sometimes, to satisfy some power QoS and other
> requirement, we need to constrain the lowest device sleep state.
>
> In this patch, a parameter to specify lowest allowed state for
> acpi_pm_device_sleep_state is added. So that the caller can enforce
> the constraint via the parameter.
>
> This is needed by PCIe D3cold support, where the lowest power state
> allowed may be D3_HOT instead of default D3_COLD.
>
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> ---
> drivers/acpi/sleep.c | 24 +++++++++++++++++++-----
> drivers/pci/pci-acpi.c | 3 ++-
> drivers/pnp/pnpacpi/core.c | 4 ++--
> include/acpi/acpi_bus.h | 6 +++---
> 4 files changed, 26 insertions(+), 11 deletions(-)
>
> --- a/drivers/acpi/sleep.c
> +++ b/drivers/acpi/sleep.c
> @@ -677,8 +677,9 @@ int acpi_suspend(u32 acpi_state)
> * @dev: device to examine; its driver model wakeup flags control
> * whether it should be able to wake up the system
> * @d_min_p: used to store the upper limit of allowed states range
> - * Return value: preferred power state of the device on success, -ENODEV on
> - * failure (ie. if there's no 'struct acpi_device' for @dev)
> + * @d_max_in: specify the lowest allowed states
> + * Return value: preferred power state of the device on success, -ENODEV
> + * (ie. if there's no 'struct acpi_device' for @dev) or -EINVAL on failure
> *
> * Find the lowest power (highest number) ACPI device power state that
> * device @dev can be in while the system is in the sleep state represented
> @@ -693,13 +694,15 @@ int acpi_suspend(u32 acpi_state)
> * via @wake.
> */
>
> -int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p)
> +int acpi_pm_device_sleep_state(struct device *dev, int *d_min_p, int d_max_in)
> {
> acpi_handle handle = DEVICE_ACPI_HANDLE(dev);
> struct acpi_device *adev;
> char acpi_method[] = "_SxD";
> unsigned long long d_min, d_max;
>
> + if (d_max_in < ACPI_STATE_D0 || d_max_in > ACPI_STATE_D3)
> + return -EINVAL;
> if (!handle || ACPI_FAILURE(acpi_bus_get_device(handle, &adev))) {
> printk(KERN_DEBUG "ACPI handle has no context!\n");
> return -ENODEV;
> @@ -707,8 +710,10 @@ int acpi_pm_device_sleep_state(struct de
>
> acpi_method[2] = '0' + acpi_target_sleep_state;
> /*
> - * If the sleep state is S0, we will return D3, but if the device has
> - * _S0W, we will use the value from _S0W
> + * If the sleep state is S0, the lowest limit from ACPI is D3,
> + * but if the device has _S0W, we will use the value from _S0W
> + * as the lowest limit from ACPI. Finally, we will constrain
> + * the lowest limit with the specified one.
> */
> d_min = ACPI_STATE_D0;
> d_max = ACPI_STATE_D3;
> @@ -754,6 +759,15 @@ int acpi_pm_device_sleep_state(struct de
>
> if (d_min_p)
> *d_min_p = d_min;
> + if (d_max_in < d_min)
> + return -EINVAL;
This check should go before the modification of the variable pointed to by
d_min_p, so that we don't change things in case the error code is returned.
Apart from this, the patch looks good to me.
> + /* constrain d_max with specified lowest limit (max number) */
> + if (d_max > d_max_in) {
> + for (d_max = d_max_in; d_max > d_min; d_max--) {
> + if (adev->power.states[d_max].flags.valid)
> + break;
> + }
> + }
> return d_max;
> }
> #endif /* CONFIG_PM */
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -189,7 +189,8 @@ static pci_power_t acpi_pci_choose_state
> {
> int acpi_state;
>
> - acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL);
> + acpi_state = acpi_pm_device_sleep_state(&pdev->dev, NULL,
> + ACPI_STATE_D3);
> if (acpi_state < 0)
> return PCI_POWER_ERROR;
>
> --- a/drivers/pnp/pnpacpi/core.c
> +++ b/drivers/pnp/pnpacpi/core.c
> @@ -170,8 +170,8 @@ static int pnpacpi_suspend(struct pnp_de
> }
>
> if (acpi_bus_power_manageable(handle)) {
> - int power_state = acpi_pm_device_sleep_state(&dev->dev, NULL);
> -
> + int power_state = acpi_pm_device_sleep_state(&dev->dev, NULL,
> + ACPI_STATE_D3);
> if (power_state < 0)
> power_state = (state.event == PM_EVENT_ON) ?
> ACPI_STATE_D0 : ACPI_STATE_D3;
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -383,13 +383,13 @@ int acpi_enable_wakeup_device_power(stru
> int acpi_disable_wakeup_device_power(struct acpi_device *dev);
>
> #ifdef CONFIG_PM
> -int acpi_pm_device_sleep_state(struct device *, int *);
> +int acpi_pm_device_sleep_state(struct device *, int *, int);
> #else
> -static inline int acpi_pm_device_sleep_state(struct device *d, int *p)
> +static inline int acpi_pm_device_sleep_state(struct device *d, int *p, int m)
> {
> if (p)
> *p = ACPI_STATE_D0;
> - return ACPI_STATE_D3;
> + return (m >= ACPI_STATE_D0 && <= ACPI_STATE_D3) ? m : ACPI_STATE_D0;
> }
> #endif
Thanks,
Rafael
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