On Tue, 2012-05-15 at 20:48 +0200, Rafael J. Wysocki wrote:
> 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@xxxxxxxxx>
> > ---
> > 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.
Sure. Will change this.
Best Regards,
Huang Ying
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