| Message ID | 201209112238.06658.rjw@sisk.pl (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Tue, Sep 11, 2012 at 10:38:06PM +0200, Rafael J. Wysocki wrote: > It turns out that there are ACPI BIOSes defining device objects with > _PSx and without either _PSC or _PRx. For devices corresponding to > those ACPI objetcs __acpi_bus_get_power() returns ACPI_STATE_UNKNOWN > and their initial power states are regarded as unknown as a result. > If such a device is a parent of another power-manageable device, the > child cannot be put into a low-power state through ACPI, because > __acpi_bus_set_power() refuses to change power states of devices > whose parents' power states are unknown. > > To work around this problem, observe that the ACPI power state of > a device cannot be higher-power (lower-number) than the power state > of its parent. Thus, if the device's _PSC method or the > configuration of its power resources indicates that the device is > in D0, the device's parent has to be in D0 as well. Consequently, > if the parent's power state is unknown when we've just learned that > its child's power state is D0, we can safely set the parent's > power.state field to ACPI_STATE_D0. > > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Tested-by: Aaron Lu <aaron.lu@intel.com> -Aaron > --- > drivers/acpi/bus.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > Index: linux/drivers/acpi/bus.c > =================================================================== > --- linux.orig/drivers/acpi/bus.c > +++ linux/drivers/acpi/bus.c > @@ -237,6 +237,16 @@ static int __acpi_bus_get_power(struct a > } else if (result == ACPI_STATE_D3_HOT) { > result = ACPI_STATE_D3; > } > + > + /* > + * If we were unsure about the device parent's power state up to this > + * point, the fact that the device is in D0 implies that the parent has > + * to be in D0 too. > + */ > + if (device->parent && device->parent->power.state == ACPI_STATE_UNKNOWN > + && result == ACPI_STATE_D0) > + device->parent->power.state = ACPI_STATE_D0; > + > *state = result; > > out: -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Index: linux/drivers/acpi/bus.c =================================================================== --- linux.orig/drivers/acpi/bus.c +++ linux/drivers/acpi/bus.c @@ -237,6 +237,16 @@ static int __acpi_bus_get_power(struct a } else if (result == ACPI_STATE_D3_HOT) { result = ACPI_STATE_D3; } + + /* + * If we were unsure about the device parent's power state up to this + * point, the fact that the device is in D0 implies that the parent has + * to be in D0 too. + */ + if (device->parent && device->parent->power.state == ACPI_STATE_UNKNOWN + && result == ACPI_STATE_D0) + device->parent->power.state = ACPI_STATE_D0; + *state = result; out:
It turns out that there are ACPI BIOSes defining device objects with _PSx and without either _PSC or _PRx. For devices corresponding to those ACPI objetcs __acpi_bus_get_power() returns ACPI_STATE_UNKNOWN and their initial power states are regarded as unknown as a result. If such a device is a parent of another power-manageable device, the child cannot be put into a low-power state through ACPI, because __acpi_bus_set_power() refuses to change power states of devices whose parents' power states are unknown. To work around this problem, observe that the ACPI power state of a device cannot be higher-power (lower-number) than the power state of its parent. Thus, if the device's _PSC method or the configuration of its power resources indicates that the device is in D0, the device's parent has to be in D0 as well. Consequently, if the parent's power state is unknown when we've just learned that its child's power state is D0, we can safely set the parent's power.state field to ACPI_STATE_D0. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> --- drivers/acpi/bus.c | 10 ++++++++++ 1 file changed, 10 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html