| Message ID | 1831630.tdWV9SEqCh@kreacher |
|---|---|
| State | New |
| Headers | show |
| Series | drm: amd: amdgpu: ACPI: Add comment about ACPI_FADT_LOW_POWER_S0 | expand |
On 8/24/2022 12:32, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > According to the ACPI specification [1], the ACPI_FADT_LOW_POWER_S0 > flag merely means that it is better to use low-power S0 idle on the > given platform than S3 (provided that the latter is supported) and it > doesn't preclude using either of them (which of them will be used > depends on the choices made by user space). > > However, on some systems that flag is used to indicate whether or not > to enable special firmware mechanics allowing the system to save more > energy when suspended to idle. If that flag is unset, doing so is > generally risky. > > Accordingly, add a comment to explain the ACPI_FADT_LOW_POWER_S0 check > in amdgpu_acpi_is_s0ix_active(), the purpose of which is otherwise > somewhat unclear. > > Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fuefi.org%2Fspecs%2FACPI%2F6.4%2F05_ACPI_Software_Programming_Model%2FACPI_Software_Programming_Model.html%23fixed-acpi-description-table-fadt&data=05%7C01%7Cmario.limonciello%40amd.com%7Cf43320dda5114deeb16908da85f69d3b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637969591512297179%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=xp8pNzsXCkLcIJOJFY77yaLkMrvz5he3S%2Bi%2FwaxTwwg%3D&reserved=0 # [1] > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > Index: linux-pm/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c > =================================================================== > --- linux-pm.orig/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c > +++ linux-pm/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c > @@ -1066,6 +1066,12 @@ bool amdgpu_acpi_is_s0ix_active(struct a > (pm_suspend_target_state != PM_SUSPEND_TO_IDLE)) > return false; > > + /* > + * If ACPI_FADT_LOW_POWER_S0 is not set in the FADT, it is generally > + * risky to do any special firmware-related preparations for entering > + * S0ix even though the system is suspending to idle, so return false > + * in that case. > + */ > if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) { > dev_warn_once(adev->dev, > "Power consumption will be higher as BIOS has not been configured for suspend-to-idle.\n" > > >
Applied. Thanks! Alex On Thu, Aug 25, 2022 at 3:58 AM Limonciello, Mario <mario.limonciello@amd.com> wrote: > > On 8/24/2022 12:32, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > According to the ACPI specification [1], the ACPI_FADT_LOW_POWER_S0 > > flag merely means that it is better to use low-power S0 idle on the > > given platform than S3 (provided that the latter is supported) and it > > doesn't preclude using either of them (which of them will be used > > depends on the choices made by user space). > > > > However, on some systems that flag is used to indicate whether or not > > to enable special firmware mechanics allowing the system to save more > > energy when suspended to idle. If that flag is unset, doing so is > > generally risky. > > > > Accordingly, add a comment to explain the ACPI_FADT_LOW_POWER_S0 check > > in amdgpu_acpi_is_s0ix_active(), the purpose of which is otherwise > > somewhat unclear. > > > > Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fuefi.org%2Fspecs%2FACPI%2F6.4%2F05_ACPI_Software_Programming_Model%2FACPI_Software_Programming_Model.html%23fixed-acpi-description-table-fadt&data=05%7C01%7Cmario.limonciello%40amd.com%7Cf43320dda5114deeb16908da85f69d3b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637969591512297179%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=xp8pNzsXCkLcIJOJFY77yaLkMrvz5he3S%2Bi%2FwaxTwwg%3D&reserved=0 # [1] > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> > > > --- > > drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > Index: linux-pm/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c > > =================================================================== > > --- linux-pm.orig/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c > > +++ linux-pm/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c > > @@ -1066,6 +1066,12 @@ bool amdgpu_acpi_is_s0ix_active(struct a > > (pm_suspend_target_state != PM_SUSPEND_TO_IDLE)) > > return false; > > > > + /* > > + * If ACPI_FADT_LOW_POWER_S0 is not set in the FADT, it is generally > > + * risky to do any special firmware-related preparations for entering > > + * S0ix even though the system is suspending to idle, so return false > > + * in that case. > > + */ > > if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) { > > dev_warn_once(adev->dev, > > "Power consumption will be higher as BIOS has not been configured for suspend-to-idle.\n" > > > > > > >
Index: linux-pm/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c =================================================================== --- linux-pm.orig/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c +++ linux-pm/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c @@ -1066,6 +1066,12 @@ bool amdgpu_acpi_is_s0ix_active(struct a (pm_suspend_target_state != PM_SUSPEND_TO_IDLE)) return false; + /* + * If ACPI_FADT_LOW_POWER_S0 is not set in the FADT, it is generally + * risky to do any special firmware-related preparations for entering + * S0ix even though the system is suspending to idle, so return false + * in that case. + */ if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) { dev_warn_once(adev->dev, "Power consumption will be higher as BIOS has not been configured for suspend-to-idle.\n"