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Wysocki" , lenb@kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230704074506.2304939-1-kai.heng.feng@canonical.com> Content-Language: en-US From: Hans de Goede In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 7/6/23 10:20, Kai-Heng Feng wrote: > On Wed, Jul 5, 2023 at 6:33 PM Hans de Goede wrote: >> >> Hi, >> >> On 7/4/23 18:58, Rafael J. Wysocki wrote: >>> On Tue, Jul 4, 2023 at 9:46 AM Kai-Heng Feng >>> wrote: >>>> >>>> Screen brightness can only be changed once on some HP laptops. >>>> >>>> Vendor identified the root cause as Linux doesn't invoke _PS0 at boot >>>> for all ACPI devices: >>> >>> This part of the changelog is confusing, because the evaluation of >>> _PS0 is not a separate operation. _PS0 gets evaluated when devices >>> undergo transitions from low-power states to D0. >>> >>>> Scope (\_SB.PC00.GFX0) >>>> { >>>> Scope (DD1F) >>>> { >>>> Method (_PS0, 0, Serialized) // _PS0: Power State 0 >>>> { >>>> If (CondRefOf (\_SB.PC00.LPCB.EC0.SSBC)) >>>> { >>>> \_SB.PC00.LPCB.EC0.SSBC () >>>> } >>>> } >>>> ... >>>> } >>>> ... >>>> } >>>> >>>> _PS0 doesn't get invoked for all ACPI devices because of commit >>>> 7cd8407d53ef ("ACPI / PM: Do not execute _PS0 for devices without _PSC >>>> during initialization"). >> >> So this _PS0 which seems to be the one which needs to run here, >> is not the _PS0 for the GFX0 ACPI device, but rather for a child ACPI device-node which describes the connector (assumed based on the small part of quoted DSDT, the actual definition of the DD1F device-node is missing). > > I'll file a bugzilla and attach a full acpidump there. > >> >> Having a _PS0 method on a connector object is really weird IMHO. But if we need to invoke such a _PS0 method then IMHO that really should be done in the drm/kms driver. E.g. at least the i915 code already contains code to map the ACPI connector objects to the drm_connector objects, so it should be relatively easily to make that try and do a power-transition to D0 when enabling the connector. > > Or put all ACPI devices to D0 at boot? > According to the BIOS folks that's what Windows does. > This way we can drop acpi_device_fix_up_power* helpers altogether. Doing that will leave any devices for which we lack a driver at D0 for ever, so that IMHO is not a good idea. I guess calling acpi_device_fix_up_power_extended(device) from the ACPI-video code, so that the connector sub-objects are put in D0 is somewhat ok. Although I would prefer to see you first try to do the same thing from the i915 driver instead. If we do end up doing this from the acpi-video code please add a comment above the call why this is done; and as Rafael mentioned the commit msg needs to better explain things too. Regards, Hans > >> >> Also can you provide some more info on the hw on which this is being seen: >> >> 1. What GPU(s) is/are being used > > Intel GFX. > > AFAIK AMD based laptops also require this fixup too. > >> 2. If there is a mux for hybrid gfx in which mode is the mux set ? > > No. This happens to mux-less and dGPU-less laptops. > >> 3. Wjich method is used to control the brightness (which backlight-class-devices show up under /sys/class/backlight) ? > > intel_backlight. > >> >> And can you add this info to the commit msg for the next version of the patch ? > > Sure. > Can putting all devices to D0 be considered too? It's a better > solution for the long wrong. > > Kai-Heng > >> >> Regards, >> >> Hans >> >> >> >> >>> >>> And yes, Linux doesn't put all of the ACPI devices into D0 during >>> initialization, but the above commit has a little to do with that. >>> >>>> For now explicitly call _PS0 for ACPI video to workaround the issue. >>> >>> This is not what the patch is doing. >>> >>>> Signed-off-by: Kai-Heng Feng >>>> --- >>>> drivers/acpi/acpi_video.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c >>>> index 62f4364e4460..793259bd18c8 100644 >>>> --- a/drivers/acpi/acpi_video.c >>>> +++ b/drivers/acpi/acpi_video.c >>>> @@ -2027,6 +2027,8 @@ static int acpi_video_bus_add(struct acpi_device *device) >>>> if (error) >>>> goto err_put_video; >>>> >>>> + acpi_device_fix_up_power_extended(device); >>>> + >>> >>> I would like to know what Hans thinks about this. >>> >>>> pr_info("%s [%s] (multi-head: %s rom: %s post: %s)\n", >>>> ACPI_VIDEO_DEVICE_NAME, acpi_device_bid(device), >>>> video->flags.multihead ? "yes" : "no", >>>> -- >>> >> >