[PATCH] drm/amdgpu: don't call drm_fb_helper_lastclose in lastclose()

[Thomas Zimmermann]

Hi

Am 24.10.22 um 18:48 schrieb Alex Deucher:
> On Mon, Oct 24, 2022 at 3:33 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>>
>> Hi
>>
>> Am 24.10.22 um 08:20 schrieb Quan, Evan:
>>> [AMD Official Use Only - General]
>>>
>>> Reviewed-by: Evan Quan <evan.quan at amd.com>
>>>
>>>> -----Original Message-----
>>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Alex
>>>> Deucher
>>>> Sent: Thursday, October 20, 2022 10:36 PM
>>>> To: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
>>>> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Thomas
>>>> Zimmermann <tzimmermann at suse.de>
>>>> Subject: [PATCH] drm/amdgpu: don't call drm_fb_helper_lastclose in
>>>> lastclose()
>>>>
>>>> It's used to restore the fbdev console, but as amdgpu uses
>>>> generic fbdev emulation, the console is being restored by the
>>>> DRM client helpers already. See the call to drm_client_dev_restore()
>>>> in drm_lastclose().
>>>>
>>>> Fixes: 087451f372bf76 ("drm/amdgpu: use generic fb helpers instead of
>>>> setting up AMD own's.")
>>>> Cc: Thomas Zimmermann <tzimmermann at suse.de>
>>>> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 1 -
>>>>    1 file changed, 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>>> index fe23e09eec98..474b9f40f792 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>>> @@ -1106,7 +1106,6 @@ int amdgpu_info_ioctl(struct drm_device *dev,
>>>> void *data, struct drm_file *filp)
>>>>     */
>>>>    void amdgpu_driver_lastclose_kms(struct drm_device *dev)
>>>>    {
>>>> -    drm_fb_helper_lastclose(dev);
>>>>       vga_switcheroo_process_delayed_switch();
>>>>    }
>>
>> Without the call to drm_fb_helper_lastclose(), the console emulation
>> will be restored by drm_client_dev_restore() from drm_lastclose(). [1]
>> It means that it's now changing order with the call to
>> vga_switcheroo_process_delay_switch(). Can this become a problem?
>>
>> I looked at the other callers of that function. Most restore the console
>> before doing the switcheroo. Nouveau doesn't seem to care about the
>> console at all.
> 
> I don't know off hand.  I suppose if the switch powered down the GPU
> and then we tried to restore it's console state that would be a
> problem, but it looks like vga_switchto_stage2() just powers down the
> GPU without going through suspend so I'm not sure if this actually
> worked correctly?  What are the potential problems with calling
> drm_fb_helper_lastclose twice?

It should do fbdev console modesetting twice; so no problem.

AFAIU calling vga switcheroo does nothing for devices without support. 
So let's call vga_switcheroo_process_delayed_switch() at the very end of 
drm_lastclose() and remove the amdgpu callback entirely. [1]  This 
should not be a problem and if, we can refactor the whole function.

Best regards
Thomas

[1] 
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_file.c#L468

> 
> Alex
> 
>>
>> Best regards
>> Thomas
>>
>> [1]
>> https://elixir.bootlin.com/linux/v6.0.3/source/drivers/gpu/drm/drm_file.c#L467
>>
>>>>
>>>> --
>>>> 2.37.3
>>
>> --
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Ivo Totev

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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