[PATCH] drm/amdgpu: Fix S3 resume failre.

[Andrey Grodzovsky]

On 07/19/2018 12:47 PM, Michel Dänzer wrote:
> On 2018-07-19 06:33 PM, Andrey Grodzovsky wrote:
>> On 07/19/2018 11:39 AM, Ville Syrjälä wrote:
>>> On Thu, Jul 19, 2018 at 11:19:56AM -0400, Andrey Grodzovsky wrote:
>>>> Problem:
>>>> FB is still not unpinned during the first run of amdgpu_bo_evict_vram
>>>> and so it's left for the second run, but during second run the SDMA for
>>>> moving buffer around already disabled and you have to do
>>>> it with CPU, but FB is not in visible VRAM and hence the eviction
>>>> failure
>>>> leading later to resume failure.
>>>>
>>>> Fix:
>>>> When DAL in use get a pointer to FB from crtc->primary->state rather
>>>> then from crtc->primary which is not set for DAL since it supports
>>>> atomic KMS.
>>>>
>>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107065
>>>> Fixes e00fb85 drm: Stop updating plane->crtc/fb/old_fb on atomic drivers
>>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 3 ++-
>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> index 709e4a3..dd9ebf7 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> @@ -2642,7 +2642,8 @@ int amdgpu_device_suspend(struct drm_device
>>>> *dev, bool suspend, bool fbcon)
>>>>        /* unpin the front buffers and cursors */
>>>>        list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
>>>>            struct amdgpu_crtc *amdgpu_crtc = to_amdgpu_crtc(crtc);
>>>> -        struct drm_framebuffer *fb = crtc->primary->fb;
>>>> +         struct drm_framebuffer *fb =
>>>> amdgpu_device_has_dc_support(adev) ?
>>>> +                 crtc->primary->state->fb : crtc->primary->fb;
>>> So apparently you haven't yet turned off the planes here. If I'm
>>> reading things right amdgpu_device_ip_suspend() should end up doing
>>> that through drm_atomic_helper_suspend(). So it looks like like now
>>> you'll end up unpinning the same bos twice. Doesn't that mess up
>>> some kind of refcount or something?
>> amdgpu_bo_unpin has a guard against that, amdgpu_bo_unreserve is less
>> clear.
> BO reservation shouldn't an issue here, BOs are only reserved for a
> short time around (un)pinning them.
>
>
>>> To me it would seem better to susped the display before trying
>>> to evict the bos.
>> Yea, i was aware of that and indeed DAL shouldn't rely on the code in
>> amdgpu_device_suspend to unpin
>> front buffer and cursor since the atomic helper should do it. Problem is
>> that during amdgpu_device_ip_suspend
>> the SDMA engine gets suspended too, so you have to embed another
>> eviction in between, after display is suspended but before
>> SDMA and this forces ordering between them which kind of already in
>> place (amd_ip_block_type) but still it's an extra constrain.
> Ville's point (which I basically agree with) is that the display
> hardware should be turned off before evicting VRAM the first time, in
> which case no second eviction should be necessary (for this purpose).

Display HW is turned off as part of all IPs in a loop inside 
amdgpu_device_ip_suspend.
Are you suggesting to extract the  display HW turn off from inside 
amdgpu_device_ip_suspend and place it
before the first call to amdgpu_bo_evict_vram ?

Andrey

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