[PATCH 1/2] drm/amd/display: increase max surfaces in line with planes and streams

[Melissa Wen]

On 23/10/2024 17:36, Mohamed, Zaeem wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
>
> Hi,
>
> A patch addressing this will be sent out soon.
Great! Thanks for the heads up!

Melissa
>
> Thanks,
> Zaeem
>
> -----Original Message-----
> From: Melissa Wen <mwen at igalia.com>
> Sent: Tuesday, October 22, 2024 11:58 AM
> To: Mohamed, Zaeem <Zaeem.Mohamed at amd.com>; Wentland, Harry <Harry.Wentland at amd.com>; Li, Sun peng (Leo) <Sunpeng.Li at amd.com>; Siqueira, Rodrigo <Rodrigo.Siqueira at amd.com>; Deucher, Alexander <Alexander.Deucher at amd.com>; Koenig, Christian <Christian.Koenig at amd.com>; Pan, Xinhui <Xinhui.Pan at amd.com>; airlied at gmail.com; daniel at ffwll.ch
> Cc: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
> Subject: Re: [PATCH 1/2] drm/amd/display: increase max surfaces in line with planes and streams
>
> Hi,
>
> Gentle ping to land the fix for the kernel crash.
> If faster, I can send a new version increasing max surfaces to 4 as previously discussed.
>
> There are now two bug reports for the same issue:
> - https://gitlab.freedesktop.org/drm/amd/-/issues/3693
> - https://gitlab.freedesktop.org/drm/amd/-/issues/3594
>
> Best Regards,
>
> Melissa
>
>
> On 27/09/2024 15:20, Melissa Wen wrote:
>> Hi Zaeem,
>>
>> Thanks for explaining their relationship.
>>
>> So IIUC, current DM implementation for dc_surface_updates array is
>> wrong, since it's taking MAX_SURFACES (=3) for allocation but
>> MAX_PLANES (=6) as the upper bound of size of the dc_surface_updates
>> array, as you can see in this allocation and after an iteration from 0
>> to `plane_count`:
>>
>> https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/amd/disp
>> lay/amdgpu_dm/amdgpu_dm.c#L9861
>>
>>
>> Another question to understand what would be the right fix for the
>> implementation above-mentioned: with the cursor overlay mode, it means
>> we are using one of the overlay planes for this cursor overlay mode
>> (one from the "max_slave_planes") or this cursor plane is an extra
>> plane, which means, for some drivers, one primary plane + two overlay
>> planes + one plane for cursor overlay mode (max 4 planes) ?
>>
>> BR,
>>
>> Melissa
>>
>> On 27/09/2024 14:40, Mohamed, Zaeem wrote:
>>> [AMD Official Use Only - AMD Internal Distribution Only]
>>>
>>> Hi Melissa,
>>>
>>> MAX_SURFACE_NUM and MAX_PLANES both represent the upper bound of
>>> planes that are supported by HW. It is best to replace
>>> MAX_SURFACE_NUM with MAX_PLANES to remove redundancy. MAX_SURFACES is
>>> used to represent the upper bound of surfaces that can be piped to a
>>> single CRTC. Keep MAX_SURFACES as is to keep stack size down, and
>>> replace MAX_SURFACE_NUM with MAX_PLANES.
>>>
>>> Thanks,
>>> Zaeem
>>>
>>>
>>> -----Original Message-----
>>> From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf
>>> Of Melissa Wen
>>> Sent: Wednesday, September 25, 2024 11:37 AM
>>> To: harry.wentland at amd.com; sunpeng.li at amd.com;
>>> Rodrigo.Siqueira at amd.com; alexander.deucher at amd.com;
>>> christian.koenig at amd.com; Xinhui.Pan at amd.com; airlied at gmail.com;
>>> daniel at ffwll.ch
>>> Cc: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
>>> Subject: [PATCH 1/2] drm/amd/display: increase max surfaces in line
>>> with planes and streams
>>>
>>> 091a97e542cf ("drm/amd/display: Fix warning. Set MAX_SURFACES to 3")
>>> reduced the max number of surfaces since, at that time, there was no
>>> use for more. However, HW and driver evolves and there are now driver
>>> versions that allow two overlay planes (max_slave_planes). Moreover,
>>> commit 3cfd03b79425 ("drm/amd/display: update max streams per
>>> surface") states 6 is the max surfaces supported asics can have.
>>> Therefore, update MAX_SURFACES to match MAX_SURFACE_NUM, MAX_PLANES
>>> and MAX_STREAMS.
>>>
>>> It also addresses array-index-out-of-bounds reported in the link.
>>>
>>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3594
>>> Signed-off-by: Melissa Wen <mwen at igalia.com>
>>> ---
>>>    drivers/gpu/drm/amd/display/dc/dc.h | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/display/dc/dc.h
>>> b/drivers/gpu/drm/amd/display/dc/dc.h
>>> index 3992ad73165b..08b00b263533 100644
>>> --- a/drivers/gpu/drm/amd/display/dc/dc.h
>>> +++ b/drivers/gpu/drm/amd/display/dc/dc.h
>>> @@ -57,7 +57,7 @@ struct dmub_notification;
>>>
>>>    #define DC_VER "3.2.301"
>>>
>>> -#define MAX_SURFACES 3
>>> +#define MAX_SURFACES 6
>>>    #define MAX_PLANES 6
>>>    #define MAX_STREAMS 6
>>>    #define MIN_VIEWPORT_SIZE 12
>>> --
>>> 2.45.2
>>>