linux-kernel - Re: [PATCH] drm/amd/display: fix the ability to use lower resolution modes on eDP

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Date:   Thu, 14 Sep 2023 17:12:44 -0400
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     Harry Wentland <harry.wentland@....com>,
        amd-gfx@...ts.freedesktop.org
Cc:     Stylon Wang <stylon.wang@....com>, Alan Liu <haoping.liu@....com>,
        Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
        Leo Li <sunpeng.li@....com>,
        Qingqing Zhuo <Qingqing.Zhuo@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Hersen Wu <hersenxs.wu@....com>,
        dri-devel@...ts.freedesktop.org, Wayne Lin <wayne.lin@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        Joshua Ashton <joshua@...ggi.es>
Subject: Re: [PATCH] drm/amd/display: fix the ability to use lower resolution
 modes on eDP


On 9/14/23 17:04, Hamza Mahfooz wrote:
> 
> On 9/14/23 16:40, Harry Wentland wrote:
>> On 2023-09-14 13:53, Hamza Mahfooz wrote:
>>> On eDP we can receive invalid modes from dm_update_crtc_state() for
>>> entirely new streams for which drm_mode_set_crtcinfo() shouldn't be
>>> called on. So, instead of calling drm_mode_set_crtcinfo() from within
>>> create_stream_for_sink() we can instead call it from
>>> amdgpu_dm_connector_mode_valid(). Since, we are guaranteed to only call
>>> drm_mode_set_crtcinfo() for valid modes from that function (invalid
>>> modes are rejected by that callback) and that is the only user
>>> of create_validate_stream_for_sink() that we need to call
>>> drm_mode_set_crtcinfo() for (as before commit cb841d27b876
>>> ("drm/amd/display: Always pass connector_state to stream validation"),
>>> that is the only place where create_validate_stream_for_sink()'s
>>> dm_state was NULL).
>>>
>>
>> I don't seem to see how a NULL dm_state in
>> create_validate_stream_for_sink() (or create_stream_for_sink() for that
>> matter) has an impact on the drm_mode_set_crtcinfo() call. That one 
>> depends
>> on !old_stream and &mode.
> 
> If we look back to commit 4a2df0d1f28e ("drm/amd/display: Fixed
> non-native modes not lighting up") it seems like the intent was to only
> have drm_mode_set_crtcinfo() called for
> amdgpu_dm_connector_mode_valid(). Since, even if we go that far back
> create_stream_for_sink()'s dm_state was only NULL when it was called
> from amdgpu_dm_connector_mode_valid().
> 
>>
>> It does look like &mode is an empty mode if we can't find a 
>> preferred_mode,
>> though. Not sure if that can cause an issue.
> 
> I don't think it should be an issue, since before commit 4a2df0d1f28e
> ("drm/amd/display: Fixed non-native modes not lighting up") we always

I meant to refer to commit bd49f19039c1 ("drm/amd/display: Always set
crtcinfo from create_stream_for_sink") here.

> called drm_mode_set_crtcinfo() in the aforementioned case (and only for 
> that case).
> 
>>
>> Harry
>>
>>> Cc: stable@...r.kernel.org
>>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2693
>>> Fixes: cb841d27b876 ("drm/amd/display: Always pass connector_state to 
>>> stream validation")
>>> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
>>> ---
>>>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 
>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> index 933c9b5d5252..beef4fef7338 100644
>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> @@ -6128,8 +6128,6 @@ create_stream_for_sink(struct 
>>> amdgpu_dm_connector *aconnector,
>>>       if (recalculate_timing)
>>>           drm_mode_set_crtcinfo(&saved_mode, 0);
>>> -    else if (!old_stream)
>>> -        drm_mode_set_crtcinfo(&mode, 0);
>>>       /*
>>>        * If scaling is enabled and refresh rate didn't change
>>> @@ -6691,6 +6689,8 @@ enum drm_mode_status 
>>> amdgpu_dm_connector_mode_valid(struct drm_connector *connec
>>>           goto fail;
>>>       }
>>> +    drm_mode_set_crtcinfo(mode, 0);
>>> +
>>>       stream = create_validate_stream_for_sink(aconnector, mode,
>>>                            to_dm_connector_state(connector->state),
>>>                            NULL);
>>
-- 
Hamza