linux-kernel - Re: [PATCH] drm/msm/dpu: filter out too wide modes if no 3dmux is present

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Message-ID: <b784049f-a72c-47ff-a618-e7c85c132d28@quicinc.com>
Date: Mon, 9 Dec 2024 12:07:28 -0800
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn
 Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/dpu: filter out too wide modes if no 3dmux is
 present



On 12/7/2024 9:29 PM, Dmitry Baryshkov wrote:
> On Fri, Dec 06, 2024 at 12:00:53PM -0800, Abhinav Kumar wrote:
>> On chipsets such as QCS615, there is no 3dmux present. In such
>> a case, a layer exceeding the max_mixer_width cannot be split,
>> hence cannot be supported.
>>
>> Filter out the modes which exceed the max_mixer_width when there
>> is no 3dmux present. Also, add a check in the dpu_crtc_atomic_check()
>> to return failure for such modes.
>>
>> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
>> ---
>> Note: this was only compile tested, so its pending validation on QCS615
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> index 9f6ffd344693ecfb633095772a31ada5613345dc..e6e5540aae83be7c20d8ae29115b8fdd42056e55 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> @@ -732,6 +732,13 @@ static int _dpu_crtc_check_and_setup_lm_bounds(struct drm_crtc *crtc,
>>   	struct dpu_kms *dpu_kms = _dpu_crtc_get_kms(crtc);
>>   	int i;
>>   
>> +	/* if we cannot merge 2 LMs (no 3d mux) better to fail earlier
>> +	 * before even checking the width after the split
>> +	 */
>> +	if (!dpu_kms->catalog->caps->has_3d_merge
>> +	    && adj_mode->hdisplay > dpu_kms->catalog->caps->max_mixer_width)
>> +		return -E2BIG;
> 
> Is it the same as checking that there are LMs which support
> DPU_MIXER_SOURCESPLIT ?
> 

DPU_MIXER_SOURCESPLIT tells whether we can have more than one SSPP in 
the same blend stage.

494 	if (test_bit(DPU_MIXER_SOURCESPLIT,
495 		&ctx->mixer_hw_caps->features))
496 		pipes_per_stage = PIPES_PER_STAGE;
497 	else
498 		pipes_per_stage = 1;

That is different from this one. Here we are checking if we can actually 
blend two LM outputs using the 3dmux (so its post blend).

>> +
>>   	for (i = 0; i < cstate->num_mixers; i++) {
>>   		struct drm_rect *r = &cstate->lm_bounds[i];
>>   		r->x1 = crtc_split_width * i;
>> @@ -1251,6 +1258,12 @@ static enum drm_mode_status dpu_crtc_mode_valid(struct drm_crtc *crtc,
>>   {
>>   	struct dpu_kms *dpu_kms = _dpu_crtc_get_kms(crtc);
>>   
>> +	/* if there is no 3d_mux block we cannot merge LMs so we cannot
>> +	 * split the large layer into 2 LMs, filter out such modes
>> +	 */
>> +	if (!dpu_kms->catalog->caps->has_3d_merge
>> +	    && mode->hdisplay > dpu_kms->catalog->caps->max_mixer_width)
>> +		return MODE_BAD;
> 
> This can be more specific, like MODE_BAD_HVALUE.
> 

Yes for sure, will fix this up.

>>   	/*
>>   	 * max crtc width is equal to the max mixer width * 2 and max height is 4K
>>   	 */
>>
>> ---
>> base-commit: af2ea8ab7a546b430726183458da0a173d331272
>> change-id: 20241206-no_3dmux-521a55ea0669
>>
>> Best regards,
>> -- 
>> Abhinav Kumar <quic_abhinavk@...cinc.com>
>>
>