linux-kernel - Re: [PATCH 3/6] drm/msm/dpu: don't use active in atomic

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Message-ID: <a8159ad0-3d33-4331-899c-6728862a728a@quicinc.com>
Date: Wed, 8 Jan 2025 21:37:23 -0800
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard
	<mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        Chandan Uddaraju <chandanu@...eaurora.org>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        Jordan Crouse
	<jordan@...micpenguin.net>,
        Sravanthi Kollukuduru <skolluku@...eaurora.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Archit
 Taneja <architt@...eaurora.org>,
        Rajesh Yadav <ryadav@...eaurora.org>, <linux-arm-msm@...r.kernel.org>,
        <freedreno@...ts.freedesktop.org>,
        Simona
 Vetter <simona.vetter@...ll.ch>
Subject: Re: [PATCH 3/6] drm/msm/dpu: don't use active in atomic_check()



On 1/8/2025 8:22 PM, Dmitry Baryshkov wrote:
> On Wed, Jan 08, 2025 at 05:19:40PM -0800, Abhinav Kumar wrote:
>>
>>
>> On 12/21/2024 9:00 PM, Dmitry Baryshkov wrote:
>>> The driver isn't supposed to consult crtc_state->active/active_check for
>>> resource allocation. Instead all resources should be allocated if
>>> crtc_state->enabled is set. Stop consulting active / active_changed in
>>> order to determine whether the hardware resources should be
>>> (re)allocated.
>>>
>>> Fixes: 25fdd5933e4c ("drm/msm: Add SDM845 DPU support")
>>> Reported-by: Simona Vetter <simona.vetter@...ll.ch>
>>> Closes: https://lore.kernel.org/dri-devel/ZtW_S0j5AEr4g0QW@phenom.ffwll.local/
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>> ---
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c    | 4 ----
>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 3 +--
>>>    2 files changed, 1 insertion(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>> index 7191b1a6d41b3a96f956d199398f12b2923e8c82..65e33eba61726929b740831c95330756b2817e28 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>> @@ -1264,10 +1264,6 @@ static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
>>>    	DRM_DEBUG_ATOMIC("%s: check\n", dpu_crtc->name);
>>> -	/* force a full mode set if active state changed */
>>> -	if (crtc_state->active_changed)
>>> -		crtc_state->mode_changed = true;
>>> -
>>>    	if (cstate->num_mixers) {
>>>    		rc = _dpu_crtc_check_and_setup_lm_bounds(crtc, crtc_state);
>>>    		if (rc)
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>> index 83de7564e2c1fe14fcf8c4f82335cafc937e1b99..d1ccdca6044353f110bf5b507788efe368f223a3 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>> @@ -793,12 +793,11 @@ static int dpu_encoder_virt_atomic_check(
>>>    		crtc_state->mode_changed = true;
>>>    	/*
>>>    	 * Release and Allocate resources on every modeset
>>> -	 * Dont allocate when active is false.
>>>    	 */
>>>    	if (drm_atomic_crtc_needs_modeset(crtc_state)) {
>>>    		dpu_rm_release(global_state, drm_enc);
>>> -		if (!crtc_state->active_changed || crtc_state->enable)
>>
>> I think this was leftover code.
>>
>> What happened was, we used to have dpu_rm_reserve() both in dpu_encoder's
>> atomic_check and mode_set. Hence this is checking !active_changed because
>> that case was expected to get handled in mode_set to avoid duplicate
>> dpu_rm_reserve() calls. Code has progressed since then to drop the
>> dpu_rm_reserve() from mode_set and only use atomic_check.
>>
>> So the correct fixes tag for this should be:
>>
>> Fixes: de3916c70a24 ("drm/msm/dpu: Track resources in global state")
> 
> Actually it should be:
> 
> Fixes: ccc862b957c6 ("drm/msm/dpu: Fix reservation failures in modeset")
> 

Ack.

>> With that addressed, this is
>>
>> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
>>
>>> +		if (crtc_state->enable)
>>>    			ret = dpu_rm_reserve(&dpu_kms->rm, global_state,
>>>    					drm_enc, crtc_state, topology);
>>>    		if (!ret)
>>>
>