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

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Message-ID: <vhqmcb6fu6mfmbjo3jyjdhzpowhvnxbtxg2osk42xwogrsylku@5hvs6mtizqcr>
Date: Thu, 9 Jan 2025 06:22:38 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
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 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")

> 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)
> > 

-- 
With best wishes
Dmitry