linux-kernel - Re: [PATCH 6/7] drm/msm/dpu: allocate single CTL for DPU >= 5.0

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Message-ID: <d4chicea6vhlbvw23lclnqovlhq4rfdtefkk66vnbo5y3wf5y4@ajrutdjao2e2>
Date: Mon, 24 Feb 2025 15:39:10 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Marijn Suijten <marijn.suijten@...ainline.org>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 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 6/7] drm/msm/dpu: allocate single CTL for DPU >= 5.0

On Mon, Feb 24, 2025 at 01:38:22PM +0100, Marijn Suijten wrote:
> On 2025-02-21 01:58:58, Dmitry Baryshkov wrote:
> > On Fri, Feb 21, 2025 at 12:34:12AM +0100, Marijn Suijten wrote:
> > > On 2025-02-20 12:26:23, Dmitry Baryshkov wrote:
> > > > Unlike previous generation, since DPU 5.0 it is possible to use just one
> > > > CTL to handle all INTF and WB blocks for a single output. And one has to
> > > > use single CTL to support bonded DSI config. Allocate single CTL for
> > > > these DPU versions.
> > > > 
> > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > > > ---
> > > >  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 17 +++++++++++++----
> > > >  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h |  2 ++
> > > >  2 files changed, 15 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > > > index 5baf9df702b84b74ba00e703ad3cc12afb0e94a4..4dbc9bc7eb4f151f83055220665ee5fd238ae7ba 100644
> > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > > > @@ -53,6 +53,8 @@ int dpu_rm_init(struct drm_device *dev,
> > > >  	/* Clear, setup lists */
> > > >  	memset(rm, 0, sizeof(*rm));
> > > >  
> > > > +	rm->has_legacy_ctls = (cat->mdss_ver->core_major_ver < 5);
> > > > +
> > > >  	/* Interrogate HW catalog and create tracking items for hw blocks */
> > > >  	for (i = 0; i < cat->mixer_count; i++) {
> > > >  		struct dpu_hw_mixer *hw;
> > > > @@ -381,10 +383,16 @@ static int _dpu_rm_reserve_ctls(
> > > >  	int i = 0, j, num_ctls;
> > > >  	bool needs_split_display;
> > > >  
> > > > -	/* each hw_intf needs its own hw_ctrl to program its control path */
> > > > -	num_ctls = top->num_intf;
> > > > +	if (rm->has_legacy_ctls) {
> > > > +		/* each hw_intf needs its own hw_ctrl to program its control path */
> > > > +		num_ctls = top->num_intf;
> > > >  
> > > > -	needs_split_display = _dpu_rm_needs_split_display(top);
> > > > +		needs_split_display = _dpu_rm_needs_split_display(top);
> > > > +	} else {
> > > > +		/* use single CTL */
> > > > +		num_ctls = 1;
> > > > +		needs_split_display = false;
> > > > +	}
> > > >  
> > > >  	for (j = 0; j < ARRAY_SIZE(rm->ctl_blks); j++) {
> > > >  		const struct dpu_hw_ctl *ctl;
> > > > @@ -402,7 +410,8 @@ static int _dpu_rm_reserve_ctls(
> > > >  
> > > >  		DPU_DEBUG("ctl %d caps 0x%lX\n", j + CTL_0, features);
> > > >  
> > > > -		if (needs_split_display != has_split_display)
> > > > +		if (rm->has_legacy_ctls &&
> > > > +		    needs_split_display != has_split_display)
> > > 
> > > I deduced a long time ago that the check for rm->has_legacy_ctls is not needed.
> > > 
> > > needs_split_display is always false on DPU >= 5, and neither of those SoCs has
> > > DPU_CTRL_SPLIT_DISPLAY which means false != false is false, and this condition
> > > never triggers on active CTLs even without checking has_legacy_ctls.
> > 
> > During the transition time of 1 or 2 patches there is a window of
> > DPU >= 5 and DPU_CTRL_SPLIT_DISPLAY.
> 
> Correct, but would there be any harm in reordering the patches?  Before this
> patch DPU_CTL_SPLIT_DISPLAY seems to have caused wrongfully allocating multiple
> CTLs when multiple intfs are requested anyway.

Why do you think that it is done wrongly? Before this patch there was no
way to use one CTL in such a case.

> 
> - Marijn
> 
> > > Other than that, this is all successfully tested and:
> > > 
> > > Reviewed-by: Marijn Suijten <marijn.suijten@...ainline.org>
> > > 
> > > >  			continue;
> > > >  
> > > >  		ctl_idx[i] = j;
> > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> > > > index 99bd594ee0d1995eca5a1f661b15e24fdf6acf39..130f753c36338544e84a305b266c3b47fa028d84 100644
> > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> > > > @@ -24,6 +24,7 @@ struct dpu_global_state;
> > > >   * @dspp_blks: array of dspp hardware resources
> > > >   * @hw_sspp: array of sspp hardware resources
> > > >   * @cdm_blk: cdm hardware resource
> > > > + * @has_legacy_ctls: DPU uses pre-ACTIVE CTL blocks.
> > > >   */
> > > >  struct dpu_rm {
> > > >  	struct dpu_hw_blk *pingpong_blks[PINGPONG_MAX - PINGPONG_0];
> > > > @@ -37,6 +38,7 @@ struct dpu_rm {
> > > >  	struct dpu_hw_blk *dsc_blks[DSC_MAX - DSC_0];
> > > >  	struct dpu_hw_sspp *hw_sspp[SSPP_MAX - SSPP_NONE];
> > > >  	struct dpu_hw_blk *cdm_blk;
> > > > +	bool has_legacy_ctls;
> > > >  };
> > > >  
> > > >  struct dpu_rm_sspp_requirements {
> > > > 
> > > > -- 
> > > > 2.39.5
> > > > 
> > 
> > -- 
> > With best wishes
> > Dmitry

-- 
With best wishes
Dmitry