linux-kernel - Re: [PATCH v5 2/6] drm/msm/dpu: adjust data width for widen bus case

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Date: Tue, 28 May 2024 14:56:42 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jun Nie <jun.nie@...aro.org>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Vinod Koul <vkoul@...nel.org>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/6] drm/msm/dpu: adjust data width for widen bus case

On Tue, May 28, 2024 at 05:59:13PM +0800, Jun Nie wrote:
> Dmitry Baryshkov <dmitry.baryshkov@...aro.org> 于2024年5月28日周二 08:48写道：
> >
> > On Mon, May 27, 2024 at 10:21:48PM +0800, Jun Nie wrote:
> > > data is valid for only half the active window if widebus
> > > is enabled
> > >
> > > Signed-off-by: Jun Nie <jun.nie@...aro.org>
> > > ---
> > >  drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> > > index 225c1c7768ff..f97221423249 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
> > > @@ -168,6 +168,15 @@ static void dpu_hw_intf_setup_timing_engine(struct dpu_hw_intf *intf,
> > >
> > >       data_width = p->width;
> > >
> > > +     /*
> > > +      * If widebus is enabled, data is valid for only half the active window
> > > +      * since the data rate is doubled in this mode. But for the compression
> > > +      * mode in DP case, the p->width is already adjusted in
> > > +      * drm_mode_to_intf_timing_params()
> >
> > Is there any reason for divergence here?
> 
> Lots of parameters in dpu_hw_intf_setup_timing_engine() is calculated
> from timing->width,
> such as hsync_period and display_v_start. So the width cannot be
> adjusted beforehand in
> drm_mode_to_intf_timing_params(). Otherwise, we get below error.
> 
> I guess the interface timing configuration differ in silicon, thus the
> software shall handle the
> difference. If we adjust the width beforehand for DSI, we get below error.
> 
> [    6.625446] [drm:dpu_encoder_frame_done_timeout:2469] [dpu
> error]enc31 frame done timeout
> [    6.642369] [drm:dpu_encoder_phys_vid_wait_for_commit_done:525]
> [dpu error]vblank timeout: 4200c1
> [    6.642395] [drm:dpu_kms_wait_for_commit_done:493] [dpu error]wait
> for commit done returned -110
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>


-- 
With best wishes
Dmitry