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 17:59:13 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...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

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


>
> > +      */
> > +     if (p->wide_bus_en && !dp_intf)
> > +             data_width = p->width >> 1;
> > +
> >       hsync_data_start_x = hsync_start_x;
> >       hsync_data_end_x =  hsync_start_x + data_width - 1;
> >
> >
> > --
> > 2.34.1
> >
>
> --
> With best wishes
> Dmitry