linux-kernel - Re: [PATCH v3 04/15] drm/msm/dpu: decide right side per last bit

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Message-ID: <CABymUCOGzvR0utNUR3-6bFDi3c3yRTUu=CcTo2-eTKBvpoU-PA@mail.gmail.com>
Date: Thu, 9 Jan 2025 12:35:48 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Jessica Zhang <quic_jesszhan@...cinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 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>, 
	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 v3 04/15] drm/msm/dpu: decide right side per last bit

Jessica Zhang <quic_jesszhan@...cinc.com> 于2025年1月9日周四 07:41写道：
>
>
>
> On 12/19/2024 2:09 PM, Dmitry Baryshkov wrote:
> > On Thu, Dec 19, 2024 at 03:49:22PM +0800, Jun Nie wrote:
> >> decide right side of a pair per last bit, in case of multiple
> >> mixer pairs.
> >
> > Proper English sentences, please. Also describe why, not what.
>
> Hi Jun,
>
> Can we also add a note in the commit message on why the last bit check
> works?

Sure. How about this?

    Currently we only support one pair of mixer, so counter's
    non-zero value is enough to mark the right one. There will
    be case with multiple mixer pairs, so let's use the last bit to
    mark the right mixer in a mixer pair. If the last bit is set, it
    marks the right mixer in the pair, it's left mixer otherwise.

>
> Thanks,
>
> Jessica Zhang
>
> >
> >>
> >> Signed-off-by: Jun Nie <jun.nie@...aro.org>
> >> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> >> ---
> >>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 5 ++---
> >>   1 file changed, 2 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> >> index 7191b1a6d41b3..41c9d3e3e3c7c 100644
> >> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> >> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> >> @@ -369,11 +369,10 @@ static void _dpu_crtc_setup_blend_cfg(struct dpu_crtc_mixer *mixer,
> >>   static void _dpu_crtc_program_lm_output_roi(struct drm_crtc *crtc)
> >>   {
> >>      struct dpu_crtc_state *crtc_state;
> >> -    int lm_idx, lm_horiz_position;
> >> +    int lm_idx;
> >>
> >>      crtc_state = to_dpu_crtc_state(crtc->state);
> >>
> >> -    lm_horiz_position = 0;
> >>      for (lm_idx = 0; lm_idx < crtc_state->num_mixers; lm_idx++) {
> >>              const struct drm_rect *lm_roi = &crtc_state->lm_bounds[lm_idx];
> >>              struct dpu_hw_mixer *hw_lm = crtc_state->mixers[lm_idx].hw_lm;
> >> @@ -384,7 +383,7 @@ static void _dpu_crtc_program_lm_output_roi(struct drm_crtc *crtc)
> >>
> >>              cfg.out_width = drm_rect_width(lm_roi);
> >>              cfg.out_height = drm_rect_height(lm_roi);
> >> -            cfg.right_mixer = lm_horiz_position++;
> >> +            cfg.right_mixer = lm_idx & 0x1;
> >>              cfg.flags = 0;
> >>              hw_lm->ops.setup_mixer_out(hw_lm, &cfg);
> >>      }
> >>
> >> --
> >> 2.34.1
> >>
> >
> > --
> > With best wishes
> > Dmitry
>