linux-kernel - Re: [PATCH v3 05/15] drm/msm/dpu: fix mixer number counter on allocation

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Message-ID: <CABymUCPm-+RYVGx6aXXPqgEcg+x7vhrN_HanJvvNrFkJj6o5Aw@mail.gmail.com>
Date: Thu, 9 Jan 2025 12:40:23 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Jessica Zhang <quic_jesszhan@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 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 05/15] drm/msm/dpu: fix mixer number counter on allocation

Jessica Zhang <quic_jesszhan@...cinc.com> 于2025年1月9日周四 09:29写道：
>
>
>
> On 12/18/2024 11:49 PM, Jun Nie wrote:
> > Add the case to reserve multiple pairs mixers for high resolution.
> > Current code only supports one pair of mixer usage case. To support
> > quad-pipe usage case, two pairs of mixers are needed.
> >
> > Current code resets number of mixer on failure of pair's peer test and
> > retry on another pair. If two pairs are needed, the failure on the test
> > of 2nd pair results clearing to the 1st pair. This patch only clear the
> > bit for the 2nd pair allocation before retry on another pair.
>
> Hi Jun,
>
> I think the commit message wording is a bit unclear. Maybe something
> like "Reset the current lm_count to an even number instead of completely
> clearing it. This prevents all pairs from being cleared in cases where
> multiple LM pairs are needed"

Thanks for the suggestion! Will adopt it.
>
> >
> > Signed-off-by: Jun Nie <jun.nie@...aro.org>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > index cde3c5616f9bc..a8b01b78c02c7 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> > @@ -316,7 +316,11 @@ static int _dpu_rm_reserve_lms(struct dpu_rm *rm,
> >               if (!rm->mixer_blks[i])
> >                       continue;
> >
> > -             lm_count = 0;
> > +             /*
> > +              * Clear the last bit to drop the previous primary mixer if
> > +              * fail to find its peer.
>
> Same here can we reword it to something like "Reset lm_count to an even
> index. This will drop the previous primary mixer if ..."

Will do.

>
> > +              */
> > +             lm_count &= 0xfe;
>
> Nit: Can we directly clear the first bit instead of doing an 8-bit bitmask?

Could you elaborate on it? Or you are suggesting to mask 0xFFFFFFFE?

- Jun

>
> Thanks,
>
> Jessica Zhang
>
> >               lm_idx[lm_count] = i;
> >
> >               if (!_dpu_rm_check_lm_and_get_connected_blks(rm, global_state,
> >
> > --
> > 2.34.1
> >
>