linux-kernel - Re: [Freedreno] [PATCH] drm/msm/dpu: Remove chatty vbif debug print

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Message-ID: <CAF6AEGsDyvFVxAME1_VUprPKdrpEGdvP9XrQEG_-=1mRRcRBow@mail.gmail.com>
Date:   Wed, 18 Nov 2020 07:49:31 -0800
From:   Rob Clark <robdclark@...il.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Abhinav Kumar <abhinavk@...eaurora.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Sean Paul <sean@...rly.run>,
        Kalyan Thota <kalyan_t@...eaurora.org>
Subject: Re: [Freedreno] [PATCH] drm/msm/dpu: Remove chatty vbif debug print

On Tue, Nov 17, 2020 at 2:53 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting abhinavk@...eaurora.org (2020-11-17 12:34:56)
> > On 2020-11-17 09:26, Stephen Boyd wrote:
> > > I don't know what this debug print is for but it is super chatty,
> > > throwing 8 lines of debug prints in the logs every time we update a
> > > plane. It looks like it has no value. Let's nuke it so we can get
> > > better logs.
> > >
> > > Cc: Sean Paul <sean@...rly.run>
> > > Cc: Abhinav Kumar <abhinavk@...eaurora.org>
> > > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> >
> > > ---
> > >  drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c | 3 ---
> > >  1 file changed, 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c
> > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c
> > > index 5e8c3f3e6625..5eb2b2ee09f5 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_vbif.c
> > > @@ -245,9 +245,6 @@ void dpu_vbif_set_qos_remap(struct dpu_kms
> > > *dpu_kms,
> > >       forced_on = mdp->ops.setup_clk_force_ctrl(mdp, params->clk_ctrl,
> > > true);
> > >
> > >       for (i = 0; i < qos_tbl->npriority_lvl; i++) {
> > > -             DPU_DEBUG("vbif:%d xin:%d lvl:%d/%d\n",
> > > -                             params->vbif_idx, params->xin_id, i,
> > > -                             qos_tbl->priority_lvl[i]);
> >
> > Instead of getting rid of this print, we should optimize the caller of
> > this.
>
> Does the print tell us anything? Right now it prints 8 lines where it
> feels like it could be trimmed down:
>
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:0/3
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:1/3
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:2/4
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:3/4
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:4/5
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:5/5
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:6/6
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 lvl:7/6
>
> maybe one line that combines the index into values?
>
>            [drm:dpu_vbif_set_qos_remap] vbif:0 xin:0 [3 3 4 4 5 5 6 6]
>

or possibly convert to a tracepoint (so it doesn't spam the drm_trace buffer)

BR,
-R

> But again I have no idea if this print is really useful. Maybe we can
> print it only if the value changes from what was already there?
> Basically move the print into dpu_hw_set_qos_remap() and then skip out
> early if nothing changed or print and modify the register.
>
> > This is what
> > we are doing in downstream. So we need to update the property only if we
> > are switching from a RT client
> > to non-RT client for the plane and vice-versa. So we should try to do
> > the same thing here.
> >
> >         is_rt = sde_crtc_is_rt_client(crtc, crtc->state);
> >         if (is_rt != psde->is_rt_pipe) {
> >                 psde->is_rt_pipe = is_rt;
> >                 pstate->dirty |= SDE_PLANE_DIRTY_QOS;
> >         }
> >
> >
> >         if (pstate->dirty & DPU_PLANE_DIRTY_QOS)
> >                 _dpu_plane_set_qos_remap(plane);
> >
>
> Sounds great! Can you send the patch?