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

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Message-ID: <4c955afcc2eb28794a5bbcc0e1642592@codeaurora.org>
Date:   Wed, 18 Nov 2020 12:03:51 -0800
From:   abhinavk@...eaurora.org
To:     Rob Clark <robdclark@...il.com>
Cc:     Stephen Boyd <swboyd@...omium.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

Hi Stephen

On 2020-11-18 07:49, Rob Clark wrote:
> 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?

Will finalize approach and send the patch in a day or two.

Thanks

Abhinav