linux-kernel - Re: [PATCH] drm/msm/dp: Make it possible to enable the test pattern

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Date:   Mon, 28 Jun 2021 19:55:27 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     abhinavk@...eaurora.org
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dp: Make it possible to enable the test pattern

On Mon 28 Jun 19:31 CDT 2021, abhinavk@...eaurora.org wrote:

> Hi Bjorn
> 
> On 2021-06-28 17:22, Bjorn Andersson wrote:
> > The debugfs interface contains the knobs to make the DisplayPort
> > controller output a test pattern, unfortunately there's nothing
> > currently that actually enables the defined test pattern.
> > 
> > Fixes: de3ee25473ba ("drm/msm/dp: add debugfs nodes for video pattern
> > tests")
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> 
> This is not how this debugfs node works. This is meant to be used while
> running
> DP compliance video pattern test.
> 
> https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/blob/master/tools/msm_dp_compliance.c
> 
> While the compliance test is being run with this msm_dp_compliance app
> running,
> it will draw the test pattern when it gets the "test_active" from the
> driver.
> 
> The test pattern which this app draws is as per the requirements of the
> compliance test
> as the test equipment will match the CRC of the pattern which is drawn.
> 
> The API dp_panel_tpg_config() which you are trying to call here draws the DP
> test pattern
> from the DP controller hardware but not the pattern which the compliance
> test expects.
> 

So clearly not an oversight, but rather me not understanding how to use
the test pattern.

You say that I should run msm_dp_compliance while the test is running,
so how do I run the test?

> Its just a debug API to call when required during bringup/debug purposes.
> 

Yes, I was trying to isolate the DP code from some misconfiguration in
the DPU during bringup and with this fix the debugfs interface became
useful.

Regards,
Bjorn

> Hence this is not the place to call it as it will end up breaking CTS.
> 
> Thanks
> 
> Abhinav
> 
> > ---
> >  drivers/gpu/drm/msm/dp/dp_debug.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/msm/dp/dp_debug.c
> > b/drivers/gpu/drm/msm/dp/dp_debug.c
> > index 2f6247e80e9d..82911af44905 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_debug.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_debug.c
> > @@ -305,6 +305,8 @@ static ssize_t dp_test_active_write(struct file
> > *file,
> >  				debug->panel->video_test = true;
> >  			else
> >  				debug->panel->video_test = false;
> > +
> > +			dp_panel_tpg_config(debug->panel, debug->panel->video_test);
> >  		}
> >  	}
> >  	drm_connector_list_iter_end(&conn_iter);