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

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Message-ID: <b3456d3e4376ae1e9776f03e14513a35@codeaurora.org>
Date:   Mon, 28 Jun 2021 17:31:39 -0700
From:   abhinavk@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.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

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.

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

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);