linux-kernel - Re: [PATCH v2] drm/amd/display: Add pixel encoding info to debugfs

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Date: Tue, 21 May 2024 22:06:21 +0200
From: Rino André Johnsen <rinoandrejohnsen@...il.com>
To: Christian König <christian.koenig@....com>
Cc: alexander.deucher@....com, Harry Wentland <harry.wentland@....com>, 
	Leo Li <sunpeng.li@....com>, Rodrigo Siqueira <Rodrigo.Siqueira@....com>, 
	"Pan, Xinhui" <Xinhui.Pan@....com>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Aurabindo Pillai <aurabindo.pillai@....com>, Hersen Wu <hersenxs.wu@....com>, 
	Hamza Mahfooz <hamza.mahfooz@....com>, Wayne Lin <wayne.lin@....com>, 
	Srinivasan Shanmugam <srinivasan.shanmugam@....com>, Fangzhi Zuo <jerry.zuo@....com>, 
	Tom Chung <chiahsuan.chung@....com>, Mario Limonciello <mario.limonciello@....com>, 
	Nicholas Kazlauskas <nicholas.kazlauskas@....com>, amd-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/amd/display: Add pixel encoding info to debugfs

What is already there in debugfs is 'bpc' and 'colorspace', but not
the pixel encoding/format.
I have searched high and low for that to be able to verify that my
monitor and computer are using my preferred combination of all those
three values.

I do think it should be available as a standard DRM CRTC property, but
for the time being, I figured that a simple debugfs property would be
sufficient for time being.

Rino


On Tue, May 21, 2024 at 9:04 PM Christian König
<christian.koenig@....com> wrote:
>
> Am 21.05.24 um 07:11 schrieb Rino Andre Johnsen:
> > [Why]
> > For debugging and testing purposes.
> >
> > [How]
> > Create amdgpu_current_pixelencoding debugfs entry.
> > Usage: cat /sys/kernel/debug/dri/1/crtc-0/amdgpu_current_pixelencoding
>
> Why isn't that available as standard DRM CRTC property in either sysfs
> or debugfs?
>
> I think the format specifiers should already be available somewhere there.
>
> Regards,
> Christian.
>
> >
> > Signed-off-by: Rino Andre Johnsen <rinoandrejohnsen@...il.com>
> > ---
> >
> > Changes in v2:
> > 1. Do not initialize dm_crtc_state to NULL.
> > ---
> >   .../amd/display/amdgpu_dm/amdgpu_dm_debugfs.c | 47 +++++++++++++++++++
> >   1 file changed, 47 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> > index 27d5c6077630..4254d4a4b56b 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
> > @@ -1160,6 +1160,51 @@ static int amdgpu_current_colorspace_show(struct seq_file *m, void *data)
> >   }
> >   DEFINE_SHOW_ATTRIBUTE(amdgpu_current_colorspace);
> >
> > +/*
> > + * Returns the current pixelencoding for the crtc.
> > + * Example usage: cat /sys/kernel/debug/dri/0/crtc-0/amdgpu_current_pixelencoding
> > + */
> > +static int amdgpu_current_pixelencoding_show(struct seq_file *m, void *data)
> > +{
> > +     struct drm_crtc *crtc = m->private;
> > +     struct drm_device *dev = crtc->dev;
> > +     struct dm_crtc_state *dm_crtc_state;
> > +     int res = -ENODEV;
> > +
> > +     mutex_lock(&dev->mode_config.mutex);
> > +     drm_modeset_lock(&crtc->mutex, NULL);
> > +     if (crtc->state == NULL)
> > +             goto unlock;
> > +
> > +     dm_crtc_state = to_dm_crtc_state(crtc->state);
> > +     if (dm_crtc_state->stream == NULL)
> > +             goto unlock;
> > +
> > +     switch (dm_crtc_state->stream->timing.pixel_encoding) {
> > +     case PIXEL_ENCODING_RGB:
> > +             seq_puts(m, "RGB");
> > +             break;
> > +     case PIXEL_ENCODING_YCBCR422:
> > +             seq_puts(m, "YCBCR422");
> > +             break;
> > +     case PIXEL_ENCODING_YCBCR444:
> > +             seq_puts(m, "YCBCR444");
> > +             break;
> > +     case PIXEL_ENCODING_YCBCR420:
> > +             seq_puts(m, "YCBCR420");
> > +             break;
> > +     default:
> > +             goto unlock;
> > +     }
> > +     res = 0;
> > +
> > +unlock:
> > +     drm_modeset_unlock(&crtc->mutex);
> > +     mutex_unlock(&dev->mode_config.mutex);
> > +
> > +     return res;
> > +}
> > +DEFINE_SHOW_ATTRIBUTE(amdgpu_current_pixelencoding);
> >
> >   /*
> >    * Example usage:
> > @@ -3688,6 +3733,8 @@ void crtc_debugfs_init(struct drm_crtc *crtc)
> >                           crtc, &amdgpu_current_bpc_fops);
> >       debugfs_create_file("amdgpu_current_colorspace", 0644, crtc->debugfs_entry,
> >                           crtc, &amdgpu_current_colorspace_fops);
> > +     debugfs_create_file("amdgpu_current_pixelencoding", 0644, crtc->debugfs_entry,
> > +                         crtc, &amdgpu_current_pixelencoding_fops);
> >   }
> >
> >   /*
>