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

[Mario Limonciello]

+ Simon

On 5/22/2024 05:07, Rino André Johnsen wrote:
> To be perfectly honest with you, I haven't given that much though. I
> used the 'bpc' and 'colorspace' property in debugfs, since I could not
> find that information anywhere else. And since I also needed to verify
> the pixel encoding being used, I added it where those other values
> were. That made for a simple and easy addition for this property.
>
> If you want me to do this differently, let me know. And please point
> me to the standardized DRM property where I should expose the values.

Here's a pointer to where the colorspace property is created:

https://github.com/torvalds/linux/blob/v6.9/drivers/gpu/drm/drm_connector.c#L2147

I would expect you can make another property for the information you're 
looking for and then can get it from userspace using standard property
APIs.

> Rino
>
> On Tue, May 21, 2024 at 10:55 PM Mario Limonciello
> <mario.limonciello@xxxxxxx> wrote:
> > On 5/21/2024 15:06, Rino André Johnsen wrote:
> > > 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.
> >
> > It's just about as much work either way to populate it though, why do it
> > twice instead of just doing it right the first time?
> >
> > > Rino
> > >
> > >
> > > On Tue, May 21, 2024 at 9:04 PM Christian König
> > > <christian.koenig@xxxxxxx> 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@xxxxxxxxx>
> > > > > ---
> > > > >
> > > > > 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);
> > > > >     }
> > > > >
> > > > >     /*