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

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Date: Tue, 21 May 2024 15:55:34 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Rino André Johnsen <rinoandrejohnsen@...il.com>,
 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>,
 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

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@....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);
>>>    }
>>>
>>>    /*
>>