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

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Message-ID: <666e36b7-5379-46ef-a16b-00ec499fb42c@amd.com>
Date: Wed, 22 May 2024 08:36:54 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Rino André Johnsen <rinoandrejohnsen@...il.com>,
 Simon Ser <contact@...rsion.fr>
Cc: Christian König <christian.koenig@....com>,
 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

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