RE: [PATCH] drm/edid: ignore the CEA modes not defined in CEA-861-D

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 01 Jun 2022, "Tseng, William" <william.tseng@intel.com> wrote:
> Thanks, Jani.
> This is the issue ticket. https://gitlab.freedesktop.org/drm/intel/-/issues/6087#note_1400843

Copy-paste fail? Does not seem right.

BR,
Jani.


PS. Also, for some reason you added this in your mail:

Reply-To: "20220531103421.11363-1-william.tseng@intel.com"
	<20220531103421.11363-1-william.tseng@intel.com>




>
>
> Regards
> William
>
> -----Original Message-----
> From: Jani Nikula <jani.nikula@linux.intel.com> 
> Sent: Tuesday, May 31, 2022 7:07 PM
> To: Tseng, William <william.tseng@intel.com>; dri-devel@lists.freedesktop.org
> Cc: Lee, Shawn C <shawn.c.lee@intel.com>; Wayne Lin <waynelin@amd.com>; Tseng, William <william.tseng@intel.com>
> Subject: Re: [PATCH] drm/edid: ignore the CEA modes not defined in CEA-861-D
>
> On Tue, 31 May 2022, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>> On Tue, 31 May 2022, William Tseng <william.tseng@intel.com> wrote:
>>> This is a workaround for HDMI 1.4 sink which has a CEA mode with 
>>> higher vic than what is defined in CEA-861-D.
>>>
>>> As an example, a HDMI 1.4 sink has the video format 2560x1080p to be 
>>> displayed and the video format is indicated by both SVD (with vic 90 
>>> and pictuure aspect ratio 64:27) and DTD.  When connecting to such 
>>> sink, source can't output the video format in SVD because an error is 
>>> returned by drm_hdmi_avi_infoframe_from_display_mode(), which can't 
>>> fill the infoframe with pictuure aspect ratio 64:27 and the vic, 
>>> which is originally 90 and is changed to 0 by drm_mode_cea_vic().
>>>
>>> To work around it, this patch ignores such CEA modes in 
>>> do_cea_modes() so the modes won't be processed in drm_hdmi_avi_infoframe_from_display_mode().
>>> And only the video format in DTD can be dispalyed.
>
> I think we should also have a bug filed on this, with the offending EDID attached for posterity.
>
> BR,
> Jani.
>
>
>>>
>>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> Cc: Wayne Lin <waynelin@amd.com>
>>> Cc: Lee Shawn C <shawn.c.lee@intel.com>
>>> Signed-off-by: William Tseng <william.tseng@intel.com>
>>> ---
>>>  drivers/gpu/drm/drm_edid.c | 39 
>>> +++++++++++++++++++++++++-------------
>>>  1 file changed, 26 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c 
>>> index bc43e1b32092..a93f68878bfd 100644
>>> --- a/drivers/gpu/drm/drm_edid.c
>>> +++ b/drivers/gpu/drm/drm_edid.c
>>> @@ -3982,6 +3982,19 @@ drm_display_mode_from_cea_vic(struct 
>>> drm_device *dev,  }  EXPORT_SYMBOL(drm_display_mode_from_cea_vic);
>>>  
>>> +static bool is_hdmi2_sink(const struct drm_connector *connector) {
>>> +	/*
>>> +	 * FIXME: sil-sii8620 doesn't have a connector around when
>>> +	 * we need one, so we have to be prepared for a NULL connector.
>>> +	 */
>>> +	if (!connector)
>>> +		return true;
>>> +
>>> +	return connector->display_info.hdmi.scdc.supported ||
>>> +		connector->display_info.color_formats & DRM_COLOR_FORMAT_YCBCR420; 
>>> +}
>>> +
>>>  static int
>>>  do_cea_modes(struct drm_connector *connector, const u8 *db, u8 len)  
>>> { @@ -3993,6 +4006,19 @@ do_cea_modes(struct drm_connector 
>>> *connector, const u8 *db, u8 len)
>>>  
>>>  		mode = drm_display_mode_from_vic_index(connector, db, len, i);
>>>  		if (mode) {
>>> +			u8 vic = svd_to_vic(db[i]);
>>> +
>>> +			if (!drm_valid_cea_vic(vic))
>>> +				continue;
>>
>> drm_display_mode_from_vic_index() returns NULL in this case.
>>
>>> +
>>> +			/*
>>> +			 * HDMI 1.4 VIC range: 1 <= VIC <= 64 (CEA-861-D) but
>>> +			 * HDMI 2.0 VIC range: 1 <= VIC <= 107 (CEA-861-F). So we
>>> +			 * have to make sure we dont break HDMI 1.4 sinks.
>>> +			 */
>>> +			if (!is_hdmi2_sink(connector) && vic > 64)
>>> +				continue;
>>
>> I'll need to double check if this is the right thing to do... but I 
>> guess the question becomes if this shouldn't be within 
>> drm_display_mode_from_vic_index().
>>
>> Duplicating the condition from drm_mode_cea_vic() is probably not a 
>> good idea.
>>
>> The continues in both above branches leak the mode.
>>
>>
>> BR,
>> Jani.
>>
>>
>>> +
>>>  			/*
>>>  			 * YCBCR420 capability block contains a bitmap which
>>>  			 * gives the index of CEA modes from CEA VDB, which @@ -5846,19 
>>> +5872,6 @@ void drm_set_preferred_mode(struct drm_connector 
>>> *connector,  }  EXPORT_SYMBOL(drm_set_preferred_mode);
>>>  
>>> -static bool is_hdmi2_sink(const struct drm_connector *connector) -{
>>> -	/*
>>> -	 * FIXME: sil-sii8620 doesn't have a connector around when
>>> -	 * we need one, so we have to be prepared for a NULL connector.
>>> -	 */
>>> -	if (!connector)
>>> -		return true;
>>> -
>>> -	return connector->display_info.hdmi.scdc.supported ||
>>> -		connector->display_info.color_formats & DRM_COLOR_FORMAT_YCBCR420;
>>> -}
>>> -
>>>  static u8 drm_mode_hdmi_vic(const struct drm_connector *connector,
>>>  			    const struct drm_display_mode *mode)  {
>
> --
> Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center