Re: [PATCH] drm: bridge: fsl-ldb: fixup mode on freq mismatch

[Nikolaus Voss <nv@vosn.de>]

Hi Marek,

On 09.12.2024 22:46, Marek Vasut wrote:
> On 12/9/24 9:46 AM, Nikolaus Voss wrote:
>>>>>> and store the panel's timing in EDID EEPROM.
>>>>> Oh, that is a new one. Does the EDID EEPROM store the entirety of
>>>>> 'struct display_timing {}' somehow , or is that a custom format ?
>>>> 
>>>> Well, sort of ;-). VESA has taken care of this 30 years ago
>>>> (https://en.wikipedia.org/wiki/Extended_Display_Identification_Data).
>>>> 
>>>> DRM handles this with drm_get_edid() and siblings, e.g. :
>>> 
>>> EDID can not encode all the information in struct display_timing {} ,
>>> or can it ?
>>> 
>>> I think what you would be missing are bus_flags , bus_format and
>>> possibly the single/dual link and channel (odd/even) mapping, won't
>>> you ?
>> 
>> Yes, that's right. I use the vendor block for bus_flags and bus_format
>> now, but that's not standard and not portable of course.
>> 
>> My first idea was to store the DT overlay in the display EEPROM but
>> a standard 1k EEPROM is too small for that.
> Understood. I had the same problem, in the end I went for custom
> encoding in the EEPROM but the amount of panels was limited in my
> case.
> 
> Indeed, DTO does not fit the EEPROM and EDID is not really fitting too
> well to DPI/LVDS panels, it has too many fields that are specific to
> regular pluggable panels and not useful on DPI/LVDS ones.

The curse of backward-compatibility ;-). Nevertheless, we are doing well
with EDID for years now. 95% is implemented in standard kernel, you just
need a few quirks.

-- 
Nikolaus Voss