[PATCH] drm: mxsfb: Support 24-bit SPWG, JEIDA bus formats

[Marek Vasut]

On 7/4/21 11:57 AM, Jagan Teki wrote:
> Hi Marek,
> 
> On Sun, Jul 4, 2021 at 3:23 PM Marek Vasut <marex at denx.de> wrote:
>>
>> On 7/4/21 11:38 AM, Jagan Teki wrote:
>>> 24-bit SPWG, JEIDA bus formats are considered as 24-bit
>>> bus widths for LCDC_CTRL register in mxsfb.
>>>
>>> Add support for it.
>>>
>>> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
>>> ---
>>>    drivers/gpu/drm/mxsfb/mxsfb_kms.c | 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
>>> index 22cb749fc9bc..5657155f9633 100644
>>> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
>>> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
>>> @@ -85,6 +85,8 @@ static void mxsfb_set_formats(struct mxsfb_drm_private *mxsfb,
>>>                ctrl |= CTRL_BUS_WIDTH_18;
>>>                break;
>>>        case MEDIA_BUS_FMT_RGB888_1X24:
>>> +     case MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA:
>>> +     case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
>>
>> On MX8MM/MN, the bus between LCDIF and DSIM is plain parallel bus, so
>> this patch is wrong.
> 
> Unsure since these flags are setting from panel side.

On MX8MM/MN, the panel is NOT connected directly to the LCDIF. There is
LCDIF->(DPI bus)->DSIM bridge->(DSI bus)->DSI-to-LVDS-bridge->(LVDS 
bus)->LVDS panel
It is the DSI bus past DSIM that is coming out of the SoC.

>> You want to pick
>> drm: mxsfb: Use bus_format from the nearest bridge if present
>> and then implement .atomic_get_input_bus_fmts on all your bridges. And
>> only then you will get the correct MEDIA_BUS_FMT_RGB888_1X24 here.
> 
> I did pick this patch along with all your mxsfb recent changes, but
> issue still persist. It work only when I set the LCDC_CTRL explicitly
> like the patch does.

You must implement .atomic_get_input_bus_fmts on all your bridges .
Then the format gets propagated correctly.

Look at e.g.
drm/bridge: ti-sn65dsi83: Replace connector format patching with 
atomic_get_input_bus_fmts
same thing applies to the DSIM, and possibly whatever other bridge you 
might have in the LCDIF->...->LVDS panel path.