Re: [RFC PATCH] drm/sitronix: add ST7789V panel driver

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 16.02.26 um 16:38 schrieb Archit Anant:
> On Mon, Feb 16, 2026 at 1:17 PM Javier Martinez Canillas
> <javierm@redhat.com> wrote:
>
> Hi Javier,
>
>> Archit Anant <architanant5@gmail.com> writes:
>>
>> Hello Archit,
>>
>>> Hi ChenYu,
>>>
>>> Thank you for the detailed review and the pointers toward the documentation.
>>> I will ensure the headers are sorted alphabetically and the driver name
>>> conflict is resolved in the next iteration.
>>>
>>>> The reset logic in mipi_dbi is inverted when compared to panel-st7789v.
>>>> mipi_dbi needs to be taught the "proper" reset polarity.
>>> Noted. I will look into the mipi_dbi core to see how to handle the reset
>>> polarity correctly.
>>>
>>>> Instead this functionality could be merged into the existing panel-st7789v
>>>> driver. You mentioned above that that driver only supports the 9-bit SPI
>>>> transfer mode. However porting that driver over to mipi_dbi would fix this,
>>>> and remove some redundant code. And tinydrm support could be added on top
>>>> of that.
>>>>
>>>> I actually mentioned I was going to work on this on IRC. But I only ported
>>>> the driver over to use mipi_dbi, and haven't gotten around to adding
>>>> tinydrm support. I can send out the conversion patches if that helps
>>>> you.
>>> That would be fantastic and would save a lot of redundant effort. If you
>>> send out the patches to convert the existing panel-st7789v driver to
>>> mipi_dbi, I would be happy to build the 'tiny' (simple display pipe)
>>> support on top of your series.
>>>
>> I think we want to get rid of the simple display pipeline and instead just
>> use regulator atomic helpers, even for the tiny DRM drivers.
>>
>> Please take a look to previous commits such as 2037174993c8 ("drm/bochs:
>> Use regular atomic helpers") or 622113b9f11f ("drm/ssd130x: Replace simple
>> display helpers with the atomic helpers").
>>
>> --
>> Best regards,
>>
>> Javier Martinez Canillas
>> Core Platforms
>> Red Hat
>>
> Thank you for pointing this out. I based this implementation on the
> existing st7735r driver, which currently uses the simple pipe.
>
> I will study the bochs and ssd130x commits to understand the migration to
> regular atomic helpers.
>
> If the goal is to move tiny DRM drivers away from the simple pipe, updating
> the Sitronix drivers to this new pattern sounds much better.
> I will incorporate this into my plan for the next iteration
> (building on top of ChenYu's work).

The thing is that this driver builds upon mipi_dbi_dev, which uses 
simple_display_pipeline internally. So it might be legitimate to use it 
here. Otherwise all the MIPI support from drm_mipi_dbi.c would have to 
be duplicated.

Best regards
Thomas

>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)