Re: [PATCH] drm/ingenic: Use the highest possible DMA burst size

Sam Ravnborg
2022-07-03T06:43:46Z

Hi Paul,

On Sun, Jul 03, 2022 at 12:07:27AM +0100, Paul Cercueil wrote:
> Until now, when running at the maximum resolution of 1280x720 at 32bpp
> on the JZ4770 SoC the output was garbled, the X/Y position of the
> top-left corner of the framebuffer warping to a random position with
> the whole image being offset accordingly, every time a new frame was
> being submitted.
>
> This problem can be eliminated by using a bigger burst size for the DMA.

Are there any alignment constraints of the framebuffer that depends on
the burst size? I am hit by this with some atmel IP - which is why I
ask.

Patch looks good and is a-b.

>
> Set in each soc_info structure the maximum burst size supported by the
> corresponding SoC, and use it in the driver.
>
> Set the new value using regmap_update_bits() instead of
> regmap_set_bits(), since we do want to override the old value of the
> burst size. (Note that regmap_set_bits() wasn't really valid before for
> the same reason, but it never seemed to be a problem).
>
> Cc: <stable@vger.kernel.org>
> Fixes: 90b86fcc47b4 ("DRM: Add KMS driver for the Ingenic JZ47xx SoCs")
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Sam Ravnborg <sam@ravnborg.org>