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

[Christophe Branchereau]

Hello, fixes the hdmi glitches for me on jz4770.

Tested-by: Christophe Branchereau <cbranchereau at gmail.com>

On Sun, Jul 3, 2022 at 8:43 AM Sam Ravnborg <sam at ravnborg.org> wrote:

> 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 at vger.kernel.org>
> > Fixes: 90b86fcc47b4 ("DRM: Add KMS driver for the Ingenic JZ47xx SoCs")
> > Signed-off-by: Paul Cercueil <paul at crapouillou.net>
> Acked-by: Sam Ravnborg <sam at ravnborg.org>
>
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