[PATCH v3 11/13] drm/fb-helper: Fix single-probe color-format selection

[Linus Walleij]

On Fri, May 12, 2023 at 4:11 PM Thomas Zimmermann <tzimmermann at suse.de> wrote:

> > Any hints on how we can fix this?
>
> According to a quick grep for fb_bpp, it's only used for the call to
> drm_fbdev_dma_setup(), right? In this case, you should set it to 15 for
> the models without rgb565. The switch at [1] should then pick the
> correct values.

I tried this. It does work better, the selected format becomes

0x35315258 = LE '5', '1', 'R', 'X" = 'X', 'R', '1', '5', =
DRM_FORMAT_XRGB1555.

But the display is flickering like crazy so the updating frequency is
totally off, which is because it does not scale down the resolution,
the print used to be:

Console: switching to colour frame buffer device 80x30
drm-clcd-pl111 c1000000.display: [drm] fb0: pl111drmfb frame buffer device

It is now:

Console: switching to colour frame buffer device 100x37
drm-clcd-pl111 c1000000.display: [drm] fb0: pl111drmfb frame buffer device

100x37! (i.e. 800x296), this display can only do 640x240.
Any idea what else is going wrong here? Or is this another regression
on top of the first regression ... I was under the impression that
your change was only about formats not resolutions.

Yours,
Linus Walleij