[PATCH] drm/fbdev-dma: Only install deferred I/O if necessary

[Linus Walleij]

Hi Thomas,

quick response as always! :)

On Wed, Sep 4, 2024 at 11:31 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:

> Deferred I/O requires struct page for framebuffer memory, which is
> not guaranteed for all DMA ranges. We thus only install deferred I/O
> if we have a framebuffer that requires it.
>
> A reported bug affected the ipu-v3 and pl111 drivers, which have video
> memory in either Normal or HighMem zones
>
> [    0.000000] Zone ranges:
> [    0.000000]   Normal   [mem 0x0000000010000000-0x000000003fffffff]
> [    0.000000]   HighMem  [mem 0x0000000040000000-0x000000004fffffff]
>
> where deferred I/O only works correctly with HighMem. See the Closes
> tags for bug reports.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Fixes: 808a40b69468 ("drm/fbdev-dma: Implement damage handling and deferred I/O")
> Reported-by: Alexander Stein <alexander.stein at ew.tq-group.com>
> Closes: https://lore.kernel.org/all/23636953.6Emhk5qWAg@steina-w/
> Reported-by: Linus Walleij <linus.walleij at linaro.org>
> Closes: https://lore.kernel.org/dri-devel/CACRpkdb+hb9AGavbWpY-=uQQ0apY9en_tWJioPKf_fAbXMP4Hg@mail.gmail.com/
> Tested-by: Alexander Stein <alexander.stein at ew.tq-group.com>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Javier Martinez Canillas <javierm at redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>

It works like a charm and LGTM.
Tested-by: Linus Walleij <linus.walleij at linaro.org>
Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij