[PATCH 5/6] drm/mediatek: Convert to use CMA helpers

Rob Herring robh at kernel.org
Wed Oct 23 17:42:43 UTC 2019

On Tue, Oct 22, 2019 at 12:07 PM Matthias Brugger
<matthias.bgg at gmail.com> wrote:
> Hi Rob,
> On 21/10/2019 23:45, Rob Herring wrote:
> > The only reason the Mediatek driver doesn't use the CMA helpers is it
> > sets DMA_ATTR_NO_KERNEL_MAPPING and does a vmap() on demand. Using
> > vmap() is not even guaranteed to work as DMA buffers may not have a
> > struct page. Now that the CMA helpers support setting
> > DMA_ATTR_NO_KERNEL_MAPPING as needed or not, convert Mediatek driver to
> > use CMA helpers.
> >
> > Cc: CK Hu <ck.hu at mediatek.com>
> > Cc: Philipp Zabel <p.zabel at pengutronix.de>
> > Cc: David Airlie <airlied at linux.ie>
> > Cc: Daniel Vetter <daniel at ffwll.ch>
> > Cc: Matthias Brugger <matthias.bgg at gmail.com>
> > Cc: linux-arm-kernel at lists.infradead.org
> > Cc: linux-mediatek at lists.infradead.org
> > Signed-off-by: Rob Herring <robh at kernel.org>
> > ---
> I tested this on my Chromebook with some patches on top of v5.4-rc1 [1], which
> work. If I add your patches on top of that, the system does not boot up.
> Unfortunately I don't have a serial console, so I wasn't able to see if there is
> any error message.

Thanks for testing. I'm based on drm-misc-next, but don't see anything
obvious there that would matter. There are some mmap changes, but I
think they shouldn't matter.

Did you have fbcon enabled? That may give more clues about where the problem is.


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