linux-kernel - Re: [PATCH] drm/vgem: fix cache synchronization on arm/arm64

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Date:   Thu, 1 Aug 2019 08:18:45 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     David Airlie <airlied@...ux.ie>,
        Deepak Sharma <deepak.sharma@....com>,
        Emil Velikov <emil.velikov@...labora.com>,
        Eric Anholt <eric@...olt.net>,
        Eric Biggers <ebiggers@...gle.com>,
        Imre Deak <imre.deak@...el.com>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/vgem: fix cache synchronization on arm/arm64

On Thu, Aug 1, 2019 at 5:40 AM Chris Wilson <chris@...is-wilson.co.uk> wrote:
>
> Quoting Sean Paul (2019-07-31 20:23:31)
> > On Fri, Jul 19, 2019 at 11:21:53AM +0200, Daniel Vetter wrote:
> > > On Wed, Jul 17, 2019 at 02:15:37PM -0700, Rob Clark wrote:
> > > > From: Rob Clark <robdclark@...omium.org>
> > > >
> > > > drm_cflush_pages() is no-op on arm/arm64.  But instead we can use
> > > > dma_sync API.
> > > >
> > > > Fixes failures w/ vgem_test.
> > > >
> > > > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > > > ---
> > > > An alternative approach to the series[1] I sent yesterday
> > > >
> > > > On the plus side, it keeps the WC buffers and avoids any drm core
> > > > changes.  On the minus side, I don't think it will work (at least
> > > > on arm64) prior to v5.0[2], so the fix can't be backported very
> > > > far.
> > >
> > > Yeah seems a lot more reasonable.
> > >
> > > Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>
> >
> > Applied to drm-misc-fixes, thanks!
>
> But it didn't actually fix the failures in CI.

Hmm, that is unfortunate, I'd assumed that silence meant latest
version was working in CI..

dma_sync_sg_* doesn't work on x86?  It would be kinda unfortunate to
have vgem only work on x86 *or* arm..  maybe bringing back
drm_cflush_pages() could make it work in both cases

BR,
-R