linux-kernel - Re: [PATCH v2 4/4] drm/msm/a6xx: Use the DMA API for GMU memory objects

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Message-ID: <CAF6AEGtYvjgoYxsxyu2-juuTsp9mBJUdRRUWAT3doLtpju4UmQ@mail.gmail.com>
Date:   Tue, 25 Feb 2020 16:59:02 -0800
From:   Rob Clark <robdclark@...il.com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Jordan Crouse <jcrouse@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Sharat Masetty <smasetty@...eaurora.org>,
        Sean Paul <sean@...rly.run>,
        Stephen Boyd <swboyd@...omium.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Douglas Anderson <dianders@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Daniel Vetter <daniel@...ll.ch>, Todd Kjos <tkjos@...gle.com>
Subject: Re: [PATCH v2 4/4] drm/msm/a6xx: Use the DMA API for GMU memory objects

On Tue, Feb 25, 2020 at 3:54 PM John Stultz <john.stultz@...aro.org> wrote:
>
> On Thu, Feb 20, 2020 at 10:27 AM Jordan Crouse <jcrouse@...eaurora.org> wrote:
> >
> > The GMU has very few memory allocations and uses a flat memory space so
> > there is no good reason to go out of our way to bypass the DMA APIs which
> > were basically designed for this exact scenario.
> >
> > v2: Pass force_dma false to of_dma_configure to require that the DMA
> > region be set up and return error from of_dma_configure to fail probe.
> >
> > Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> > ---
> >
> >  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 112 +++-------------------------------
> >  drivers/gpu/drm/msm/adreno/a6xx_gmu.h |   5 +-
> >  2 files changed, 11 insertions(+), 106 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > index 983afea..c36b38b 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> ...
> > -       count = bo->size >> PAGE_SHIFT;
> > +       bo->virt = dma_alloc_attrs(gmu->dev, bo->size, &bo->iova, GFP_KERNEL,
> > +               bo->attrs);
> >
> ...
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> > index 2af91ed..31bd1987 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> > @@ -13,7 +13,7 @@ struct a6xx_gmu_bo {
> >         void *virt;
> >         size_t size;
> >         u64 iova;
> > -       struct page **pages;
> > +       unsigned long attrs;
> >  };
>
> As a head up, Todd reported that this patch is causing build trouble
> w/ arm32, as the iova needs to be a dma_attr_t.
>
> I've got a patch for the android-mainline tree to fix this, but you
> might want to spin a v3 to address this.
>   https://android-review.googlesource.com/c/kernel/common/+/1243928
>

I guess based on robher's comments on the bindings, there will be a v3..

BR,
-R