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    SubjectRe: [PATCH 5.4 026/109] drm/sun4i: mixer: Call of_dma_configure if theres an IOMMU
    Hi Greg,

    On Wed, Jul 15, 2020 at 3:11 AM Greg Kroah-Hartman
    <gregkh@linuxfoundation.org> wrote:
    >
    > From: Maxime Ripard <maxime@cerno.tech>
    >
    > [ Upstream commit 842ec61f4006a6477a9deaedd69131e9f46e4cb5 ]
    >
    > The main DRM device is actually a virtual device so it doesn't have the
    > iommus property, which is instead on the DMA masters, in this case the
    > mixers.

    The iommu driver and DT changes were added in v5.8-rc1. IMO There is no
    point in backporting this patch to any stable kernel.

    ChenYu

    > Add a call to of_dma_configure with the mixers DT node but on the DRM
    > virtual device to configure it in the same way than the mixers.
    >
    > Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
    > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
    > Link: https://patchwork.freedesktop.org/patch/msgid/9a4daf438dd3f2fe07afb23688bfb793a0613d7d.1589378833.git-series.maxime@cerno.tech
    > (cherry picked from commit b718102dbdfd0285ad559687a30e27cc9124e592)
    > [Maxime: Applied to -fixes since it missed the merge window and display is
    > broken without it]
    > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
    > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > ---
    > drivers/gpu/drm/sun4i/sun8i_mixer.c | 13 +++++++++++++
    > 1 file changed, 13 insertions(+)
    >
    > diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c b/drivers/gpu/drm/sun4i/sun8i_mixer.c
    > index 18b4881f44814..e24f225d80f1f 100644
    > --- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
    > +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
    > @@ -452,6 +452,19 @@ static int sun8i_mixer_bind(struct device *dev, struct device *master,
    > mixer->engine.ops = &sun8i_engine_ops;
    > mixer->engine.node = dev->of_node;
    >
    > + if (of_find_property(dev->of_node, "iommus", NULL)) {
    > + /*
    > + * This assume we have the same DMA constraints for
    > + * all our the mixers in our pipeline. This sounds
    > + * bad, but it has always been the case for us, and
    > + * DRM doesn't do per-device allocation either, so we
    > + * would need to fix DRM first...
    > + */
    > + ret = of_dma_configure(drm->dev, dev->of_node, true);
    > + if (ret)
    > + return ret;
    > + }
    > +
    > /*
    > * While this function can fail, we shouldn't do anything
    > * if this happens. Some early DE2 DT entries don't provide
    > --
    > 2.25.1
    >
    >
    >

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