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From:   Paul Burton <paul.burton@mips.com>
To:     Serge Semin <fancer.lancer@gmail.com>
CC:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Christian Koenig <christian.koenig@amd.com>,
        Huang Rui <ray.huang@amd.com>,
        Junwei Zhang <Jerry.Zhang@amd.com>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        James Hogan <jhogan@kernel.org>,
        "Vadim V . Vlasov" <vadim.vlasov@t-platforms.ru>
Subject: Re: [PATCH] drm: Permit video-buffers writecombine mapping for MIPS
Thread-Topic: [PATCH] drm: Permit video-buffers writecombine mapping for MIPS
Thread-Index: AQHU+dCYLc0FOHZW+USx3qmHwO4wf6ZKBuCA
Date:   Tue, 23 Apr 2019 17:52:06 +0000
Message-ID: <20190423175201.z7qfs2r5znx6uq5t@pburton-laptop>
References: <20190423123122.32573-1-fancer.lancer@gmail.com>
In-Reply-To: <20190423123122.32573-1-fancer.lancer@gmail.com>
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Hi Serge,

On Tue, Apr 23, 2019 at 03:31:22PM +0300, Serge Semin wrote:
> Since commit 4b050ba7a66c ("MIPS: pgtable.h: Implement the
> pgprot_writecombine function for MIPS") and commit c4687b15a848 ("MIPS: F=
ix
> definition of pgprot_writecombine()") write-combine vma mapping is
> available to be used by kernel subsystems for MIPS. In particular the
> uncached accelerated attribute is requested to be set by ioremap_wc()
> method and by generic PCI memory pages/ranges mapping methods. The same
> is done by the drm_io_prot()/ttm_io_prot() functions in case if
> write-combine flag is set for vma's passed for mapping. But for some
> reason the pgprot_writecombine() method calling is ifdefed to be a
> platform-specific with MIPS system being marked as lacking of one. At the
> very least it doesn't reflect the current MIPS platform implementation.
> So in order to improve the DRM subsystem performance on MIPS with UCA
> mapping enabled, we need to have pgprot_writecombine() called for buffers=
,
> which need store operations being combined. In case if particular MIPS
> chip doesn't support the UCA attribute, the mapping will fall back to
> noncached.
>=20
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Burton <paul.burton@mips.com>
> Cc: James Hogan <jhogan@kernel.org>
> Signed-off-by: Vadim V. Vlasov <vadim.vlasov@t-platforms.ru>
> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
> ---
>  drivers/gpu/drm/drm_vm.c          | 5 +++--
>  drivers/gpu/drm/ttm/ttm_bo_util.c | 4 ++--
>  2 files changed, 5 insertions(+), 4 deletions(-)

Looks good to me:

    Reviewed-by: Paul Burton <paul.burton@mips.com>

Thanks,
    Paul