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Subject: Re: [PATCH 02/13] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists
To:     Daniel Vetter <daniel.vetter@ffwll.ch>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
CC:     <kvm@vger.kernel.org>, <linux-mm@kvack.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-samsung-soc@vger.kernel.org>, <linux-media@vger.kernel.org>,
        <linux-s390@vger.kernel.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
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        Joonyoung Shim <jy0922.shim@samsung.com>,
        "Seung-Woo Kim" <sw0312.kim@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Kukjin Kim <kgene@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
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References: <20201007164426.1812530-1-daniel.vetter@ffwll.ch>
 <20201007164426.1812530-3-daniel.vetter@ffwll.ch>
From:   John Hubbard <jhubbard@nvidia.com>
Message-ID: <399490f0-7738-db0b-9ed4-2510d4ea8379@nvidia.com>
Date:   Wed, 7 Oct 2020 13:43:12 -0700
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On 10/7/20 9:44 AM, Daniel Vetter wrote:
> The exynos g2d interface is very unusual, but it looks like the
> userptr objects are persistent. Hence they need FOLL_LONGTERM.
>=20
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Inki Dae <inki.dae@samsung.com>
> Cc: Joonyoung Shim <jy0922.shim@samsung.com>
> Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Kukjin Kim <kgene@kernel.org>
> Cc: Krzysztof Kozlowski <krzk@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: J=C3=A9r=C3=B4me Glisse <jglisse@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: linux-mm@kvack.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-samsung-soc@vger.kernel.org
> Cc: linux-media@vger.kernel.org
> ---
>   drivers/gpu/drm/exynos/exynos_drm_g2d.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/ex=
ynos/exynos_drm_g2d.c
> index c83f6faac9de..514fd000feb1 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> @@ -478,7 +478,8 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2=
d_data *g2d,
>   		goto err_free;
>   	}
>  =20
> -	ret =3D pin_user_pages_fast(start, npages, FOLL_FORCE | FOLL_WRITE,
> +	ret =3D pin_user_pages_fast(start, npages,
> +				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
>   				  g2d_userptr->pages);
>   	if (ret !=3D npages) {
>   		DRM_DEV_ERROR(g2d->dev,
>=20

Looks good from a pin_user_pages_fast() point of view. I'm of course not a =
exynos
developer, so we still need a look from one of those, ideally, but:

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
--=20
John Hubbard
NVIDIA