linux-kernel - Re: [PATCH 02/13] drm/exynos: Use FOLL

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Message-ID: <399490f0-7738-db0b-9ed4-2510d4ea8379@nvidia.com>
Date:   Wed, 7 Oct 2020 13:43:12 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
CC:     <kvm@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-samsung-soc@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <linux-s390@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Inki Dae <inki.dae@...sung.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        "Seung-Woo Kim" <sw0312.kim@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 02/13] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists

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.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Inki Dae <inki.dae@...sung.com>
> Cc: Joonyoung Shim <jy0922.shim@...sung.com>
> Cc: Seung-Woo Kim <sw0312.kim@...sung.com>
> Cc: Kyungmin Park <kyungmin.park@...sung.com>
> Cc: Kukjin Kim <kgene@...nel.org>
> Cc: Krzysztof Kozlowski <krzk@...nel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: John Hubbard <jhubbard@...dia.com>
> Cc: Jérôme Glisse <jglisse@...hat.com>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: linux-mm@...ck.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-samsung-soc@...r.kernel.org
> Cc: linux-media@...r.kernel.org
> ---
>   drivers/gpu/drm/exynos/exynos_drm_g2d.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/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 g2d_data *g2d,
>   		goto err_free;
>   	}
>   
> -	ret = pin_user_pages_fast(start, npages, FOLL_FORCE | FOLL_WRITE,
> +	ret = pin_user_pages_fast(start, npages,
> +				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
>   				  g2d_userptr->pages);
>   	if (ret != npages) {
>   		DRM_DEV_ERROR(g2d->dev,
> 

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@...dia.com>

thanks,
-- 
John Hubbard
NVIDIA