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Message-ID: <3365044.AohtTD8A6l@avalon>
Date: Tue, 30 Jan 2018 16:58:07 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Philippe Cornu <philippe.cornu@...com>
Cc: Yannick Fertre <yannick.fertre@...com>,
Benjamin Gaignard <benjamin.gaignard@...aro.org>,
Vincent Abriou <vincent.abriou@...com>,
David Airlie <airlied@...ux.ie>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Archit Taneja <architt@...eaurora.org>,
Andrzej Hajda <a.hajda@...sung.com>,
Fabien Dessenne <fabien.dessenne@...com>,
Mickael Reulier <mickael.reulier@...com>,
Ludovic Barre <ludovic.barre@...com>,
Alexandre Torgue <alexandre.torgue@...com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>
Subject: Re: [PATCH v2] drm/stm: drv: Improve data transfers
Hi Philippe,
Thank you for the patch.
On Tuesday, 30 January 2018 12:42:00 EET Philippe Cornu wrote:
> To optimize data transfers, align pitch on 128 bytes & height
> on 4 bytes. This optimization is not applicable on hw without MMU.
>
> Signed-off-by: Yannick Fertre <yannick.fertre@...com>
> Signed-off-by: Vincent Abriou <vincent.abriou@...com>
> Signed-off-by: Philippe Cornu <philippe.cornu@...com>
> ---
> Changes in v2: Rename stm_dumb_create() to stm_gem_cma_dumb_create() and
> move CONFIG_MMU inside the function following comments from Benjamin
> Gaignard.
>
> drivers/gpu/drm/stm/drv.c | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/stm/drv.c b/drivers/gpu/drm/stm/drv.c
> index 8fe954c27fba..8bc7e8418b8d 100644
> --- a/drivers/gpu/drm/stm/drv.c
> +++ b/drivers/gpu/drm/stm/drv.c
> @@ -31,6 +31,24 @@ static const struct drm_mode_config_funcs
> drv_mode_config_funcs = { .atomic_commit = drm_atomic_helper_commit,
> };
>
> +static int stm_gem_cma_dumb_create(struct drm_file *file,
> + struct drm_device *dev,
> + struct drm_mode_create_dumb *args)
> +{
> +#ifdef CONFIG_MMU
> + unsigned int min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> +
> + /*
> + * in order to optimize data transfer, pitch is aligned on
> + * 128 bytes, height is aligned on 4 bytes
> + */
> + args->pitch = roundup(min_pitch, 128);
> + args->height = roundup(args->height, 4);
> +#endif
> +
> + return drm_gem_cma_dumb_create_internal(file, dev, args);
In the !CONFIG_MMU case you now bypass the pitch and size calculations
performed by drm_gem_cma_dumb_create(), allowing userspace to allocate
arbitrarily large buffers. Is that intentional ?
> +}
> +
> DEFINE_DRM_GEM_CMA_FOPS(drv_driver_fops);
>
> static struct drm_driver drv_driver = {
> @@ -44,7 +62,7 @@ static struct drm_driver drv_driver = {
> .minor = 0,
> .patchlevel = 0,
> .fops = &drv_driver_fops,
> - .dumb_create = drm_gem_cma_dumb_create,
> + .dumb_create = stm_gem_cma_dumb_create,
> .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
> .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
> .gem_free_object_unlocked = drm_gem_cma_free_object,
--
Regards,
Laurent Pinchart
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