linux-kernel - [PATCH v2] drm/stm: drv: Improve data transfers

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Date:   Tue, 30 Jan 2018 11:42:00 +0100
From:   Philippe Cornu <philippe.cornu@...com>
To:     Yannick Fertre <yannick.fertre@...com>,
        Philippe Cornu <philippe.cornu@...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>,
        "Laurent Pinchart" <Laurent.pinchart@...asonboard.com>
CC:     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: [PATCH v2] drm/stm: drv: Improve data transfers

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);
+}
+
 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,
-- 
2.15.1