linux-kernel - [PATCH 4.4 113/190] drm/omap: fix tiled buffer stride calculations

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Date:   Wed, 11 Apr 2018 20:35:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tomi Valkeinen <tomi.valkeinen@...com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.4 113/190] drm/omap: fix tiled buffer stride calculations

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tomi Valkeinen <tomi.valkeinen@...com>


[ Upstream commit cc8dd7661ccc2d8dc88921da8e6cc7c2fcdb0341 ]

omap_gem uses page alignment for buffer stride. The related calculations
are a bit off, though, as byte stride of 4096 gets aligned to 8192,
instead of 4096.

This patch changes the code to use DIV_ROUND_UP(), which fixes those
calculations and makes them more readable.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/omapdrm/omap_gem.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -158,7 +158,7 @@ static void evict_entry(struct drm_gem_o
 	size_t size = PAGE_SIZE * n;
 	loff_t off = mmap_offset(obj) +
 			(entry->obj_pgoff << PAGE_SHIFT);
-	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
+	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
 
 	if (m > 1) {
 		int i;
@@ -415,7 +415,7 @@ static int fault_2d(struct drm_gem_objec
 	 * into account in some of the math, so figure out virtual stride
 	 * in pages
 	 */
-	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
+	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
 
 	/* We don't use vmf->pgoff since that has the fake offset: */
 	pgoff = ((unsigned long)vmf->virtual_address -