From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 22 Dec 2016 08:36:34 +0000 (+0000)
Subject: drm: Optimise power-of-two alignments in drm_mm_scan_add_block()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9a956b1548794033d5b893d6d6fcc00b197cfc9b;p=linux-beck.git

drm: Optimise power-of-two alignments in drm_mm_scan_add_block()

For power-of-two alignments, we can avoid the 64bit divide and do a
simple bitwise add instead.

v2: s/alignment_mask/remainder_mask/

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-32-chris@chris-wilson.co.uk
---

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 189ab84c5a59..0441d84fba74 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -742,8 +742,12 @@ void drm_mm_scan_init_with_range(struct drm_mm_scan *scan,
 
 	scan->mm = mm;
 
+	if (alignment <= 1)
+		alignment = 0;
+
 	scan->color = color;
 	scan->alignment = alignment;
+	scan->remainder_mask = is_power_of_2(alignment) ? alignment - 1 : 0;
 	scan->size = size;
 	scan->flags = flags;
 
@@ -811,7 +815,10 @@ bool drm_mm_scan_add_block(struct drm_mm_scan *scan,
 	if (scan->alignment) {
 		u64 rem;
 
-		div64_u64_rem(adj_start, scan->alignment, &rem);
+		if (likely(scan->remainder_mask))
+			rem = adj_start & scan->remainder_mask;
+		else
+			div64_u64_rem(adj_start, scan->alignment, &rem);
 		if (rem) {
 			adj_start -= rem;
 			if (scan->flags != DRM_MM_CREATE_TOP)
diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
index 606336fc229a..d6701d56ea74 100644
--- a/include/drm/drm_mm.h
+++ b/include/drm/drm_mm.h
@@ -110,6 +110,7 @@ struct drm_mm_scan {
 
 	u64 size;
 	u64 alignment;
+	u64 remainder_mask;
 
 	u64 range_start;
 	u64 range_end;