iosys-map: Add offset to iosys_map_memcpy_to()

In certain situations it's useful to be able to write to an
offset of the mapping. Add a dst_offset to iosys_map_memcpy_to().

Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Christian König <christian.koenig@amd.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220216174147.3073235-2-lucas.demarchi@intel.com

drivers/gpu/drm/drm_cache.c

@@ -221,7 +221,7 @@ static void memcpy_fallback(struct iosys_map *dst,
 	if (!dst->is_iomem && !src->is_iomem) {
 		memcpy(dst->vaddr, src->vaddr, len);
 	} else if (!src->is_iomem) {
-		iosys_map_memcpy_to(dst, src->vaddr, len);
+		iosys_map_memcpy_to(dst, 0, src->vaddr, len);
 	} else if (!dst->is_iomem) {
 		memcpy_fromio(dst->vaddr, src->vaddr_iomem, len);
 	} else {

drivers/gpu/drm/drm_fb_helper.c

@@ -385,7 +385,7 @@ static void drm_fb_helper_damage_blit_real(struct drm_fb_helper *fb_helper,
 	iosys_map_incr(dst, offset); /* go to first pixel within clip rect */
 
 	for (y = clip->y1; y < clip->y2; y++) {
-		iosys_map_memcpy_to(dst, src, len);
+		iosys_map_memcpy_to(dst, 0, src, len);
 		iosys_map_incr(dst, fb->pitches[0]);
 		src += fb->pitches[0];
 	}

include/linux/iosys-map.h

@@ -220,22 +220,23 @@ static inline void iosys_map_clear(struct iosys_map *map)
 }
 
 /**
- * iosys_map_memcpy_to - Memcpy into iosys mapping
+ * iosys_map_memcpy_to - Memcpy into offset of iosys_map
  * @dst:	The iosys_map structure
+ * @dst_offset:	The offset from which to copy
  * @src:	The source buffer
  * @len:	The number of byte in src
  *
- * Copies data into a iosys mapping. The source buffer is in system
- * memory. Depending on the buffer's location, the helper picks the correct
- * method of accessing the memory.
+ * Copies data into a iosys_map with an offset. The source buffer is in
+ * system memory. Depending on the buffer's location, the helper picks the
+ * correct method of accessing the memory.
  */
-static inline void iosys_map_memcpy_to(struct iosys_map *dst, const void *src,
-				       size_t len)
+static inline void iosys_map_memcpy_to(struct iosys_map *dst, size_t dst_offset,
+				       const void *src, size_t len)
 {
 	if (dst->is_iomem)
-		memcpy_toio(dst->vaddr_iomem, src, len);
+		memcpy_toio(dst->vaddr_iomem + dst_offset, src, len);
 	else
-		memcpy(dst->vaddr, src, len);
+		memcpy(dst->vaddr + dst_offset, src, len);
 }
 
 /**