Patch "regmap: prevent noinc writes from clobbering cache" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    regmap: prevent noinc writes from clobbering cache

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     regmap-prevent-noinc-writes-from-clobbering-cache.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit be84ba88850accb1f325cbe94e524d5cd25398f1
Author: Ben Wolsieffer <ben.wolsieffer@xxxxxxxxxxx>
Date:   Wed Nov 1 10:29:27 2023 -0400

    regmap: prevent noinc writes from clobbering cache
    
    [ Upstream commit 984a4afdc87a1fc226fd657b1cd8255c13d3fc1a ]
    
    Currently, noinc writes are cached as if they were standard incrementing
    writes, overwriting unrelated register values in the cache. Instead, we
    want to cache the last value written to the register, as is done in the
    accelerated noinc handler (regmap_noinc_readwrite).
    
    Fixes: cdf6b11daa77 ("regmap: Add regmap_noinc_write API")
    Signed-off-by: Ben Wolsieffer <ben.wolsieffer@xxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20231101142926.2722603-2-ben.wolsieffer@xxxxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index b5974cbbe78f6..23574c328616f 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1495,17 +1495,19 @@ static int _regmap_raw_write_impl(struct regmap *map, unsigned int reg,
 	}
 
 	if (!map->cache_bypass && map->format.parse_val) {
-		unsigned int ival;
+		unsigned int ival, offset;
 		int val_bytes = map->format.val_bytes;
-		for (i = 0; i < val_len / val_bytes; i++) {
-			ival = map->format.parse_val(val + (i * val_bytes));
-			ret = regcache_write(map,
-					     reg + regmap_get_offset(map, i),
-					     ival);
+
+		/* Cache the last written value for noinc writes */
+		i = noinc ? val_len - val_bytes : 0;
+		for (; i < val_len; i += val_bytes) {
+			ival = map->format.parse_val(val + i);
+			offset = noinc ? 0 : regmap_get_offset(map, i / val_bytes);
+			ret = regcache_write(map, reg + offset, ival);
 			if (ret) {
 				dev_err(map->dev,
 					"Error in caching of register: %x ret: %d\n",
-					reg + regmap_get_offset(map, i), ret);
+					reg + offset, ret);
 				return ret;
 			}
 		}