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From:   Ben Wolsieffer <ben.wolsieffer@hefring.com>
To:     linux-kernel@vger.kernel.org
Cc:     Mark Brown <broonie@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Ben Whitten <ben.whitten@gmail.com>,
        Ben Wolsieffer <ben.wolsieffer@hefring.com>
Subject: [PATCH] regmap: prevent noinc writes from clobbering cache
Date:   Wed,  1 Nov 2023 10:29:27 -0400
Message-ID: <20231101142926.2722603-2-ben.wolsieffer@hefring.com>
MIME-Version: 1.0
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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@hefring.com>
---
 drivers/base/regmap/regmap.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 234a84ecde8b..ea6157747199 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1620,17 +1620,19 @@ 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;
 			}
 		}
-- 
2.42.0