From 9ed3d974a26644ad57b3d4d067e279188b2038b6 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 5 Aug 2026 18:51:00 +0100 Subject: [PATCH 1/2] regcache: Use a consistent sort for defaults table When we look up registers in the defaults table we use a binary search, and we have a regcache_sort_defaults() API to help drivers that constuct their defaults tables on the fly. Unfortunately the lookup and the sort don't use the same comparison function, and to make matters worse the comparison function used during lookups is written for signed register numbers rather than the unsigned ones we actually have so can produce suprising results when some of the addresses have the top bit set. Standardise on the more explicitly coded function to ensure consistent results. Reviewed-by: Peter Ujfalusi Reviewed-by: Charles Keepax Tested-by: Charles Keepax Link: https://patch.msgid.link/20260805-regmap-regcache-sort-v1-1-162186aad8b9@kernel.org Signed-off-by: Mark Brown --- drivers/base/regmap/regcache.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c index aa8f2efed779..480bc76f9a02 100644 --- a/drivers/base/regmap/regcache.c +++ b/drivers/base/regmap/regcache.c @@ -727,14 +727,6 @@ unsigned int regcache_get_val(struct regmap *map, const void *base, return -1; } -static int regcache_default_cmp(const void *a, const void *b) -{ - const struct reg_default *_a = a; - const struct reg_default *_b = b; - - return _a->reg - _b->reg; -} - int regcache_lookup_reg(struct regmap *map, unsigned int reg) { struct reg_default key; @@ -744,7 +736,7 @@ int regcache_lookup_reg(struct regmap *map, unsigned int reg) key.def = 0; r = bsearch(&key, map->reg_defaults, map->num_reg_defaults, - sizeof(struct reg_default), regcache_default_cmp); + sizeof(struct reg_default), regcache_defaults_cmp); if (r) return r - map->reg_defaults; From 4b05ccb17f92268384d483221a577fccfc291c7a Mon Sep 17 00:00:00 2001 From: Peter Ujfalusi Date: Wed, 5 Aug 2026 16:22:50 +0300 Subject: [PATCH 2/2] regcache: Sort the local copy of an unsorted reg_defaults array regcache_lookup_reg() bsearch()es the reg_defaults array, which requires it to be sorted by ascending register address. Entries following a descending step are never found, so regcache_reg_needs_sync() reports that they need a sync and they are written to the device on every regcache_sync() even when they were never touched. Detect the misordering while reg_defaults is validated against the register stride and sort the local copy. The check needs no new loop and sort() only runs for the affected drivers, which are also warned about. Note that sort() is not stable, so for arrays with duplicated register addresses it remains unspecified which entry is found. Signed-off-by: Peter Ujfalusi Reviewed-by: Charles Keepax Tested-by: Charles Keepax Link: https://patch.msgid.link/20260805132250.2637-1-peter.ujfalusi@linux.intel.com Signed-off-by: Mark Brown --- drivers/base/regmap/regcache.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c index 480bc76f9a02..623db7a1f3bd 100644 --- a/drivers/base/regmap/regcache.c +++ b/drivers/base/regmap/regcache.c @@ -123,6 +123,8 @@ static void regcache_hw_exit(struct regmap *map) int regcache_init(struct regmap *map, const struct regmap_config *config) { + bool sort_defaults = false; + unsigned int reg_prev = 0; int count = 0; int ret; int i; @@ -149,10 +151,16 @@ int regcache_init(struct regmap *map, const struct regmap_config *config) return -EINVAL; } - for (i = 0; i < config->num_reg_defaults; i++) + for (i = 0; i < config->num_reg_defaults; i++) { if (config->reg_defaults[i].reg % map->reg_stride) return -EINVAL; + if (reg_prev > config->reg_defaults[i].reg) + sort_defaults = true; + + reg_prev = config->reg_defaults[i].reg; + } + for (i = 0; i < ARRAY_SIZE(cache_types); i++) if (cache_types[i]->type == map->cache_type) break; @@ -186,6 +194,13 @@ int regcache_init(struct regmap *map, const struct regmap_config *config) sizeof(*map->reg_defaults), GFP_KERNEL); if (!tmp_buf) return -ENOMEM; + + /* regcache_lookup_reg() bsearch()es this array */ + if (sort_defaults) { + dev_warn(map->dev, + "Driver needs fixing: Unsorted reg_defaults, sorting the copy\n"); + regcache_sort_defaults(tmp_buf, map->num_reg_defaults); + } map->reg_defaults = tmp_buf; } else if (map->num_reg_defaults_raw) { count = regcache_count_cacheable_registers(map);