regmap: Add missing cache_only checks

The current behaviour around cache_only is slightly inconsistent,
most paths will only check cache_only if cache_bypass is false,
and will return -EBUSY if a read attempts to go to the hardware
whilst cache_only is true. However, a couple of paths will not check
cache_only at all.  The most notable of these being regmap_raw_read
which will check cache_only in the case it processes the transaction
one register at a time, but not in the case it handles them as a
block. In the typical case a device has been put into cache_only
whilst powered down this can cause physical reads to happen whilst the
device is unavailable.

Add a check in regmap_raw_read and move the check in regmap_noinc_read,
adding a check for cache_bypass, such that all paths are covered and
consistent.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230601101036.1499612-2-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index db7851f..f337c79 100644 (file)
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2981,6 +2981,11 @@ int regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
                size_t chunk_count, chunk_bytes;
                size_t chunk_regs = val_count;
 
+               if (!map->cache_bypass && map->cache_only) {
+                       ret = -EBUSY;
+                       goto out;
+               }
+
                if (!map->read) {
                        ret = -ENOTSUPP;
                        goto out;
@@ -3076,18 +3081,19 @@ int regmap_noinc_read(struct regmap *map, unsigned int reg,
                goto out_unlock;
        }
 
+       /*
+        * We have not defined the FIFO semantics for cache, as the
+        * cache is just one value deep. Should we return the last
+        * written value? Just avoid this by always reading the FIFO
+        * even when using cache. Cache only will not work.
+        */
+       if (!map->cache_bypass && map->cache_only) {
+               ret = -EBUSY;
+               goto out_unlock;
+       }
+
        /* Use the accelerated operation if we can */
        if (map->bus->reg_noinc_read) {
-               /*
-                * We have not defined the FIFO semantics for cache, as the
-                * cache is just one value deep. Should we return the last
-                * written value? Just avoid this by always reading the FIFO
-                * even when using cache. Cache only will not work.
-                */
-               if (map->cache_only) {
-                       ret = -EBUSY;
-                       goto out_unlock;
-               }
                ret = regmap_noinc_readwrite(map, reg, val, val_len, false);
                goto out_unlock;
        }