regmap: cache: Fall back to register by register read for cache defaults

If we are unable to read the cache defaults for a regmap then fall back
on attempting to read them word by word. This is going to be painfully
slow for large regmaps but might be adequate for smaller ones.

Signed-off-by: Mark Brown <broonie@kernel.org>
[maciej: Use cache_bypass around read and skipping of unreadable regs]
Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 30 insertions, 11 deletions

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 348be3a35410..cccceb599b02 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -30,7 +30,7 @@ static int regcache_hw_init(struct regmap *map)
         int i, j;
         int ret;
         int count;
-        unsigned int val;
+        unsigned int reg, val;
         void *tmp_buf;
 
         if (!map->num_reg_defaults_raw)
@@ -67,27 +67,46 @@ static int regcache_hw_init(struct regmap *map)
                 ret = regmap_raw_read(map, 0, tmp_buf,
                                       map->num_reg_defaults_raw);
                 map->cache_bypass = cache_bypass;
-                if (ret < 0)
-                        goto err_cache_free;
-
-                map->reg_defaults_raw = tmp_buf;
-                map->cache_free = 1;
+                if (ret == 0) {
+                        map->reg_defaults_raw = tmp_buf;
+                        map->cache_free = 1;
+                } else {
+                        kfree(tmp_buf);
+                }
         }
 
         /* fill the reg_defaults */
         for (i = 0, j = 0; i < map->num_reg_defaults_raw; i++) {
-                if (regmap_volatile(map, i * map->reg_stride))
+                reg = i * map->reg_stride;
+
+                if (!regmap_readable(map, reg))
                         continue;
-                val = regcache_get_val(map, map->reg_defaults_raw, i);
-                map->reg_defaults[j].reg = i * map->reg_stride;
+
+                if (regmap_volatile(map, reg))
+                        continue;
+
+                if (map->reg_defaults_raw) {
+                        val = regcache_get_val(map, map->reg_defaults_raw, i);
+                } else {
+                        bool cache_bypass = map->cache_bypass;
+
+                        map->cache_bypass = true;
+                        ret = regmap_read(map, reg, &val);
+                        map->cache_bypass = cache_bypass;
+                        if (ret != 0) {
+                                dev_err(map->dev, "Failed to read %d: %d\n",
+                                        reg, ret);
+                                goto err_free;
+                        }
+                }
+
+                map->reg_defaults[j].reg = reg;
                 map->reg_defaults[j].def = val;
                 j++;
         }
 
         return 0;
 
-err_cache_free:
-        kfree(tmp_buf);
 err_free:
         kfree(map->reg_defaults);