regmap: debugfs: Cache offsets of valid regions for dump

Avoid doing a linear scan of the entire register map for each read() of
the debugfs register dump by recording the offsets where valid registers
exist when we first read the registers file. This assumes the set of
valid registers never changes, if this is not the case invalidation of
the cache will be required.

This could be further improved for large blocks of contiguous registers
by calculating the register we will read from within the block - currently
we do a linear scan of the block. An rbtree may also be worthwhile.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 1abcd27e2d0f..9c3b0e7a6c7d 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -15,10 +15,18 @@
 
 #include <linux/regmap.h>
 #include <linux/fs.h>
+#include <linux/list.h>
 
 struct regmap;
 struct regcache_ops;
 
+struct regmap_debugfs_off_cache {
+        struct list_head list;
+        off_t min;
+        off_t max;
+        unsigned int base_reg;
+};
+
 struct regmap_format {
         size_t buf_size;
         size_t reg_bytes;
@@ -54,6 +62,8 @@ struct regmap {
         unsigned int debugfs_reg_len;
         unsigned int debugfs_val_len;
         unsigned int debugfs_tot_len;
+
+        struct list_head debugfs_off_cache;
 #endif
 
         unsigned int max_register;