regmap: Use regcache_mark_dirty() to indicate power loss or reset

Existing regmap users call regcache_mark_dirty() as part of the
suspend/resume sequence, to tell regcache that non-default values need to
be resynced post-resume.  Add an internal "no_sync_defaults" regmap flag
to remember this state, so that regcache_sync() can differentiate between
these two cases:

1) HW was reset, so any cache values that match map->reg_defaults can be
safely skipped.  On some chips there are a lot of registers in the
reg_defaults list, so this optimization speeds things up quite a bit.

2) HW was not reset (maybe it was just clock-gated), so if we cached
any writes, they should be sent to the hardware regardless of whether
they match the HW default.  Currently this will write out all values in
the regcache, since we don't maintain per-register dirty bits.

Suggested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index a13587b..b2b2849 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -131,7 +131,10 @@ struct regmap {
 	struct reg_default *reg_defaults;
 	const void *reg_defaults_raw;
 	void *cache;
+	/* if set, the cache contains newer data than the HW */
 	u32 cache_dirty;
+	/* if set, the HW registers are known to match map->reg_defaults */
+	bool no_sync_defaults;
 
 	struct reg_default *patch;
 	int patch_regs;