From f033c26de5a5734625d2dd1dc196745fae186f1b Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Thu, 30 Mar 2023 01:10:24 +0100 Subject: regmap: Add maple tree based register cache The current state of the art for sparse register maps is the rbtree cache. This works well for most applications but isn't always ideal for sparser register maps since the rbtree can get deep, requiring a lot of walking. Fortunately the kernel has a data structure intended to address this very problem, the maple tree. Provide an initial implementation of a register cache based on the maple tree to start taking advantage of it. The entries stored in the maple tree are arrays of register values, with the maple tree keys holding the register addresses. We store data in host native format rather than device native format as we do for rbtree, this will be a benefit for devices where we don't marshal data within regmap and simplifies the code but will result in additional CPU overhead when syncing the cache on devices where we do marshal data in regmap. This should work well for a lot of devices, though there's some additional areas that could be looked at such as caching the last accessed entry like we do for rbtree and trying to minimise the maple tree level locking. We should also use bulk writes rather than single register writes when resyncing the cache where possible, even if we don't store in device native format. Very small register maps may continue to to better with rbtree longer term. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230325-regcache-maple-v3-2-23e271f93dc7@kernel.org Signed-off-by: Mark Brown --- include/linux/regmap.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/regmap.h b/include/linux/regmap.h index b63204d51b35..4d55ac88ba9e 100644 --- a/include/linux/regmap.h +++ b/include/linux/regmap.h @@ -51,6 +51,7 @@ enum regcache_type { REGCACHE_NONE, REGCACHE_RBTREE, REGCACHE_FLAT, + REGCACHE_MAPLE, }; /** -- cgit v1.2.3