From c9b41fcf272b4926b373d21c2b83dfe374313780 Mon Sep 17 00:00:00 2001 From: Bartosz Golaszewski Date: Wed, 6 Dec 2017 15:26:21 +0100 Subject: [PATCH 1/3] regmap: allow to disable all locking mechanisms We have a use case in the at24 EEPROM driver (recently converted to using regmap instead of raw i2c/smbus calls) where we read from/write to the regmap in a loop, while protecting the entire loop with a mutex. Currently this implicitly makes us use two mutexes - one in the driver and one in regmap. While browsing the code for similar use cases I noticed a significant number of places where locking *seems* redundant. Allow users to completely disable any locking mechanisms in regmap config. Signed-off-by: Bartosz Golaszewski Signed-off-by: Mark Brown --- drivers/base/regmap/regmap.c | 9 ++++++++- include/linux/regmap.h | 5 +++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c index 8d516a9bfc01..72917b2fc10e 100644 --- a/drivers/base/regmap/regmap.c +++ b/drivers/base/regmap/regmap.c @@ -459,6 +459,11 @@ static void regmap_unlock_hwlock_irqrestore(void *__map) } #endif +static void regmap_lock_unlock_empty(void *__map) +{ + +} + static void regmap_lock_mutex(void *__map) { struct regmap *map = __map; @@ -669,7 +674,9 @@ struct regmap *__regmap_init(struct device *dev, goto err; } - if (config->lock && config->unlock) { + if (config->disable_locking) { + map->lock = map->unlock = regmap_lock_unlock_empty; + } else if (config->lock && config->unlock) { map->lock = config->lock; map->unlock = config->unlock; map->lock_arg = config->lock_arg; diff --git a/include/linux/regmap.h b/include/linux/regmap.h index 15eddc1353ba..072a90229e34 100644 --- a/include/linux/regmap.h +++ b/include/linux/regmap.h @@ -264,6 +264,9 @@ typedef void (*regmap_unlock)(void *); * field is NULL but precious_table (see below) is not, the * check is performed on such table (a register is precious if * it belongs to one of the ranges specified by precious_table). + * @disable_locking: This regmap is either protected by external means or + * is guaranteed not be be accessed from multiple threads. + * Don't use any locking mechanisms. * @lock: Optional lock callback (overrides regmap's default lock * function, based on spinlock or mutex). * @unlock: As above for unlocking. @@ -333,6 +336,8 @@ struct regmap_config { bool (*readable_reg)(struct device *dev, unsigned int reg); bool (*volatile_reg)(struct device *dev, unsigned int reg); bool (*precious_reg)(struct device *dev, unsigned int reg); + + bool disable_locking; regmap_lock lock; regmap_unlock unlock; void *lock_arg; From 81e30b189f593afbf10a7bf47f18f030f8aea3b5 Mon Sep 17 00:00:00 2001 From: Bartosz Golaszewski Date: Wed, 13 Dec 2017 10:28:10 +0100 Subject: [PATCH 2/3] regmap: rename regmap_lock_unlock_empty() to regmap_lock_unlock_none() Minor naming convention tweak. Suggested-by: Andy Shevchenko Signed-off-by: Bartosz Golaszewski Signed-off-by: Mark Brown --- drivers/base/regmap/regmap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c index 72917b2fc10e..54b1aa371c61 100644 --- a/drivers/base/regmap/regmap.c +++ b/drivers/base/regmap/regmap.c @@ -459,7 +459,7 @@ static void regmap_unlock_hwlock_irqrestore(void *__map) } #endif -static void regmap_lock_unlock_empty(void *__map) +static void regmap_lock_unlock_none(void *__map) { } @@ -675,7 +675,7 @@ struct regmap *__regmap_init(struct device *dev, } if (config->disable_locking) { - map->lock = map->unlock = regmap_lock_unlock_empty; + map->lock = map->unlock = regmap_lock_unlock_none; } else if (config->lock && config->unlock) { map->lock = config->lock; map->unlock = config->unlock; From 72465736adf2aade263a9475a1d42007fd49e703 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 12 Dec 2017 16:56:43 +0000 Subject: [PATCH 3/3] regmap: Disable debugfs when locking is disabled The recently added support for disabling the regmap internal locking left debugfs enabled for devices with the locking disabled. This is a problem since debugfs allows userspace to do things like initiate reads from the hardware which will use the scratch buffers protected by the regmap locking so could cause data corruption. For safety address this by just disabling debugfs for these devices. That is overly conservative since some of the debugfs files just read internal data structures but it's much simpler to implmement and less likely to lead to problems with tooling that works with debugfs. Reported-by: Lars-Peter Clausen Signed-off-by: Mark Brown --- drivers/base/regmap/internal.h | 8 ++++++++ drivers/base/regmap/regmap-debugfs.c | 3 +++ drivers/base/regmap/regmap.c | 1 + 3 files changed, 12 insertions(+) diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h index 8641183cac2f..53785e0e297a 100644 --- a/drivers/base/regmap/internal.h +++ b/drivers/base/regmap/internal.h @@ -77,6 +77,7 @@ struct regmap { int async_ret; #ifdef CONFIG_DEBUG_FS + bool debugfs_disable; struct dentry *debugfs; const char *debugfs_name; @@ -215,10 +216,17 @@ struct regmap_field { extern void regmap_debugfs_initcall(void); extern void regmap_debugfs_init(struct regmap *map, const char *name); extern void regmap_debugfs_exit(struct regmap *map); + +static inline void regmap_debugfs_disable(struct regmap *map) +{ + map->debugfs_disable = true; +} + #else static inline void regmap_debugfs_initcall(void) { } static inline void regmap_debugfs_init(struct regmap *map, const char *name) { } static inline void regmap_debugfs_exit(struct regmap *map) { } +static inline void regmap_debugfs_disable(struct regmap *map) { } #endif /* regcache core declarations */ diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c index 36ce3511c733..c8ecefd75d6f 100644 --- a/drivers/base/regmap/regmap-debugfs.c +++ b/drivers/base/regmap/regmap-debugfs.c @@ -529,6 +529,9 @@ void regmap_debugfs_init(struct regmap *map, const char *name) struct regmap_range_node *range_node; const char *devname = "dummy"; + if (map->debugfs_disable) + return; + /* If we don't have the debugfs root yet, postpone init */ if (!regmap_debugfs_root) { struct regmap_debugfs_node *node; diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c index 54b1aa371c61..df9ca36753ff 100644 --- a/drivers/base/regmap/regmap.c +++ b/drivers/base/regmap/regmap.c @@ -676,6 +676,7 @@ struct regmap *__regmap_init(struct device *dev, if (config->disable_locking) { map->lock = map->unlock = regmap_lock_unlock_none; + regmap_debugfs_disable(map); } else if (config->lock && config->unlock) { map->lock = config->lock; map->unlock = config->unlock;