[RFC PATCH 1/3] mfd: syscon: Add reg_update_bits() callback support

[Baolin Wang <baolin.wang7@gmail.com>]

Some platforms such as Spreadtrum platform, define a special method to
update bits of the registers instead of reading and writing, thus add
a new reg_update_bits() callback for struct regmap_config and a helper
for syscon driver to support this new feature.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
---
 drivers/mfd/syscon.c       | 10 ++++++++++
 include/linux/mfd/syscon.h |  8 ++++++++
 include/linux/regmap.h     |  4 ++++
 3 files changed, 22 insertions(+)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 3a97816..cf6efe2 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -34,6 +34,8 @@ struct syscon {
 	struct list_head list;
 };
 
+static regmap_hw_reg_update_bits reg_update_bits;
+
 static const struct regmap_config syscon_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
@@ -105,6 +107,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 	syscon_config.reg_stride = reg_io_width;
 	syscon_config.val_bits = reg_io_width * 8;
 	syscon_config.max_register = resource_size(&res) - reg_io_width;
+	syscon_config.reg_update_bits = reg_update_bits;
 
 	regmap = regmap_init_mmio(NULL, base, &syscon_config);
 	if (IS_ERR(regmap)) {
@@ -172,6 +175,13 @@ static struct regmap *device_node_get_regmap(struct device_node *np,
 	return syscon->regmap;
 }
 
+void syscon_register_reg_update_bits(regmap_hw_reg_update_bits hw_reg_update_bits)
+{
+	if (hw_reg_update_bits)
+		reg_update_bits = hw_reg_update_bits;
+}
+EXPORT_SYMBOL_GPL(syscon_register_reg_update_bits);
+
 struct regmap *device_node_to_regmap(struct device_node *np)
 {
 	return device_node_get_regmap(np, false);
diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
index 7f20e9b..b64ef84 100644
--- a/include/linux/mfd/syscon.h
+++ b/include/linux/mfd/syscon.h
@@ -13,6 +13,7 @@
 
 #include <linux/err.h>
 #include <linux/errno.h>
+#include <linux/regmap.h>
 
 struct device_node;
 
@@ -28,6 +29,8 @@ extern struct regmap *syscon_regmap_lookup_by_phandle_args(
 					const char *property,
 					int arg_count,
 					unsigned int *out_args);
+extern void
+syscon_register_reg_update_bits(regmap_hw_reg_update_bits hw_reg_update_bits);
 #else
 static inline struct regmap *device_node_to_regmap(struct device_node *np)
 {
@@ -59,6 +62,11 @@ static inline struct regmap *syscon_regmap_lookup_by_phandle_args(
 {
 	return ERR_PTR(-ENOTSUPP);
 }
+
+static inline void
+syscon_register_reg_update_bits(regmap_hw_reg_update_bits hw_reg_update_bits)
+{
+}
 #endif
 
 #endif /* __LINUX_MFD_SYSCON_H__ */
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 40b0716..78c1036 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -340,6 +340,8 @@ struct regmap_access_table {
  *		  read operation on a bus such as SPI, I2C, etc. Most of the
  *		  devices do not need this.
  * @reg_write:	  Same as above for writing.
+ * @reg_update_bits: Optional, should only be provided for devices whose update
+ *		     operation cannot be represented as read and write.
  * @fast_io:	  Register IO is fast. Use a spinlock instead of a mutex
  *	     	  to perform locking. This field is ignored if custom lock/unlock
  *	     	  functions are used (see fields lock/unlock of struct regmap_config).
@@ -416,6 +418,8 @@ struct regmap_config {
 
 	int (*reg_read)(void *context, unsigned int reg, unsigned int *val);
 	int (*reg_write)(void *context, unsigned int reg, unsigned int val);
+	int (*reg_update_bits)(void *context, unsigned int reg,
+			       unsigned int mask, unsigned int val);
 
 	bool fast_io;
 
-- 
1.9.1