[RFC PATCH v2 1/3] mfd: syscon: Support physical regmap bus

[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, which means
we should use a physical regmap bus to define the reg_update_bits()
operation instead of the MMIO regmap bus.

Thus add a new helper for the syscon driver to allow to register a physical
regmap bus to support this new requirement.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
---
 drivers/mfd/syscon.c       | 16 ++++++++++++++--
 include/linux/mfd/syscon.h |  7 +++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 3a97816d0cba..5de74e1b6634 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -24,6 +24,7 @@
 #include <linux/slab.h>
 
 static struct platform_driver syscon_driver;
+static struct regmap_bus *syscon_phy_regmap_bus;
 
 static DEFINE_SPINLOCK(syscon_list_slock);
 static LIST_HEAD(syscon_list);
@@ -106,14 +107,18 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 	syscon_config.val_bits = reg_io_width * 8;
 	syscon_config.max_register = resource_size(&res) - reg_io_width;
 
-	regmap = regmap_init_mmio(NULL, base, &syscon_config);
+	if (syscon_phy_regmap_bus)
+		regmap = regmap_init(NULL, syscon_phy_regmap_bus, base,
+				     &syscon_config);
+	else
+		regmap = regmap_init_mmio(NULL, base, &syscon_config);
 	if (IS_ERR(regmap)) {
 		pr_err("regmap init failed\n");
 		ret = PTR_ERR(regmap);
 		goto err_regmap;
 	}
 
-	if (check_clk) {
+	if (check_clk && !syscon_phy_regmap_bus) {
 		clk = of_clk_get(np, 0);
 		if (IS_ERR(clk)) {
 			ret = PTR_ERR(clk);
@@ -172,6 +177,13 @@ static struct regmap *device_node_get_regmap(struct device_node *np,
 	return syscon->regmap;
 }
 
+void syscon_register_phys_regmap_bus(struct regmap_bus *phy_regmap_bus)
+{
+	if (phy_regmap_bus)
+		syscon_phy_regmap_bus = phy_regmap_bus;
+}
+EXPORT_SYMBOL_GPL(syscon_register_phys_regmap_bus);
+
 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 7f20e9b502a5..fbc2a2f0f414 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 +29,7 @@ extern struct regmap *syscon_regmap_lookup_by_phandle_args(
 					const char *property,
 					int arg_count,
 					unsigned int *out_args);
+extern void syscon_register_phys_regmap_bus(struct regmap_bus *phy_regmap_bus);
 #else
 static inline struct regmap *device_node_to_regmap(struct device_node *np)
 {
@@ -59,6 +61,11 @@ static inline struct regmap *syscon_regmap_lookup_by_phandle_args(
 {
 	return ERR_PTR(-ENOTSUPP);
 }
+
+static inline void
+syscon_register_phys_regmap_bus(struct regmap_bus *phy_regmap_bus)
+{
+}
 #endif
 
 #endif /* __LINUX_MFD_SYSCON_H__ */
-- 
2.17.1