[RFC PATCH v2 2/3] regmap: mmio: allow reset control in a MMIO regmap

[Jeremy Kerr <jk@xxxxxxxxxxxxxxxxxxxx>]

A syscon device may need to be taken out of reset before functioning -
this change adds a facility to attach a reset control to a mmio regmap,
and performs the necessary deassert/assert operations on the reset
controller on attach/detach.

Signed-off-by: Jeremy Kerr <jk@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/base/regmap/regmap-mmio.c | 22 ++++++++++++++++++++++
 include/linux/regmap.h            |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/drivers/base/regmap/regmap-mmio.c b/drivers/base/regmap/regmap-mmio.c
index 3ccdd86a97e7..e2611de73b42 100644
--- a/drivers/base/regmap/regmap-mmio.c
+++ b/drivers/base/regmap/regmap-mmio.c
@@ -8,6 +8,7 @@
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/reset.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
 #include <linux/swab.h>
@@ -22,6 +23,8 @@ struct regmap_mmio_context {
 	bool attached_clk;
 	struct clk *clk;
 
+	struct reset_control *reset;
+
 	void (*reg_write)(struct regmap_mmio_context *ctx,
 			  unsigned int reg, unsigned int val);
 	unsigned int (*reg_read)(struct regmap_mmio_context *ctx,
@@ -633,4 +636,23 @@ void regmap_mmio_detach_clk(struct regmap *map)
 }
 EXPORT_SYMBOL_GPL(regmap_mmio_detach_clk);
 
+int regmap_mmio_attach_reset(struct regmap *map, struct reset_control *reset)
+{
+	struct regmap_mmio_context *ctx = map->bus_context;
+
+	ctx->reset = reset;
+
+	return reset_control_deassert(ctx->reset);
+}
+EXPORT_SYMBOL_GPL(regmap_mmio_attach_reset);
+
+void regmap_mmio_detach_reset(struct regmap *map)
+{
+	struct regmap_mmio_context *ctx = map->bus_context;
+
+	reset_control_assert(ctx->reset);
+	ctx->reset = NULL;
+}
+EXPORT_SYMBOL_GPL(regmap_mmio_detach_reset);
+
 MODULE_LICENSE("GPL v2");
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index ca3434dca3a0..b0c7a747c06f 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -34,6 +34,7 @@ struct spmi_device;
 struct regmap;
 struct regmap_range_cfg;
 struct regmap_field;
+struct reset_control;
 struct snd_ac97;
 struct sdw_slave;
 
@@ -1150,6 +1151,8 @@ bool regmap_ac97_default_volatile(struct device *dev, unsigned int reg);
 
 int regmap_mmio_attach_clk(struct regmap *map, struct clk *clk);
 void regmap_mmio_detach_clk(struct regmap *map);
+int regmap_mmio_attach_reset(struct regmap *map, struct reset_control *reset);
+void regmap_mmio_detach_reset(struct regmap *map);
 void regmap_exit(struct regmap *map);
 int regmap_reinit_cache(struct regmap *map,
 			const struct regmap_config *config);
-- 
2.35.1