regmap: mmio: add register clock support

Some mmio devices have a dedicated interface clock that needs
to be enabled to access their registers. This patch optionally
enables a clock before accessing registers in the regmap_bus
callbacks.

I added (devm_)regmap_init_mmio_clk variants of the init
functions that have an added clk_id string parameter. This
is passed to clk_get to request the clock from the clk
framework.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

2 files changed, 107 insertions, 19 deletions

diff --git a/drivers/base/regmap/regmap-mmio.c b/drivers/base/regmap/regmap-mmio.c
index f05fc74dd84a..98745dd77e8c 100644
--- a/drivers/base/regmap/regmap-mmio.c
+++ b/drivers/base/regmap/regmap-mmio.c
@@ -16,6 +16,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/io.h>
@@ -26,6 +27,7 @@
 struct regmap_mmio_context {
         void __iomem *regs;
         unsigned val_bytes;
+        struct clk *clk;
 };
 
 static int regmap_mmio_gather_write(void *context,
@@ -34,9 +36,16 @@ static int regmap_mmio_gather_write(void *context,
 {
         struct regmap_mmio_context *ctx = context;
         u32 offset;
+        int ret;
 
         BUG_ON(reg_size != 4);
 
+        if (ctx->clk) {
+                ret = clk_enable(ctx->clk);
+                if (ret < 0)
+                        return ret;
+        }
+
         offset = *(u32 *)reg;
 
         while (val_size) {
@@ -64,6 +73,9 @@ static int regmap_mmio_gather_write(void *context,
                 offset += ctx->val_bytes;
         }
 
+        if (ctx->clk)
+                clk_disable(ctx->clk);
+
         return 0;
 }
 
@@ -80,9 +92,16 @@ static int regmap_mmio_read(void *context,
 {
         struct regmap_mmio_context *ctx = context;
         u32 offset;
+        int ret;
 
         BUG_ON(reg_size != 4);
 
+        if (ctx->clk) {
+                ret = clk_enable(ctx->clk);
+                if (ret < 0)
+                        return ret;
+        }
+
         offset = *(u32 *)reg;
 
         while (val_size) {
@@ -110,11 +129,20 @@ static int regmap_mmio_read(void *context,
                 offset += ctx->val_bytes;
         }
 
+        if (ctx->clk)
+                clk_disable(ctx->clk);
+
         return 0;
 }
 
 static void regmap_mmio_free_context(void *context)
 {
+        struct regmap_mmio_context *ctx = context;
+
+        if (ctx->clk) {
+                clk_unprepare(ctx->clk);
+                clk_put(ctx->clk);
+        }
         kfree(context);
 }
 
@@ -128,11 +156,14 @@ static struct regmap_bus regmap_mmio = {
         .val_format_endian_default = REGMAP_ENDIAN_NATIVE,
 };
 
-static struct regmap_mmio_context *regmap_mmio_gen_context(void __iomem *regs,
+static struct regmap_mmio_context *regmap_mmio_gen_context(struct device *dev,
+                                        const char *clk_id,
+                                        void __iomem *regs,
                                         const struct regmap_config *config)
 {
         struct regmap_mmio_context *ctx;
         int min_stride;
+        int ret;
 
         if (config->reg_bits != 32)
                 return ERR_PTR(-EINVAL);
@@ -179,37 +210,59 @@ static struct regmap_mmio_context *regmap_mmio_gen_context(void __iomem *regs,
         ctx->regs = regs;
         ctx->val_bytes = config->val_bits / 8;
 
+        if (clk_id == NULL)
+                return ctx;
+
+        ctx->clk = clk_get(dev, clk_id);
+        if (IS_ERR(ctx->clk)) {
+                ret = PTR_ERR(ctx->clk);
+                goto err_free;
+        }
+
+        ret = clk_prepare(ctx->clk);
+        if (ret < 0) {
+                clk_put(ctx->clk);
+                goto err_free;
+        }
+
         return ctx;
+
+err_free:
+        kfree(ctx);
+
+        return ERR_PTR(ret);
 }
 
 /**
- * regmap_init_mmio(): Initialise register map
+ * regmap_init_mmio_clk(): Initialise register map with register clock
  *
  * @dev: Device that will be interacted with
+ * @clk_id: register clock consumer ID
  * @regs: Pointer to memory-mapped IO region
  * @config: Configuration for register map
  *
  * The return value will be an ERR_PTR() on error or a valid pointer to
  * a struct regmap.
  */
-struct regmap *regmap_init_mmio(struct device *dev,
-                                void __iomem *regs,
-                                const struct regmap_config *config)
+struct regmap *regmap_init_mmio_clk(struct device *dev, const char *clk_id,
+                                    void __iomem *regs,
+                                    const struct regmap_config *config)
 {
         struct regmap_mmio_context *ctx;
 
-        ctx = regmap_mmio_gen_context(regs, config);
+        ctx = regmap_mmio_gen_context(dev, clk_id, regs, config);
         if (IS_ERR(ctx))
                 return ERR_CAST(ctx);
 
         return regmap_init(dev, &regmap_mmio, ctx, config);
 }
-EXPORT_SYMBOL_GPL(regmap_init_mmio);
+EXPORT_SYMBOL_GPL(regmap_init_mmio_clk);
 
 /**