Add reset control for mfd syscon devices

Simple syscon devices may require deassertion of a reset signal in order to access their register set. This change adds the resets property from reset.yaml#/properties/resets (referenced through core.yaml), specifying a maxItems of 1 for a single (optional) reset descriptor.

This will allow a future change to the syscon driver to implement reset control.

Signed-off-by Jeremy Kerr <[email protected]>

Acked-by Rob Herring <[email protected]>

---
 Documentation/devicetree/bindings/mfd/syscon.yaml | 3 +++
 1 file changed, 3 insertions(+)

Simple syscon devices may require deassertion of a reset signal in order to access their register set. Rather than requiring a custom driver to implement this, we can use the generic "resets" specifiers to link a reset line to the syscon.

This change adds an optional reset line to the syscon device description, and deasserts the reset if detected.

Signed-off-by Jeremy Kerr <[email protected]>

Reviewed-by Arnd Bergmann <[email protected]>

---
v2:
* do reset control in the early of_syscon_register() path, rather than the platform device init, which isn't used.
v3:
* use a direct reset_control_deassert rather than handling in the regmap
v4:
* collapse unnecessary else block

---
 drivers/mfd/syscon.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

Simple syscon devices may require deassertion of a reset signal in order to access their register set. Rather than requiring a custom driver to implement this, we can use the generic "resets" specifiers to link a reset line to the syscon.

This change adds an optional reset line to the syscon device description, and deasserts the reset if detected.

Signed-off-by Jeremy Kerr <[email protected]>

Reviewed-by Arnd Bergmann <[email protected]>

---
v2:
* do reset control in the early of_syscon_register() path, rather than the platform device init, which isn't used.
v3:
* use a direct reset_control_deassert rather than handling in the regmap
v4:
* collapse unnecessary else block

---
 drivers/mfd/syscon.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

drivers/mfd/syscon.c +1 -0

index bdb2ce7ff03b..57b29c325131 100644
@@ -20,6 +20,7 @@
 #include <linux/platform_data/syscon.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
+#include <linux/reset.h>
 #include <linux/mfd/syscon.h>
 #include <linux/slab.h>
 

drivers/mfd/syscon.c +19 -6

 	struct list_head list;
 };
 

@@ -40,7 +42,7 @@ static const struct regmap_config syscon_regmap_config = {
 	.reg_stride = 4,
 };
 
-static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
+static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 {
 	struct clk *clk;
 	struct syscon *syscon;

@@ -50,6 +52,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 	int ret;
 	struct regmap_config syscon_config = syscon_regmap_config;
 	struct resource res;
+	struct reset_control *reset;
 
 	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
 	if (!syscon)

@@ -114,7 +117,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 		goto err_regmap;
 	}
 
-	if (check_clk) {
+	if (check_res) {
 		clk = of_clk_get(np, 0);
 		if (IS_ERR(clk)) {
 			ret = PTR_ERR(clk);

@@ -124,8 +127,18 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 		} else {
 			ret = regmap_mmio_attach_clk(regmap, clk);
 			if (ret)
-				goto err_attach;
+				goto err_attach_clk;
 		}
+
+		reset = of_reset_control_get_optional_exclusive(np, NULL);
+		if (IS_ERR(reset)) {
+			ret = PTR_ERR(reset);
+			goto err_attach_clk;
+		}
+
+		ret = reset_control_deassert(reset);
+		if (ret)
+			goto err_reset;
 	}
 
 	syscon->regmap = regmap;

@@ -137,7 +150,9 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 
 	return syscon;
 
-err_attach:
+err_reset:
+	reset_control_put(reset);
+err_attach_clk:
 	if (!IS_ERR(clk))
 		clk_put(clk);
 err_clk:

@@ -150,7 +165,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 }
 
 static struct regmap *device_node_get_regmap(struct device_node *np,
-					     bool check_clk)
+					     bool check_res)
 {
 	struct syscon *entry, *syscon = NULL;
 

@@ -165,7 +180,7 @@ static struct regmap *device_node_get_regmap(struct device_node *np,
 	spin_unlock(&syscon_list_slock);
 
 	if (!syscon)
-		syscon = of_syscon_register(np, check_clk);
+		syscon = of_syscon_register(np, check_res);
 
 	if (IS_ERR(syscon))
 		return ERR_CAST(syscon);

Signature · 1 line

2.38.1