Re: [PATCH 2/4] i2c: i2c-ocores: Use reg-shift property

From: Ganesan Ramalingam <ganesanr-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>

Deprecate 'regstep' property and use the standard 'reg-shift' property
for register offset shifts. 'regstep' will still be supported as an
optional property, but will give a warning when used.

Signed-off-by: Ganesan Ramalingam <ganesanr-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
Signed-off-by: Jayachandran C <jayachandranc-oSioyQM9ZPnuBjGU1YDckgC/G2K4zDHf@public.gmane.org>
---
 .../devicetree/bindings/i2c/i2c-ocores.txt         |    8 +++-
 drivers/i2c/busses/i2c-ocores.c                    |   39 ++++++++++++--------
 include/linux/i2c-ocores.h                         |    2 +-
 3 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
index bfec894..1c9334b 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt

@@ -4,11 +4,14 @@ Required properties:
 - compatible      : "opencores,i2c-ocores"
 - reg             : bus address start and address range size of device
 - interrupts      : interrupt number
-- regstep         : size of device registers in bytes
 - clock-frequency : frequency of bus clock in Hz
 - #address-cells  : should be <1>
 - #size-cells     : should be <0>
 
+Optional properties:
+- reg-shift       : device register offsets are shifted by this value
+- regstep         : deprecated, use reg-shift above
+
 Example:
 
 	i2c0: ocores@a0000000 {

@@ -17,9 +20,10 @@ Example:
 		compatible = "opencores,i2c-ocores";
 		reg = <0xa0000000 0x8>;
 		interrupts = <10>;
-		regstep = <1>;
 		clock-frequency = <20000000>;
 
+		reg-shift = <0>;	/* 8 bit registers */
+
 		dummy@60 {
 			compatible = "dummy";
 			reg = <0x60>;

diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
index e8159db..fb8db30 100644
--- a/drivers/i2c/busses/i2c-ocores.c
+++ b/drivers/i2c/busses/i2c-ocores.c

@@ -25,10 +25,11 @@
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/of_i2c.h>
+#include <linux/log2.h>
 
 struct ocores_i2c {
 	void __iomem *base;
-	int regstep;
+	int reg_shift;
 	wait_queue_head_t wait;
 	struct i2c_adapter adap;
 	struct i2c_msg *msg;

@@ -71,12 +72,12 @@ struct ocores_i2c {
 
 static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
 {
-	iowrite8(value, i2c->base + reg * i2c->regstep);
+	iowrite8(value, i2c->base + (reg << i2c->reg_shift));
 }
 
 static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
 {
-	return ioread8(i2c->base + reg * i2c->regstep);
+	return ioread8(i2c->base + (reg << i2c->reg_shift));
 }
 
 static void ocores_process(struct ocores_i2c *i2c)

@@ -219,22 +220,30 @@ static struct i2c_adapter ocores_adapter = {
 static int ocores_i2c_of_probe(struct platform_device *pdev,
 				struct ocores_i2c *i2c)
 {
-	const __be32* val;
-
-	val = of_get_property(pdev->dev.of_node, "regstep", NULL);
-	if (!val) {
-		dev_err(&pdev->dev, "Missing required parameter 'regstep'\n");
-		return -ENODEV;
-	}
-	i2c->regstep = be32_to_cpup(val);
+	struct device_node *np = pdev->dev.of_node;
+	u32 val;
+
+	if (of_property_read_u32(np, "reg-shift", &val)) {
+		/* no 'reg-shift', check for deprecated 'regstep' */
+		if (!of_property_read_u32(np, "regstep", &val)) {
+			if (!is_power_of_2(val)) {
+				dev_err(&pdev->dev, "invalid regstep %d\n",
+					val);
+				return -EINVAL;
+			}
+			i2c->reg_shift = ilog2(val);
+			dev_warn(&pdev->dev,
+				"regstep property deprecated, use reg-shift\n");
+		}
+	} else
+		i2c->reg_shift = val;