bus: imx-weim: support CS GPR configuration

For imx50-weim and imx6q-weim type of devices, there might a WEIM CS
space configuration register in General Purpose Register controller,
e.g. IOMUXC_GPR1 on i.MX6Q.

Depending on which configuration of the following 4 is chosen for given
system, IOMUXC_GPR1[11:0] should be set up as 05, 033, 0113 or 01111
correspondingly.

	CS0(128M) CS1(0M)  CS2(0M)  CS3(0M)
	CS0(64M)  CS1(64M) CS2(0M)  CS3(0M)
	CS0(64M)  CS1(32M) CS2(32M) CS3(0M)
	CS0(32M)  CS1(32M) CS2(32M) CS3(32M)

The patch creates a function for such type of devices, which scans
'ranges' property of WEIM node and build the GPR value incrementally.
Thus the WEIM CS GPR can be set up automatically at boot time.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Philippe De Muyter <phdm@macqel.be>
Tested-by: Philippe De Muyter <phdm@macqel.be>

Documentation/devicetree/bindings/bus/imx-weim.txt

@@ -8,7 +8,12 @@ The actual devices are instantiated from the child nodes of a WEIM node.
 
 Required properties:
 
- - compatible:		Should be set to "fsl,<soc>-weim"
+ - compatible:		Should contain one of the following:
+			  "fsl,imx1-weim"
+			  "fsl,imx27-weim"
+			  "fsl,imx51-weim"
+			  "fsl,imx50-weim"
+			  "fsl,imx6q-weim"
  - reg:			A resource specifier for the register space
 			(see the example below)
  - clocks:		the clock, see the example below.
@@ -19,6 +24,26 @@ Required properties:
 
 			   <cs-number> 0 <physical address of mapping> <size>
 
+Optional properties:
+
+ - fsl,weim-cs-gpr:	For "fsl,imx50-weim" and "fsl,imx6q-weim" type of
+			devices, it should be the phandle to the system General
+			Purpose Register controller that contains WEIM CS GPR
+			register, e.g. IOMUXC_GPR1 on i.MX6Q.  IOMUXC_GPR1[11:0]
+			should be set up as one of the following 4 possible
+			values depending on the CS space configuration.
+
+			IOMUXC_GPR1[11:0]    CS0    CS1    CS2    CS3
+			---------------------------------------------
+				05	    128M     0M     0M     0M
+				033          64M    64M     0M     0M
+				0113         64M    32M    32M     0M
+				01111        32M    32M    32M    32M
+
+			In case that the property is absent, the reset value or
+			what bootloader sets up in IOMUXC_GPR1[11:0] will be
+			used.
+
 Timing property for child nodes. It is mandatory, not optional.
 
  - fsl,weim-cs-timing:	The timing array, contains timing values for the
@@ -43,6 +68,7 @@ Example for an imx6q-sabreauto board, the NOR flash connected to the WEIM:
 		#address-cells = <2>;
 		#size-cells = <1>;
 		ranges = <0 0 0x08000000 0x08000000>;
+		fsl,weim-cs-gpr = <&gpr>;
 
 		nor@0,0 {
 			compatible = "cfi-flash";

drivers/bus/imx-weim.c

@@ -11,6 +11,9 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/of_device.h>
+#include <linux/mfd/syscon.h>
+#include <linux/mfd/syscon/imx6q-iomuxc-gpr.h>
+#include <linux/regmap.h>
 
 struct imx_weim_devtype {
 	unsigned int	cs_count;
@@ -56,6 +59,55 @@ static const struct of_device_id weim_id_table[] = {
 };
 MODULE_DEVICE_TABLE(of, weim_id_table);
 
+static int __init imx_weim_gpr_setup(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct property *prop;
+	const __be32 *p;
+	struct regmap *gpr;
+	u32 gprvals[4] = {
+		05,	/* CS0(128M) CS1(0M)  CS2(0M)  CS3(0M)  */
+		033,	/* CS0(64M)  CS1(64M) CS2(0M)  CS3(0M)  */
+		0113,	/* CS0(64M)  CS1(32M) CS2(32M) CS3(0M)  */
+		01111,	/* CS0(32M)  CS1(32M) CS2(32M) CS3(32M) */
+	};
+	u32 gprval = 0;
+	u32 val;
+	int cs = 0;
+	int i = 0;
+
+	gpr = syscon_regmap_lookup_by_phandle(np, "fsl,weim-cs-gpr");
+	if (IS_ERR(gpr)) {
+		dev_dbg(&pdev->dev, "failed to find weim-cs-gpr\n");
+		return 0;
+	}
+
+	of_property_for_each_u32(np, "ranges", prop, p, val) {
+		if (i % 4 == 0) {
+			cs = val;
+		} else if (i % 4 == 3 && val) {
+			val = (val / SZ_32M) | 1;
+			gprval |= val << cs * 3;
+		}
+		i++;
+	}
+
+	if (i == 0 || i % 4)
+		goto err;
+
+	for (i = 0; i < ARRAY_SIZE(gprvals); i++) {
+		if (gprval == gprvals[i]) {
+			/* Found it. Set up IOMUXC_GPR1[11:0] with it. */
+			regmap_update_bits(gpr, IOMUXC_GPR1, 0xfff, gprval);
+			return 0;
+		}
+	}
+
+err:
+	dev_err(&pdev->dev, "Invalid 'ranges' configuration\n");
+	return -EINVAL;
+}
+
 /* Parse and set the timing for this device. */
 static int __init weim_timing_setup(struct device_node *np, void __iomem *base,
 				    const struct imx_weim_devtype *devtype)
@@ -92,6 +144,12 @@ static int __init weim_parse_dt(struct platform_device *pdev,
 	struct device_node *child;
 	int ret;
 
+	if (devtype == &imx50_weim_devtype) {
+		ret = imx_weim_gpr_setup(pdev);
+		if (ret)
+			return ret;
+	}
+
 	for_each_child_of_node(pdev->dev.of_node, child) {
 		if (!child->name)
 			continue;