cpufreq: imx6: use regmap to read ocotp register

Reading the ocotp register directly is unsafe and will cause the system
to hang if its clock is not turned on in CCM. The regmap interface has
clk enabled, which can solve this problem.

Signed-off-by: tianyu2 <[e-mail]>
Signed-off-by: Viresh Kumar <[e-mail]>

drivers/cpufreq/imx6q-cpufreq.c

···
 #include <linux/pm_opp.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
 
 #define PU_SOC_VOLTAGE_NORMAL	1250000
 #define PU_SOC_VOLTAGE_HIGH	1275000
···
 
 static int imx6q_opp_check_speed_grading(struct device *dev)
 {
-	struct device_node *np;
-	void __iomem *base;
 	u32 val;
 	int ret;
 
···
 		if (ret)
 			return ret;
 	} else {
-		np = of_find_compatible_node(NULL, NULL, "fsl,imx6q-ocotp");
-		if (!np)
-			return -ENOENT;
+		struct regmap *ocotp;
 
-		base = of_iomap(np, 0);
-		of_node_put(np);
-		if (!base) {
-			dev_err(dev, "failed to map ocotp\n");
-			return -EFAULT;
-		}
+		ocotp = syscon_regmap_lookup_by_compatible("fsl,imx6q-ocotp");
+		if (IS_ERR(ocotp))
+			return -ENOENT;
 
 		/*
 		 * SPEED_GRADING[1:0] defines the max speed of ARM:
···
 		 * 2b'00: 792000000Hz;
 		 * We need to set the max speed of ARM according to fuse map.
 		 */
-		val = readl_relaxed(base + OCOTP_CFG3);
-		iounmap(base);
+		regmap_read(ocotp, OCOTP_CFG3, &val);
 	}
 
 	val >>= OCOTP_CFG3_SPEED_SHIFT;
···
 		if (ret)
 			return ret;
 	} else {
-		struct device_node *np;
-		void __iomem *base;
+		struct regmap *ocotp;
 
-		np = of_find_compatible_node(NULL, NULL, "fsl,imx6ul-ocotp");
-		if (!np)
-			np = of_find_compatible_node(NULL, NULL,
-						     "fsl,imx6ull-ocotp");
-		if (!np)
+		ocotp = syscon_regmap_lookup_by_compatible("fsl,imx6ul-ocotp");
+		if (IS_ERR(ocotp))
+			ocotp = syscon_regmap_lookup_by_compatible("fsl,imx6ull-ocotp");
+
+		if (IS_ERR(ocotp))
 			return -ENOENT;
 
-		base = of_iomap(np, 0);
-		of_node_put(np);
-		if (!base) {
-			dev_err(dev, "failed to map ocotp\n");
-			return -EFAULT;
-		}
-
-		val = readl_relaxed(base + OCOTP_CFG3);
-		iounmap(base);
+		regmap_read(ocotp, OCOTP_CFG3, &val);
 	}
 
 	/*