ARM: imx: add speed grading check for i.mx6 soc

The fuse map of speed_grading[1:0] defines the max speed
of ARM, see below the definition:

2b'11: 1200000000Hz;
2b'10: 996000000Hz;
2b'01: 852000000Hz; -- i.MX6Q Only, exclusive with 996MHz.
2b'00: 792000000Hz;

Need to remove all illegal setpoints according to fuse
map.
Signed-off-by: NAnson Huang <b20788@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/mach-imx6q.c

@@ -253,8 +253,10 @@ static void __init imx6q_init_machine(void)
 #define OCOTP_CFG3			0x440
 #define OCOTP_CFG3_SPEED_SHIFT		16
 #define OCOTP_CFG3_SPEED_1P2GHZ		0x3
+#define OCOTP_CFG3_SPEED_996MHZ		0x2
+#define OCOTP_CFG3_SPEED_852MHZ		0x1
 
-static void __init imx6q_opp_check_1p2ghz(struct device *cpu_dev)
+static void __init imx6q_opp_check_speed_grading(struct device *cpu_dev)
 {
 	struct device_node *np;
 	void __iomem *base;
@@ -272,11 +274,29 @@ static void __init imx6q_opp_check_1p2ghz(struct device *cpu_dev)
 		goto put_node;
 	}
 
+	/*
+	 * SPEED_GRADING[1:0] defines the max speed of ARM:
+	 * 2b'11: 1200000000Hz;
+	 * 2b'10: 996000000Hz;
+	 * 2b'01: 852000000Hz; -- i.MX6Q Only, exclusive with 996MHz.
+	 * 2b'00: 792000000Hz;
+	 * We need to set the max speed of ARM according to fuse map.
+	 */
 	val = readl_relaxed(base + OCOTP_CFG3);
 	val >>= OCOTP_CFG3_SPEED_SHIFT;
-	if ((val & 0x3) != OCOTP_CFG3_SPEED_1P2GHZ)
+	val &= 0x3;
+
+	if (val != OCOTP_CFG3_SPEED_1P2GHZ)
 		if (dev_pm_opp_disable(cpu_dev, 1200000000))
 			pr_warn("failed to disable 1.2 GHz OPP\n");
+	if (val < OCOTP_CFG3_SPEED_996MHZ)
+		if (dev_pm_opp_disable(cpu_dev, 996000000))
+			pr_warn("failed to disable 996 MHz OPP\n");
+	if (cpu_is_imx6q()) {
+		if (val != OCOTP_CFG3_SPEED_852MHZ)
+			if (dev_pm_opp_disable(cpu_dev, 852000000))
+				pr_warn("failed to disable 852 MHz OPP\n");
+	}
 
 put_node:
 	of_node_put(np);
@@ -302,7 +322,7 @@ static void __init imx6q_opp_init(void)
 		goto put_node;
 	}
 
-	imx6q_opp_check_1p2ghz(cpu_dev);
+	imx6q_opp_check_speed_grading(cpu_dev);
 
 put_node:
 	of_node_put(np);