soc: imx8m: Enable OCOTP clock before reading the register

Commit 7d98140 ("soc: imx8m: change to use platform driver") ever
removed the dependency on bootloader for enabling OCOTP clock.  It
helped to fix a kexec kernel hang issue.  But unfortunately it caused
a regression on CAAM driver and got reverted.

This is the second try to enable the OCOTP clock by directly calling
clock API instead of indirectly enabling the clock via nvmem API.

Fixes: ac34de1 ("Revert "soc: imx8m: change to use platform driver"")
Signed-off-by: Xiaolei Wang <[email protected]>
Reviewed-by: Lucas Stach <[email protected]>
Signed-off-by: Shawn Guo <[email protected]>

Author: xiaoleiwang123456

drivers/soc/imx/soc-imx8m.c

@@ -11,6 +11,7 @@
 #include <linux/platform_device.h>
 #include <linux/arm-smccc.h>
 #include <linux/of.h>
+#include <linux/clk.h>
 
 #define REV_B1				0x21
 
@@ -56,13 +57,21 @@ static u32 __init imx8mq_soc_revision(void)
 	void __iomem *ocotp_base;
 	u32 magic;
 	u32 rev;
+	struct clk *clk;
 
 	np = of_find_compatible_node(NULL, NULL, "fsl,imx8mq-ocotp");
 	if (!np)
 		return 0;
 
 	ocotp_base = of_iomap(np, 0);
 	WARN_ON(!ocotp_base);
+	clk = of_clk_get_by_name(np, NULL);
+	if (!clk) {
+		WARN_ON(!clk);
+		return 0;
+	}
+
+	clk_prepare_enable(clk);
 
 	/*
 	 * SOC revision on older imx8mq is not available in fuses so query
@@ -79,6 +88,8 @@ static u32 __init imx8mq_soc_revision(void)
 	soc_uid <<= 32;
 	soc_uid |= readl_relaxed(ocotp_base + OCOTP_UID_LOW);
 
+	clk_disable_unprepare(clk);
+	clk_put(clk);
 	iounmap(ocotp_base);
 	of_node_put(np);