linux-kernel - [PATCH] soc: imx8m: Increase the clock enable before reading the register

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Message-Id: <20221028041418.4033261-1-xiaolei.wang@windriver.com>
Date:   Fri, 28 Oct 2022 12:14:18 +0800
From:   Xiaolei Wang <xiaolei.wang@...driver.com>
To:     shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com
Cc:     l.stach@...gutronix.de, linux-imx@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] soc: imx8m: Increase the clock enable before reading the register

When executing kdump to start the second kernel,
since IMX-OCOTP has turned off the clock, the clock
needs to be re-enabled, otherwise the system will hang.

Fixes: ac34de14ac30 ("Revert "soc: imx8m: change to use platform driver"")
Signed-off-by: Xiaolei Wang <xiaolei.wang@...driver.com>
---
 drivers/soc/imx/soc-imx8m.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/soc/imx/soc-imx8m.c b/drivers/soc/imx/soc-imx8m.c
index cc57a384d74d..28144c699b0c 100644
--- a/drivers/soc/imx/soc-imx8m.c
+++ b/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
 
@@ -56,6 +57,7 @@ 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)
@@ -63,6 +65,13 @@ static u32 __init imx8mq_soc_revision(void)
 
 	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);
 
-- 
2.25.1