linux-kernel - [PATCH V2 3/3] nvmem: imx-ocotp: handling clock

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Message-Id: <1461173177-11930-3-git-send-email-van.freenix@gmail.com>
Date:	Thu, 21 Apr 2016 01:26:17 +0800
From:	Peng Fan <van.freenix@...il.com>
To:	shawnguo@...nel.org, srinivas.kandagatla@...aro.org,
	maxime.ripard@...e-electrons.com
Cc:	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, van.freenix@...il.com
Subject: [PATCH V2 3/3] nvmem: imx-ocotp: handling clock

Before access ocotp nvmem area, the clock should be enabled.
Or, `hexdump nvmem` will hang the system. So, use such flow:
"
  1. clock_enable_prepare
  2. read nvmem ocotp area
  3. clock_disable_unprepare
"

Signed-off-by: Peng Fan <van.freenix@...il.com>
Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc: Shawn Guo <shawnguo@...nel.org>
---

V2:
 Follow Fabio's comments, check return value of clk_prepare_enable

 drivers/nvmem/imx-ocotp.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index d7796eb..3f1dd9f 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -15,6 +15,7 @@
  * http://www.gnu.org/copyleft/gpl.html
  */
 
+#include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -27,6 +28,7 @@
 
 struct ocotp_priv {
 	struct device *dev;
+	struct clk *clk;
 	void __iomem *base;
 	unsigned int nregs;
 };
@@ -37,7 +39,7 @@ static int imx_ocotp_read(void *context, const void *reg, size_t reg_size,
 	struct ocotp_priv *priv = context;
 	unsigned int offset = *(u32 *)reg;
 	unsigned int count;
-	int i;
+	int i, ret;
 	u32 index;
 
 	index = offset >> 2;
@@ -46,11 +48,19 @@ static int imx_ocotp_read(void *context, const void *reg, size_t reg_size,
 	if (count > (priv->nregs - index))
 		count = priv->nregs - index;
 
+	ret = clk_prepare_enable(priv->clk);
+	if (ret < 0) {
+		dev_err(priv->dev, "failed to prepare/enable ocotp clk\n");
+		return ret;
+	}
+
 	for (i = index; i < (index + count); i++) {
 		*(u32 *)val = readl(priv->base + 0x400 + i * 0x10);
 		val += 4;
 	}
 
+	clk_disable_unprepare(priv->clk);
+
 	return 0;
 }
 
@@ -112,6 +122,10 @@ static int imx_ocotp_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->base))
 		return PTR_ERR(priv->base);
 
+	priv->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(priv->clk))
+		return PTR_ERR(priv->clk);
+
 	of_id = of_match_device(imx_ocotp_dt_ids, dev);
 	priv->nregs = (unsigned int)of_id->data;
 	imx_ocotp_regmap_config.max_register = 4 * priv->nregs - 4;
-- 
2.6.6