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Subject[PATCH 10/11] nvmem: imx-ocotp: clear error bit after reading locked values
Date
From: Richard Leitner <richard.leitner@skidata.com>

When reading a "read locked" value from the OCOTP controller on i.MX6
SoC's an error bit is set. This bit has to be cleared by software before
any new write, read or reload access can be issued.

Therefore clear it after we detect such an "locked read".

Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
drivers/nvmem/imx-ocotp.c | 41 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index 0d33705..0bb8d0d 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -25,6 +25,19 @@
#include <linux/platform_device.h>
#include <linux/slab.h>

+#define IMX_OCOTP_OFFSET_B0W0 0x400 /* Offset from base address of the
+ * OTP Bank0 Word0
+ */
+#define IMX_OCOTP_OFFSET_PER_WORD 0x10 /* Offset between the start addr
+ * of two consecutive OTP words.
+ */
+#define IMX_OCOTP_ADDR_CTRL 0x0000
+#define IMX_OCOTP_ADDR_CTRL_CLR 0x0008
+
+#define IMX_OCOTP_BM_CTRL_ERROR 0x00000200
+
+#define IMX_OCOTP_READ_LOCKED_VAL 0xBADABADA
+
struct ocotp_priv {
struct device *dev;
struct clk *clk;
@@ -32,6 +45,17 @@ struct ocotp_priv {
unsigned int nregs;
};

+static void imx_ocotp_clr_err_if_set(void __iomem *base)
+{
+ u32 c;
+
+ c = readl(base + IMX_OCOTP_ADDR_CTRL);
+ if (!(c & IMX_OCOTP_BM_CTRL_ERROR))
+ return;
+
+ writel(IMX_OCOTP_BM_CTRL_ERROR, base + IMX_OCOTP_ADDR_CTRL_CLR);
+}
+
static int imx_ocotp_read(void *context, unsigned int offset,
void *val, size_t bytes)
{
@@ -52,11 +76,22 @@ static int imx_ocotp_read(void *context, unsigned int offset,
dev_err(priv->dev, "failed to prepare/enable ocotp clk\n");
return ret;
}
- for (i = index; i < (index + count); i++)
- *buf++ = readl(priv->base + 0x400 + i * 0x10);

- clk_disable_unprepare(priv->clk);
+ for (i = index; i < (index + count); i++) {
+ *buf++ = readl(priv->base + IMX_OCOTP_OFFSET_B0W0 +
+ i * IMX_OCOTP_OFFSET_PER_WORD);
+
+ /* 47.3.1.2
+ * For "read locked" registers 0xBADABADA will be returned and
+ * HW_OCOTP_CTRL[ERROR] will be set. It must be cleared by
+ * software before any new write, read or reload access can be
+ * issued
+ */
+ if (*(buf - 1) == IMX_OCOTP_READ_LOCKED_VAL)
+ imx_ocotp_clr_err_if_set(priv->base);
+ }

+ clk_disable_unprepare(priv->clk);
return 0;
}

--
2.7.4
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