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From:   peng.fan@nxp.com
To:     shawnguo@kernel.org, s.hauer@pengutronix.de,
        srinivas.kandagatla@linaro.org
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        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Peng Fan <peng.fan@nxp.com>
Subject: [PATCH] nvmem: imx-ocotp: add support for the unaliged word count
Date:   Thu, 22 Oct 2020 15:44:43 +0800
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From: Peng Fan <peng.fan@nxp.com>

When offset is not 4 bytes aligned, directly shift righty by 2 bits
will cause reading out wrong data. Since imx ocotp only supports
4 bytes reading once, we need handle offset is not 4 bytes aligned
and enlarge the bytes to 4 bytes aligned. After reading finished,
copy the needed data from buffer to caller and free buffer.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/nvmem/imx-ocotp.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index 7a1ebd6fd08b..08f41328cc71 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -4,6 +4,8 @@
  *
  * Copyright (c) 2015 Pengutronix, Philipp Zabel <p.zabel@pengutronix.de>
  *
+ * Copyright 2019 NXP
+ *
  * Based on the barebox ocotp driver,
  * Copyright (c) 2010 Baruch Siach <baruch@tkos.co.il>,
  *	Orex Computed Radiography
@@ -158,22 +160,30 @@ static int imx_ocotp_read(void *context, unsigned int offset,
 {
 	struct ocotp_priv *priv = context;
 	unsigned int count;
-	u32 *buf = val;
+	u8 *buf, *p;
 	int i, ret;
-	u32 index;
+	u32 index, num_bytes;
 
 	index = offset >> 2;
-	count = bytes >> 2;
+	num_bytes = round_up((offset % 4) + bytes, 4);
+	count = num_bytes >> 2;
 
 	if (count > (priv->params->nregs - index))
 		count = priv->params->nregs - index;
 
+	p = kzalloc(num_bytes, GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
 	mutex_lock(&ocotp_mutex);
 
+	buf = p;
+
 	ret = clk_prepare_enable(priv->clk);
 	if (ret < 0) {
 		mutex_unlock(&ocotp_mutex);
 		dev_err(priv->dev, "failed to prepare/enable ocotp clk\n");
+		kfree(p);
 		return ret;
 	}
 
@@ -184,7 +194,7 @@ static int imx_ocotp_read(void *context, unsigned int offset,
 	}
 
 	for (i = index; i < (index + count); i++) {
-		*buf++ = readl(priv->base + IMX_OCOTP_OFFSET_B0W0 +
+		*(u32 *)buf = readl(priv->base + IMX_OCOTP_OFFSET_B0W0 +
 			       i * IMX_OCOTP_OFFSET_PER_WORD);
 
 		/* 47.3.1.2
@@ -193,13 +203,21 @@ static int imx_ocotp_read(void *context, unsigned int offset,
 		 * software before any new write, read or reload access can be
 		 * issued
 		 */
-		if (*(buf - 1) == IMX_OCOTP_READ_LOCKED_VAL)
+		if (*((u32 *)buf) == IMX_OCOTP_READ_LOCKED_VAL)
 			imx_ocotp_clr_err_if_set(priv);
+
+		buf += 4;
 	}
 
+	index = offset % 4;
+	memcpy(val, &p[index], bytes);
+
 read_end:
 	clk_disable_unprepare(priv->clk);
 	mutex_unlock(&ocotp_mutex);
+
+	kfree(p);
+
 	return ret;
 }
 
@@ -447,7 +465,7 @@ static struct nvmem_config imx_ocotp_nvmem_config = {
 	.name = "imx-ocotp",
 	.read_only = false,
 	.word_size = 4,
-	.stride = 4,
+	.stride = 1,
 	.reg_read = imx_ocotp_read,
 	.reg_write = imx_ocotp_write,
 };
-- 
2.28.0