linux-kernel - [PATCH 2/2] nvmem: imx-ocotp: allow reads with arbitrary size and offset

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Date:   Tue, 23 Jul 2019 17:32:43 +0200
From:   Jose Diaz de Grenu <Jose.DiazdeGrenu@...i.com>
To:     <Jose.DiazdeGrenu@...i.com>
CC:     <srinivas.kandagatla@...aro.org>, <shawnguo@...nel.org>,
        <s.hauer@...gutronix.de>, <kernel@...gutronix.de>,
        <festevam@...il.com>, <linux-imx@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] nvmem: imx-ocotp: allow reads with arbitrary size and offset

Currently the driver only allows to read 32 aligned 32-bit chunks. This
is inconvenient when defining nvmem-cells, as they are rarely a multiple
of 32 bits in size, and that makes the nvmem-consumer hardcode offsets and
masks to extract the real value.

Remove the limitation but keep reading in 32-bit chunks from the hardware
to ensure there is no change in the behaviour.

Signed-off-by: Jose Diaz de Grenu <Jose.DiazdeGrenu@...i.com>
---
 drivers/nvmem/imx-ocotp.c | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index dc86d863563a..9590eeab85d8 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -121,16 +121,8 @@ static int imx_ocotp_read(void *context, unsigned int offset,
 			  void *val, size_t bytes)
 {
 	struct ocotp_priv *priv = context;
-	unsigned int count;
-	u32 *buf = val;
+	u8 *buf = val;
 	int i, ret;
-	u32 index;
-
-	index = offset >> 2;
-	count = bytes >> 2;
-
-	if (count > (priv->params->nregs - index))
-		count = priv->params->nregs - index;
 
 	mutex_lock(&ocotp_mutex);
 
@@ -147,9 +139,9 @@ static int imx_ocotp_read(void *context, unsigned int offset,
 		goto read_end;
 	}
 
-	for (i = index; i < (index + count); i++) {
-		*buf++ = readl(priv->base + IMX_OCOTP_OFFSET_B0W0 +
-			       i * IMX_OCOTP_OFFSET_PER_WORD);
+	for (i = offset; i < (bytes + offset); i++) {
+		u32 word_val = readl(priv->base + IMX_OCOTP_OFFSET_B0W0 +
+				     (i >> 2) * IMX_OCOTP_OFFSET_PER_WORD);
 
 		/* 47.3.1.2
 		 * For "read locked" registers 0xBADABADA will be returned and
@@ -157,9 +149,14 @@ 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 (word_val == IMX_OCOTP_READ_LOCKED_VAL)
 			imx_ocotp_clr_err_if_set(priv->base);
+
+		word_val >>= (i % 4) * 8;
+
+		*buf++ = (u8) (word_val & 0xFF);
 	}
+
 	ret = 0;
 
 read_end:
@@ -415,8 +412,8 @@ static int imx_ocotp_write(void *context, unsigned int offset, void *val,
 static struct nvmem_config imx_ocotp_nvmem_config = {
 	.name = "imx-ocotp",
 	.read_only = false,
-	.word_size = 4,
-	.stride = 4,
+	.word_size = 1,
+	.stride = 1,
 	.reg_read = imx_ocotp_read,
 	.reg_write = imx_ocotp_write,
 };