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From:   Yogesh Gaur <yogeshnarayan.gaur@nxp.com>
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        Yogesh Gaur <yogeshnarayan.gaur@nxp.com>
Subject: [PATCH] mtd: devices: m25p80: Make sure WRITE_EN is issued before each write
Date:   Wed, 13 Jun 2018 11:39:18 +0530
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Some SPI controllers can't write nor->page_size bytes in a single step
because their TX FIFO is too small, but when that happens we should
make sure a WRITE_EN command before each write access and READ_SR command
after each write access is issued.

The core is already taking care of that, so all we have to do here is
return the actual number of bytes that were written during the
spi_mem_exec_op() operation.

Signed-off-by: Yogesh Gaur <yogeshnarayan.gaur@nxp.com>
---
 drivers/mtd/devices/m25p80.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index e84563d..60224fe 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -72,7 +72,6 @@ static ssize_t m25p80_write(struct spi_nor *nor, loff_t to, size_t len,
 				   SPI_MEM_OP_ADDR(nor->addr_width, to, 1),
 				   SPI_MEM_OP_DUMMY(0, 1),
 				   SPI_MEM_OP_DATA_OUT(len, buf, 1));
-	size_t remaining = len;
 	int ret;
 
 	/* get transfer protocols. */
@@ -84,22 +83,16 @@ static ssize_t m25p80_write(struct spi_nor *nor, loff_t to, size_t len,
 	if (nor->program_opcode == SPINOR_OP_AAI_WP && nor->sst_write_second)
 		op.addr.nbytes = 0;
 
-	while (remaining) {
-		op.data.nbytes = remaining < UINT_MAX ? remaining : UINT_MAX;
-		ret = spi_mem_adjust_op_size(flash->spimem, &op);
-		if (ret)
-			return ret;
-
-		ret = spi_mem_exec_op(flash->spimem, &op);
-		if (ret)
-			return ret;
+	ret = spi_mem_adjust_op_size(flash->spimem, &op);
+	if (ret)
+		return ret;
+	op.data.nbytes = len < op.data.nbytes ? len : op.data.nbytes;
 
-		op.addr.val += op.data.nbytes;
-		remaining -= op.data.nbytes;
-		op.data.buf.out += op.data.nbytes;
-	}
+	ret = spi_mem_exec_op(flash->spimem, &op);
+	if (ret)
+		return ret;
 
-	return len;
+	return op.data.nbytes;
 }
 
 /*
-- 
2.7.4

Patch is based on the spi-mem framework[1]
[1]https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git/log/?h=for-4.18