[U-Boot] [PATCH] mtd: spi: Improve data write functionality

[Rajat Srivastava]

Incorporate write enable and status check in the write data
function itself.

Formerly, Write data function used to break the data to be
written into smaller chunks and used to send the smaller
chunks without write enable or status check for every iteration.

Signed-off-by: Rajat Srivastava <rajat.srivastava at nxp.com>
---
While writing any data to a SPI flash every write transaction
shall be preceded by a WRITE_ENABLE command and shall be
followed by a READ_STATUS process (to check if the flash is
not busy).
This sequence can be roughly represented as:
1. write_enable  //issue write enable command
2. execute_write_operation  //write data to flash or register
3. spi_nor_wait_till_ready  //read status of flash
 
The current framework has two types of write operation:
1. write to register (nor->write_reg)
2. write data to flash memory (nor->write)
 
There seems to be an issue in writing data to flash memory for which
the framework uses spi_nor_write_data() function.
Before every call to spi_nor_write_data() function the framework
sends a WRITE_ENABLE command and later checks if the flash is busy.
However, the spi_nor_write_data() function which executes the data
write to flash, breaks the data into smaller chunks. For all of
these small transactions there is only a single WRITE_ENABLE
command issued and a single check made for status, which breaks
the write operation. Only the first chunk of the whole data is
successfully written on to the flash.

This patch fixes the bug making the spi_nor_write_data() function
issue WRITE_ENABLE command and status checks with every write
transactions.

Without this patch write in fsl_qspi.c driver is broken.

 drivers/mtd/spi/spi-nor-core.c | 30 +++++++++---------------------
 1 file changed, 9 insertions(+), 21 deletions(-)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index c4e2f6a08f..757163369b 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -23,6 +23,9 @@
 
 #include "sf_internal.h"
 
+static int spi_nor_wait_till_ready(struct spi_nor *nor);
+static int write_enable(struct spi_nor *nor);
+
 /* Define max times to check status register before we give up. */
 
 /*
@@ -128,6 +131,8 @@ static ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
 		op.addr.nbytes = 0;
 
 	while (remaining) {
+		write_enable(nor);
+
 		op.data.nbytes = remaining < UINT_MAX ? remaining : UINT_MAX;
 		ret = spi_mem_adjust_op_size(nor->spi, &op);
 		if (ret)
@@ -137,6 +142,10 @@ static ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
 		if (ret)
 			return ret;
 
+		ret = spi_nor_wait_till_ready(nor);
+		if (ret)
+			return ret;
+
 		op.addr.val += op.data.nbytes;
 		remaining -= op.data.nbytes;
 		op.data.buf.out += op.data.nbytes;
@@ -961,14 +970,10 @@ static int sst_write_byteprogram(struct spi_nor *nor, loff_t to, size_t len,
 	for (actual = 0; actual < len; actual++) {
 		nor->program_opcode = SPINOR_OP_BP;
 
-		write_enable(nor);
 		/* write one byte. */
 		ret = nor->write(nor, to, 1, buf + actual);
 		if (ret < 0)
 			goto sst_write_err;
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto sst_write_err;
 		to++;
 	}
 
@@ -989,8 +994,6 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
 	if (spi->mode & SPI_TX_BYTE)
 		return sst_write_byteprogram(nor, to, len, retlen, buf);
 
-	write_enable(nor);
-
 	nor->sst_write_second = false;
 
 	actual = to % 2;
@@ -1002,9 +1005,6 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
 		ret = nor->write(nor, to, 1, buf);
 		if (ret < 0)
 			goto sst_write_err;
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto sst_write_err;
 	}
 	to += actual;
 
@@ -1016,9 +1016,6 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
 		ret = nor->write(nor, to, 2, buf + actual);
 		if (ret < 0)
 			goto sst_write_err;
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto sst_write_err;
 		to += 2;
 		nor->sst_write_second = true;
 	}
@@ -1031,15 +1028,10 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 	/* Write out trailing byte if it exists. */
 	if (actual != len) {
-		write_enable(nor);
-
 		nor->program_opcode = SPINOR_OP_BP;
 		ret = nor->write(nor, to, 1, buf + actual);
 		if (ret < 0)
 			goto sst_write_err;
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto sst_write_err;
 		write_disable(nor);
 		actual += 1;
 	}
@@ -1090,15 +1082,11 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 		if (ret < 0)
 			return ret;
 #endif
-		write_enable(nor);
 		ret = nor->write(nor, addr, page_remain, buf + i);
 		if (ret < 0)
 			goto write_err;
 		written = ret;
 
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto write_err;
 		*retlen += written;
 		i += written;
 		if (written != page_remain) {
-- 
2.17.1