From: Sanjaikumar V S <sanjaikumar.vs@dicortech.com>

When writing to SST flash starting at an odd address, a single byte is
first programmed using the byte program (BP) command. After this
operation completes, the flash hardware automatically clears the Write
Enable Latch (WEL) bit.

If an AAI (Auto Address Increment) word program sequence follows, it
requires WEL to be set. Without re-enabling writes, the AAI sequence
fails.

Add spi_nor_write_enable() after the odd-address byte program when more
data needs to be written. Use a local boolean for clarity.

Fixes: b199489d37b2 ("mtd: spi-nor: add the framework for SPI NOR")
Cc: stable@vger.kernel.org
Signed-off-by: Sanjaikumar V S <sanjaikumar.vs@dicortech.com>
---
 drivers/mtd/spi-nor/sst.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
index 175211fe6a5e..db02c14ba16f 100644
--- a/drivers/mtd/spi-nor/sst.c
+++ b/drivers/mtd/spi-nor/sst.c
@@ -203,6 +203,8 @@ static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 	/* Start write from odd address. */
 	if (to % 2) {
+		bool needs_write_enable = (len > 1);
+
 		/* write one byte. */
 		ret = sst_nor_write_data(nor, to, 1, buf);
 		if (ret < 0)
@@ -210,6 +212,17 @@ static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 		to++;
 		actual++;
+
+		/*
+		 * Byte program clears the write enable latch. If more
+		 * data needs to be written using the AAI sequence,
+		 * re-enable writes.
+		 */
+		if (needs_write_enable) {
+			ret = spi_nor_write_enable(nor);
+			if (ret)
+				goto out;
+		}
 	}
 
 	/* Write out most of the data here. */
-- 
2.43.0

On Wed, Mar 11 2026, Sanjaikumar V S wrote:

> From: Sanjaikumar V S <sanjaikumar.vs@dicortech.com>
>
> When writing to SST flash starting at an odd address, a single byte is
> first programmed using the byte program (BP) command. After this
> operation completes, the flash hardware automatically clears the Write
> Enable Latch (WEL) bit.
>
> If an AAI (Auto Address Increment) word program sequence follows, it
> requires WEL to be set. Without re-enabling writes, the AAI sequence
> fails.
>
> Add spi_nor_write_enable() after the odd-address byte program when more
> data needs to be written. Use a local boolean for clarity.
>
> Fixes: b199489d37b2 ("mtd: spi-nor: add the framework for SPI NOR")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sanjaikumar V S <sanjaikumar.vs@dicortech.com>

Acked-by: Pratyush Yadav <pratyush@kernel.org>

[...]

-- 
Regards,
Pratyush Yadav

Hello,

On 3/11/26 11:30, Sanjaikumar V S wrote:
> From: Sanjaikumar V S <sanjaikumar.vs@dicortech.com>
> 
> When writing to SST flash starting at an odd address, a single byte is
> first programmed using the byte program (BP) command. After this
> operation completes, the flash hardware automatically clears the Write
> Enable Latch (WEL) bit.
> 
> If an AAI (Auto Address Increment) word program sequence follows, it
> requires WEL to be set. Without re-enabling writes, the AAI sequence
> fails.
> 
> Add spi_nor_write_enable() after the odd-address byte program when more
> data needs to be written. Use a local boolean for clarity.
> 
> Fixes: b199489d37b2 ("mtd: spi-nor: add the framework for SPI NOR")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sanjaikumar V S <sanjaikumar.vs@dicortech.com>
> ---
>   drivers/mtd/spi-nor/sst.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
> index 175211fe6a5e..db02c14ba16f 100644
> --- a/drivers/mtd/spi-nor/sst.c
> +++ b/drivers/mtd/spi-nor/sst.c
> @@ -203,6 +203,8 @@ static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
>   
>   	/* Start write from odd address. */
>   	if (to % 2) {
> +		bool needs_write_enable = (len > 1);
> +
>   		/* write one byte. */
>   		ret = sst_nor_write_data(nor, to, 1, buf);
>   		if (ret < 0)
> @@ -210,6 +212,17 @@ static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
>   
>   		to++;
>   		actual++;
> +
> +		/*
> +		 * Byte program clears the write enable latch. If more
> +		 * data needs to be written using the AAI sequence,
> +		 * re-enable writes.
> +		 */
> +		if (needs_write_enable) {
> +			ret = spi_nor_write_enable(nor);
> +			if (ret)
> +				goto out;
> +		}
>   	}
>   
>   	/* Write out most of the data here. */

found a board with

   spi-nor spi0.0: sst25vf032b (4096 Kbytes)

for testing. Tests are on top of

   94645aa41bf9e (mtd/spi-nor/next)

This should be done according to the datasheet and fixes that only 1
byte is written on writes to a an odd address and following AAI writes
fail, resulting in something looking like this:

ffa9 ffff ffff ffff ffff ffff ffff ffff

when

24a9 91b3 7cb6 f01c 2994 c368 fdad d3a2

was supposed to be written.

Tested-by: Hendrik Donner <hd@os-cillation.de>
Reviewed-by: Hendrik Donner <hd@os-cillation.de>

Regards,
Hendrik