From 880c87d7846607657aa4c91daa1e2d5345bba93f Mon Sep 17 00:00:00 2001 From: Sanjaikumar V S Date: Fri, 8 May 2026 19:59:24 -0400 Subject: [PATCH] mtd: spi-nor: sst: Fix write enable before AAI sequence [ Upstream commit a0f64241d3566a49c0a9b33ba7ae458ae22003a9 ] 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 Tested-by: Hendrik Donner Reviewed-by: Hendrik Donner Signed-off-by: Pratyush Yadav (Google) [ kept inline `nor->program_opcode = SPINOR_OP_BP;` ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman [uli: backport to 4.19] Signed-off-by: Ulrich Hecht Reviewed-by: Pavel Machek --- drivers/mtd/spi-nor/spi-nor.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index ff641c06003a..1e55d9ccaab4 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -1350,6 +1350,8 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len, actual = to % 2; /* Start write from odd address. */ if (actual) { + bool needs_write_enable = (len > 1); + nor->program_opcode = SPINOR_OP_BP; /* write one byte. */ @@ -1361,6 +1363,17 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len, ret = spi_nor_wait_till_ready(nor); if (ret) goto sst_write_err; + + /* + * 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 = write_enable(nor); + if (ret) + goto sst_write_err; + } } to += actual;