[PATCH] mtd: spi-nor: sst: Fix SST write failure

[Pratyush Yadav]

Hi Amit,

On Thu, Feb 13 2025, Amit Kumar Mahapatra wrote:

> 'commit 18bcb4aa54ea ("mtd: spi-nor: sst: Factor out common write operation
> to `sst_nor_write_data()`")' introduced a bug where only one byte of data
> is written, regardless of the number of bytes passed to
> sst_nor_write_data(), causing a kernel crash during the write operation.

Does it crash or only cause a warning? This comes from a WARN() so it
should not crash the kernel unless you set panic_on_warn.

> Ensure the correct number of bytes are written as passed to
> sst_nor_write_data().
>
> Call trace:
> [   57.400180] ------------[ cut here ]------------
> [   57.404842] While writing 2 byte written 1 bytes
> [   57.409493] WARNING: CPU: 0 PID: 737 at drivers/mtd/spi-nor/sst.c:187 sst_nor_write_data+0x6c/0x74
> [   57.418464] Modules linked in:
> [   57.421517] CPU: 0 UID: 0 PID: 737 Comm: mtd_debug Not tainted 6.12.0-g5ad04afd91f9 #30
> [   57.429517] Hardware name: Xilinx Versal A2197 Processor board revA - x-prc-02 revA (DT)
> [   57.437600] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   57.444557] pc : sst_nor_write_data+0x6c/0x74
> [   57.448911] lr : sst_nor_write_data+0x6c/0x74
> [   57.453264] sp : ffff80008232bb40
> [   57.456570] x29: ffff80008232bb40 x28: 0000000000010000 x27: 0000000000000001
> [   57.463708] x26: 000000000000ffff x25: 0000000000000000 x24: 0000000000000000
> [   57.470843] x23: 0000000000010000 x22: ffff80008232bbf0 x21: ffff000816230000
> [   57.477978] x20: ffff0008056c0080 x19: 0000000000000002 x18: 0000000000000006
> [   57.485112] x17: 0000000000000000 x16: 0000000000000000 x15: ffff80008232b580
> [   57.492246] x14: 0000000000000000 x13: ffff8000816d1530 x12: 00000000000004a4
> [   57.499380] x11: 000000000000018c x10: ffff8000816fd530 x9 : ffff8000816d1530
> [   57.506515] x8 : 00000000fffff7ff x7 : ffff8000816fd530 x6 : 0000000000000001
> [   57.513649] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
> [   57.520782] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0008049b0000
> [   57.527916] Call trace:
> [   57.530354]  sst_nor_write_data+0x6c/0x74
> [   57.534361]  sst_nor_write+0xb4/0x18c
> [   57.538019]  mtd_write_oob_std+0x7c/0x88
> [   57.541941]  mtd_write_oob+0x70/0xbc
> [   57.545511]  mtd_write+0x68/0xa8
> [   57.548733]  mtdchar_write+0x10c/0x290
> [   57.552477]  vfs_write+0xb4/0x3a8
> [   57.555791]  ksys_write+0x74/0x10c
> [   57.559189]  __arm64_sys_write+0x1c/0x28
> [   57.563109]  invoke_syscall+0x54/0x11c
> [   57.566856]  el0_svc_common.constprop.0+0xc0/0xe0
> [   57.571557]  do_el0_svc+0x1c/0x28
> [   57.574868]  el0_svc+0x30/0xcc
> [   57.577921]  el0t_64_sync_handler+0x120/0x12c
> [   57.582276]  el0t_64_sync+0x190/0x194
> [   57.585933] ---[ end trace 0000000000000000 ]---
>
> Fixes: 18bcb4aa54ea ("mtd: spi-nor: sst: Factor out common write operation to `sst_nor_write_data()`")
> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra at amd.com>
> ---
> BRANCH: mtd/next
> ---
>  drivers/mtd/spi-nor/sst.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
> index b5ad7118c49a..175211fe6a5e 100644
> --- a/drivers/mtd/spi-nor/sst.c
> +++ b/drivers/mtd/spi-nor/sst.c
> @@ -174,7 +174,7 @@ static int sst_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
>  	int ret;
>  
>  	nor->program_opcode = op;
> -	ret = spi_nor_write_data(nor, to, 1, buf);
> +	ret = spi_nor_write_data(nor, to, len, buf);

What a silly bug! Thanks for fixing it. I will let the patch sit on the
list for a couple days to get some eyes on it and then will apply it.

Reviewed-by: Pratyush Yadav <pratyush at kernel.org>

>  	if (ret < 0)
>  		return ret;
>  	WARN(ret != len, "While writing %zu byte written %i bytes\n", len, ret);

-- 
Regards,
Pratyush Yadav