[PATCH v1] scsi: Enable FUA bit and remove per-write SYNC_CACHE operations

[Varadarajan Narayanan]

On Mon, Jan 05, 2026 at 10:55:26AM +0530, Balaji Selvanathan wrote:
> Enable the Force Unit Access (FUA) bit in SCSI WRITE10 commands to
> ensure writes bypass the device's volatile cache and go directly to
> non-volatile storage. This provides write-through behavior without
> requiring explicit cache flushes after each write operation.
>
> Remove the SYNC_CACHE command that was being issued after every
> scsi_write() call, as it is redundant when FUA is enabled and was
> causing system hangs during large sparse image flashing operations.
>
> Signed-off-by: Aswin Murugan <aswin.murugan at oss.qualcomm.com>
> Signed-off-by: Balaji Selvanathan <balaji.selvanathan at oss.qualcomm.com>

Reviewed-by: Varadarajan Narayanan <varadarajan.narayanan at oss.qualcomm.com>

> ---
>  drivers/scsi/scsi.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 8fe6b38a8c7..b755616bf3f 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -124,7 +124,7 @@ static void scsi_setup_write_ext(struct scsi_cmd *pccb, lbaint_t start,
>  				 lbaint_t blocks)
>  {
>  	pccb->cmd[0] = SCSI_WRITE10;
> -	pccb->cmd[1] = 0;
> +	pccb->cmd[1] = 0x08; /* Set FUA bit to bypass write cache */
>  	pccb->cmd[2] = (unsigned char)(start >> 24) & 0xff;
>  	pccb->cmd[3] = (unsigned char)(start >> 16) & 0xff;
>  	pccb->cmd[4] = (unsigned char)(start >> 8) & 0xff;
> @@ -301,11 +301,6 @@ static ulong scsi_write(struct udevice *dev, lbaint_t blknr, lbaint_t blkcnt,
>  		buf_addr += pccb->datalen;
>  	} while (blks != 0);
>
> -	/* Flush the SCSI cache so we don't lose data on board reset. */
> -	scsi_setup_sync_cache(pccb, 0, 0);
> -	if (scsi_exec(bdev, pccb))
> -		scsi_print_error(pccb);
> -
>  	debug("%s: end startblk " LBAF ", blccnt " LBAF " buffer %lX\n",
>  	      __func__, start, blocks, buf_addr);
>  	return blkcnt;
> --
> 2.34.1
>