[PATCH v2 3/3] ata: ahci: implement SCSI_SYNC_CACHE

[Neil Armstrong]

On 26/03/2025 13:24, Caleb Connolly wrote:
> The SCSI layer now issues a SYNC_CACHE command after every write to
> ensure there is no data loss due to a board reset after write.
> 
> Implement support for this command and remove the same logic from the
> ATA write path to be consistent with other SCSI backends.
> 
> Ranges are not supported and the whole cache will be flushed in all
> cases.
> 
> This was done per iteration in ata_scsiop_read_write(), but it's not
> clear why this was the case, calling it once for the entire write ought
> to achieve the same result.
> 
> Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
> ---
>   drivers/ata/ahci.c | 14 +++-----------
>   1 file changed, 3 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 8058d5ff1c37f92914f250fa9cc78498a3f27331..deb91efd6d2666016f375feabb16ebc8f68fb697 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -735,19 +735,8 @@ static int ata_scsiop_read_write(struct ahci_uc_priv *uc_priv,
>   			debug("scsi_ahci: SCSI %s10 command failure.\n",
>   			      is_write ? "WRITE" : "READ");
>   			return -EIO;
>   		}
> -
> -		/* If this transaction is a write, do a following flush.
> -		 * Writes in u-boot are so rare, and the logic to know when is
> -		 * the last write and do a flush only there is sufficiently
> -		 * difficult. Just do a flush after every write. This incurs,
> -		 * usually, one extra flush when the rare writes do happen.
> -		 */
> -		if (is_write) {
> -			if (-EIO == ata_io_flush(uc_priv, pccb->target))
> -				return -EIO;
> -		}
>   		user_buffer += transfer_size;
>   		user_buffer_size -= transfer_size;
>   		blocks -= now_blocks;
>   		lba += now_blocks;
> @@ -845,8 +834,11 @@ static int ahci_scsi_exec(struct udevice *dev, struct scsi_cmd *pccb)
>   		break;
>   	case SCSI_INQUIRY:
>   		ret = ata_scsiop_inquiry(uc_priv, pccb);
>   		break;
> +	case SCSI_SYNC_CACHE:
> +		ret = ata_io_flush(uc_priv, pccb->target);
> +		break;
>   	default:
>   		printf("Unsupport SCSI command 0x%02x\n", pccb->cmd[0]);
>   		return -ENOTSUPP;
>   	}
> 

Good catch, much simpler to move it in the scsi layer !

Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>

Can someone test on a SATA enabled device ?

I can have a test run on the Odroid-HC4 with a PCIe-SATA controller.

Thanks,
Neil