Command Processing 3. After fetching the Entry, Host Controller updates SQ doorbell head pointer 4. Host controller sends COMMAND UPIU to UFS device" In other words, for both legacy and MCQ mode, UFS controllers are required to forward commands to the UFS device in the order these commands have been received from the host. Notes: - For legacy mode this is only correct if the host submits one command at a time. The UFS driver does this. - Also in legacy mode, the command order is not preserved if auto-hibernation is enabled in the UFS controller. This patch improves performance as follows on a test setup with UFSHCI 3.0 controller: - With the mq-deadline scheduler: 2.5x more IOPS for small writes. - When not using an I/O scheduler compared to using mq-deadline with zone locking: 4x more IOPS for small writes. Cc: Bao D. Nguyen <quic_nguyenb@xxxxxxxxxxx> Cc: Can Guo <quic_cang@xxxxxxxxxxx> Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Cc: Avri Altman <avri.altman@xxxxxxx> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx> --- drivers/ufs/core/ufshcd.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index abbe7135a977..a6dec3b7e3fd 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -5241,6 +5241,13 @@ static int ufshcd_device_configure(struct scsi_dev= ice *sdev, struct ufs_hba *hba =3D shost_priv(sdev->host); struct request_queue *q =3D sdev->request_queue; =20 + /* + * With auto-hibernation disabled, the write order is preserved per + * MCQ. Auto-hibernation may cause write reordering that results in + * unaligned write errors. The SCSI core will retry the failed writes. + */ + lim->driver_preserves_write_order =3D true; + lim->dma_pad_mask =3D PRDT_DATA_BYTE_COUNT_PAD - 1; =20 /*
