scsi: ufs: core: Set the Command Priority (CP) flag for RT requests

Make the UFS device execute realtime (RT) requests before other requests.
This will be used in Android to reduce the I/O latency of the foreground
app.

Note: UFS devices do not support CDL so using CDL is not a viable
alternative.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230921192335.676924-5-bvanassche@acm.org
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 13957ca8055b12ac34791f53d7e07940b3222a7c..d430e2e7fb390068d410eaf97a83ed5c3d7741dd 100644 (file)
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -2717,6 +2717,8 @@ static int ufshcd_compose_devman_upiu(struct ufs_hba *hba,
  */
 static void ufshcd_comp_scsi_upiu(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
 {
+       struct request *rq = scsi_cmd_to_rq(lrbp->cmd);
+       unsigned int ioprio_class = IOPRIO_PRIO_CLASS(req_get_ioprio(rq));
        u8 upiu_flags;
 
        if (hba->ufs_version <= ufshci_version(1, 1))
@@ -2726,6 +2728,8 @@ static void ufshcd_comp_scsi_upiu(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
 
        ufshcd_prepare_req_desc_hdr(lrbp, &upiu_flags,
                                    lrbp->cmd->sc_data_direction, 0);
+       if (ioprio_class == IOPRIO_CLASS_RT)
+               upiu_flags |= UPIU_CMD_FLAGS_CP;
        ufshcd_prepare_utp_scsi_cmd_upiu(lrbp, upiu_flags);
 }
 

diff --git a/include/ufs/ufs.h b/include/ufs/ufs.h
index 0cced88f4531e87384ab676d1c01149ccb4ef36b..e77ab17868569be73e7bceb44fc5defbb58aea1c 100644 (file)
--- a/include/ufs/ufs.h
+++ b/include/ufs/ufs.h
@@ -98,9 +98,10 @@ enum upiu_response_transaction {
        UPIU_TRANSACTION_REJECT_UPIU    = 0x3F,
 };
 
-/* UPIU Read/Write flags */
+/* UPIU Read/Write flags. See also table "UPIU Flags" in the UFS standard. */
 enum {
        UPIU_CMD_FLAGS_NONE     = 0x00,
+       UPIU_CMD_FLAGS_CP       = 0x04,
        UPIU_CMD_FLAGS_WRITE    = 0x20,
        UPIU_CMD_FLAGS_READ     = 0x40,
 };