[PATCH v2 1/2] scsi: ufs: Fix residual handling

[Bart Van Assche <bvanassche@acm.org>]

Only call scsi_set_resid() in case of an underflow. Do not call
scsi_set_resid() in case of an overflow.

Cc: Avri Altman <avri.altman@wdc.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Fixes: cb38845d90fc ("scsi: ufs: core: Set the residual byte count")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/ufs/core/ufshcd.c | 12 ++++++++++--
 include/ufs/ufs.h         |  6 ++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index c394dc50504a..27e1a4914837 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -5222,9 +5222,17 @@ ufshcd_transfer_rsp_status(struct ufs_hba *hba, struct ufshcd_lrb *lrbp,
 	int result = 0;
 	int scsi_status;
 	enum utp_ocs ocs;
+	u8 upiu_flags;
+	u32 resid;
 
-	scsi_set_resid(lrbp->cmd,
-		be32_to_cpu(lrbp->ucd_rsp_ptr->sr.residual_transfer_count));
+	upiu_flags = be32_to_cpu(lrbp->ucd_rsp_ptr->header.dword_0) >> 16;
+	resid = be32_to_cpu(lrbp->ucd_rsp_ptr->sr.residual_transfer_count);
+	/*
+	 * Test !overflow instead of underflow to support UFS devices that do
+	 * not set either flag.
+	 */
+	if (resid && !(upiu_flags & UPIU_RSP_FLAG_OVERFLOW))
+		scsi_set_resid(lrbp->cmd, resid);
 
 	/* overall command status of utrd */
 	ocs = ufshcd_get_tr_ocs(lrbp, cqe);
diff --git a/include/ufs/ufs.h b/include/ufs/ufs.h
index 0dd546a20503..c789252b5fad 100644
--- a/include/ufs/ufs.h
+++ b/include/ufs/ufs.h
@@ -104,6 +104,12 @@ enum {
 	UPIU_CMD_FLAGS_READ	= 0x40,
 };
 
+/* UPIU response flags */
+enum {
+	UPIU_RSP_FLAG_UNDERFLOW	= 0x20,
+	UPIU_RSP_FLAG_OVERFLOW	= 0x40,
+};
+
 /* UPIU Task Attributes */
 enum {
 	UPIU_TASK_ATTR_SIMPLE	= 0x00,