[PATCH v2 2/3] scsi: ufs: core: Tolerate RX_FOM read failures in TX EQTR

[Can Guo <can.guo@oss.qualcomm.com>]

ufshcd_get_rx_fom() aborted TX EQTR when a per-lane RX_FOM DME read failed.
That makes the whole training flow fragile even though these reads can be
treated as best effort.

Keep TX EQTR running by logging RX_FOM read failures and continuing.
Make failed lanes deterministic by initializing each lane FOM to 0 before
reading and only updating it when the DME read succeeds. This avoids
propagating stale or uninitialized values into EQTR evaluation.

Also update the kerneldoc return description to match behavior: RX_FOM
DME read failures are handled as warnings, while get_rx_fom() vops
failures are still propagated to the caller.

Signed-off-by: Can Guo <can.guo@oss.qualcomm.com>
---
 drivers/ufs/core/ufs-txeq.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/ufs/core/ufs-txeq.c b/drivers/ufs/core/ufs-txeq.c
index 9dca0cd344b8..e1302ea9f27e 100644
--- a/drivers/ufs/core/ufs-txeq.c
+++ b/drivers/ufs/core/ufs-txeq.c
@@ -482,7 +482,8 @@ static void ufshcd_evaluate_tx_eqtr_fom(struct ufs_hba *hba,
  * @h_iter: host TX EQTR iterator data structure
  * @d_iter: device TX EQTR iterator data structure
  *
- * Returns 0 on success, negative error code otherwise
+ * Returns 0 on success, negative error code if get_rx_fom vops fails.
+ * RX_FOM DME get failures are logged and treated as 0 FOM for that lane.
  */
 static int ufshcd_get_rx_fom(struct ufs_hba *hba,
 			     struct ufs_pa_layer_attr *pwr_mode,
@@ -497,8 +498,12 @@ static int ufshcd_get_rx_fom(struct ufs_hba *hba,
 		ret = ufshcd_dme_peer_get(hba, UIC_ARG_MIB_SEL(RX_FOM,
 					  UIC_ARG_MPHY_RX_GEN_SEL_INDEX(lane)),
 					  &fom);
-		if (ret)
-			return ret;
+		if (ret) {
+			h_iter->fom[lane] = 0;
+			dev_dbg(hba->dev, "Failed to get FOM for Host TX Lane %d: %d\n",
+				 lane, ret);
+			continue;
+		}
 
 		h_iter->fom[lane] = (u8)fom;
 	}
@@ -508,8 +513,12 @@ static int ufshcd_get_rx_fom(struct ufs_hba *hba,
 		ret = ufshcd_dme_get(hba, UIC_ARG_MIB_SEL(RX_FOM,
 				     UIC_ARG_MPHY_RX_GEN_SEL_INDEX(lane)),
 				     &fom);
-		if (ret)
-			return ret;
+		if (ret) {
+			d_iter->fom[lane] = 0;
+			dev_dbg(hba->dev, "Failed to get FOM for Device TX Lane %d: %d\n",
+				 lane, ret);
+			continue;
+		}
 
 		d_iter->fom[lane] = (u8)fom;
 	}
-- 
2.34.1