sata_mv: leave SError bits untouched in mv_err_intr

Here it is again, minus the checkpatch.pl complaint:

Rework mv_err_intr() to leave the SError bits as-is,
so that libata-eh has a chance to see/use them.

We originally thought that clearing them here was necessary
before writing back to edma_err_cause (per the Marvell datasheets),
but we will end up reseting the chip regardless in those cases.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_mv.c

@@ -1523,13 +1523,11 @@ static void mv_unexpected_intr(struct ata_port *ap)
 /**
  *      mv_err_intr - Handle error interrupts on the port
  *      @ap: ATA channel to manipulate
- *      @reset_allowed: bool: 0 == don't trigger from reset here
+ *      @qc: affected command (non-NCQ), or NULL
  *
- *      In most cases, just clear the interrupt and move on.  However,
- *      some cases require an eDMA reset, which also performs a COMRESET.
- *      The SERR case requires a clear of pending errors in the SATA
- *      SERROR register.  Finally, if the port disabled DMA,
- *      update our cached copy to match.
+ *      Most cases require a full reset of the chip's state machine,
+ *      which also performs a COMRESET.
+ *      Also, if the port disabled DMA, update our cached copy to match.
  *
  *      LOCKING:
  *      Inherited from caller.
@@ -1540,21 +1538,18 @@ static void mv_err_intr(struct ata_port *ap, struct ata_queued_cmd *qc)
 	u32 edma_err_cause, eh_freeze_mask, serr = 0;
 	struct mv_port_priv *pp = ap->private_data;
 	struct mv_host_priv *hpriv = ap->host->private_data;
-	unsigned int edma_enabled = (pp->pp_flags & MV_PP_FLAG_EDMA_EN);
 	unsigned int action = 0, err_mask = 0;
 	struct ata_eh_info *ehi = &ap->link.eh_info;
 
 	ata_ehi_clear_desc(ehi);
 
-	if (!edma_enabled) {
-		/* just a guess: do we need to do this? should we
-		 * expand this, and do it in all cases?
-		 */
-		sata_scr_read(&ap->link, SCR_ERROR, &serr);
-		sata_scr_write_flush(&ap->link, SCR_ERROR, serr);
-	}
-
+	/*
+	 * Read and clear the err_cause bits.  This won't actually
+	 * clear for some errors (eg. SError), but we will be doing
+	 * a hard reset in those cases regardless, which *will* clear it.
+	 */
 	edma_err_cause = readl(port_mmio + EDMA_ERR_IRQ_CAUSE_OFS);
+	writelfl(~edma_err_cause, port_mmio + EDMA_ERR_IRQ_CAUSE_OFS);
 
 	ata_ehi_push_desc(ehi, "edma_err_cause=%08x", edma_err_cause);
 
@@ -1594,16 +1589,19 @@ static void mv_err_intr(struct ata_port *ap, struct ata_queued_cmd *qc)
 			ata_ehi_push_desc(ehi, "EDMA self-disable");
 		}
 		if (edma_err_cause & EDMA_ERR_SERR) {
-			sata_scr_read(&ap->link, SCR_ERROR, &serr);
-			sata_scr_write_flush(&ap->link, SCR_ERROR, serr);
-			err_mask = AC_ERR_ATA_BUS;
+			/*
+			 * Ensure that we read our own SCR, not a pmp link SCR:
+			 */
+			ap->ops->scr_read(ap, SCR_ERROR, &serr);
+			/*
+			 * Don't clear SError here; leave it for libata-eh:
+			 */
+			ata_ehi_push_desc(ehi, "SError=%08x", serr);
+			err_mask |= AC_ERR_ATA_BUS;
 			action |= ATA_EH_RESET;
 		}
 	}
 
-	/* Clear EDMA now that SERR cleanup done */
-	writelfl(~edma_err_cause, port_mmio + EDMA_ERR_IRQ_CAUSE_OFS);
-
 	if (!err_mask) {
 		err_mask = AC_ERR_OTHER;
 		action |= ATA_EH_RESET;