sata_mv fix mv_host_intr bug for hc_irq_cause

Remove the unwanted reads of hc_irq_cause from mv_host_intr(),
thereby removing a bug whereby we were not always reading it when needed..
Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_mv.c

@@ -1818,48 +1818,61 @@ static void mv_process_crpb_entries(struct ata_port *ap, struct mv_port_priv *pp
 static int mv_host_intr(struct ata_host *host, u32 main_irq_cause)
 {
 	struct mv_host_priv *hpriv = host->private_data;
-	void __iomem *mmio = hpriv->base, *hc_mmio = NULL;
-	u32 hc_irq_cause = 0;
+	void __iomem *mmio = hpriv->base, *hc_mmio;
 	unsigned int handled = 0, port;
 
 	for (port = 0; port < hpriv->n_ports; port++) {
 		struct ata_port *ap = host->ports[port];
 		struct mv_port_priv *pp;
-		unsigned int shift, hardport, port_cause;
+		unsigned int p, shift, hardport, port_cause;
+
+		MV_PORT_TO_SHIFT_AND_HARDPORT(port, shift, hardport);
 		/*
-		 * When we move to the second hc, flag our cached
-		 * copies of hc_mmio (and hc_irq_cause) as invalid again.
+		 * Each hc within the host has its own hc_irq_cause register,
+		 * where the interrupting ports bits get ack'd.
 		 */
-		if (port == MV_PORTS_PER_HC)
-			hc_mmio = NULL;
+		if (hardport == 0) {	/* first port on this hc ? */
+			u32 hc_cause = (main_irq_cause >> shift) & HC0_IRQ_PEND;
+			u32 port_mask, ack_irqs;
 			/*
-		 * Do nothing if port is not interrupting or is disabled:
+			 * Skip this entire hc if nothing pending for any ports
 			 */
-		MV_PORT_TO_SHIFT_AND_HARDPORT(port, shift, hardport);
-		port_cause = (main_irq_cause >> shift) & (DONE_IRQ | ERR_IRQ);
-		if (!port_cause || !ap || (ap->flags & ATA_FLAG_DISABLED))
+			if (!hc_cause) {
+				port += MV_PORTS_PER_HC - 1;
 				continue;
+			}
 			/*
-		 * Each hc within the host has its own hc_irq_cause register.
-		 * We defer reading it until we know we need it, right now:
+			 * We don't need/want to read the hc_irq_cause register,
+			 * because doing so hurts performance, and
+			 * main_irq_cause already gives us everything we need.
+			 *
+			 * But we do have to *write* to the hc_irq_cause to ack
+			 * the ports that we are handling this time through.
 			 *
-		 * FIXME later: we don't really need to read this register
-		 * (some logic changes required below if we go that way),
-		 * because it doesn't tell us anything new.  But we do need
-		 * to write to it, outside the top of this loop,
-		 * to reset the interrupt triggers for next time.
+			 * This requires that we create a bitmap for those
+			 * ports which interrupted us, and use that bitmap
+			 * to ack (only) those ports via hc_irq_cause.
 			 */
-		if (!hc_mmio) {
+			ack_irqs = 0;
+			for (p = 0; p < MV_PORTS_PER_HC; ++p) {
+				if ((port + p) >= hpriv->n_ports)
+					break;
+				port_mask = (DONE_IRQ | ERR_IRQ) << (p * 2);
+				if (hc_cause & port_mask)
+					ack_irqs |= (DMA_IRQ | DEV_IRQ) << p;
+			}
 			hc_mmio = mv_hc_base_from_port(mmio, port);
-			hc_irq_cause = readl(hc_mmio + HC_IRQ_CAUSE_OFS);
-			writelfl(~hc_irq_cause, hc_mmio + HC_IRQ_CAUSE_OFS);
+			writelfl(~ack_irqs, hc_mmio + HC_IRQ_CAUSE_OFS);
 			handled = 1;
 		}
+		port_cause = (main_irq_cause >> shift) & (DONE_IRQ | ERR_IRQ);
+		if (!port_cause)
+			continue;
 		/*
 		 * Process completed CRPB response(s) before other events.
 		 */
 		pp = ap->private_data;
-		if (hc_irq_cause & (DMA_IRQ << hardport)) {
+		if (port_cause & DONE_IRQ) {
 			if (pp->pp_flags & MV_PP_FLAG_EDMA_EN)
 				mv_process_crpb_entries(ap, pp);
 		}
@@ -1868,17 +1881,17 @@ static int mv_host_intr(struct ata_host *host, u32 main_irq_cause)
 		 */
 		if (unlikely(port_cause & ERR_IRQ)) {
 			mv_err_intr(ap);
-		} else if (hc_irq_cause & (DEV_IRQ << hardport)) {
+		} else {
 			if (!(pp->pp_flags & MV_PP_FLAG_EDMA_EN)) {
 				struct ata_queued_cmd *qc = mv_get_active_qc(ap);
 				if (qc) {
 					ata_sff_host_intr(ap, qc);
 					continue;
 				}
-			}
 				mv_unexpected_intr(ap);
 			}
 		}
+	}
 	return handled;
 }