ata_piix: drop merged SCR access and use slave_link instead

Now that libata has slave_link, there's no need to keep ugly merged
SCR access.  Drop it and use slave_link instead.  This results in
simpler code and much better separate link handling for master and
slave.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/ata_piix.c

@@ -887,23 +887,9 @@ static void ich_set_dmamode(struct ata_port *ap, struct ata_device *adev)
  * Serial ATA Index/Data Pair Superset Registers access
  *
  * Beginning from ICH8, there's a sane way to access SCRs using index
- * and data register pair located at BAR5.  This creates an
- * interesting problem of mapping two SCRs to one port.
- *
- * Although they have separate SCRs, the master and slave aren't
- * independent enough to be treated as separate links - e.g. softreset
- * resets both.  Also, there's no protocol defined for hard resetting
- * singled device sharing the virtual port (no defined way to acquire
- * device signature).  This is worked around by merging the SCR values
- * into one sensible value and requesting follow-up SRST after
- * hardreset.
- *
- * SCR merging is perfomed in nibbles which is the unit contents in
- * SCRs are organized.  If two values are equal, the value is used.
- * When they differ, merge table which lists precedence of possible
- * values is consulted and the first match or the last entry when
- * nothing matches is used.  When there's no merge table for the
- * specific nibble, value from the first port is used.
+ * and data register pair located at BAR5 which means that we have
+ * separate SCRs for master and slave.  This is handled using libata
+ * slave_link facility.
  */
 static const int piix_sidx_map[] = {
 	[SCR_STATUS]	= 0,
@@ -911,125 +897,38 @@ static const int piix_sidx_map[] = {
 	[SCR_CONTROL]	= 1,
 };
 
-static void piix_sidpr_sel(struct ata_device *dev, unsigned int reg)
+static void piix_sidpr_sel(struct ata_link *link, unsigned int reg)
 {
-	struct ata_port *ap = dev->link->ap;
+	struct ata_port *ap = link->ap;
 	struct piix_host_priv *hpriv = ap->host->private_data;
 
-	iowrite32(((ap->port_no * 2 + dev->devno) << 8) | piix_sidx_map[reg],
+	iowrite32(((ap->port_no * 2 + link->pmp) << 8) | piix_sidx_map[reg],
 		  hpriv->sidpr + PIIX_SIDPR_IDX);
 }
 
-static int piix_sidpr_read(struct ata_device *dev, unsigned int reg)
-{
-	struct piix_host_priv *hpriv = dev->link->ap->host->private_data;
-
-	piix_sidpr_sel(dev, reg);
-	return ioread32(hpriv->sidpr + PIIX_SIDPR_DATA);
-}
-
-static void piix_sidpr_write(struct ata_device *dev, unsigned int reg, u32 val)
-{
-	struct piix_host_priv *hpriv = dev->link->ap->host->private_data;
-
-	piix_sidpr_sel(dev, reg);
-	iowrite32(val, hpriv->sidpr + PIIX_SIDPR_DATA);
-}
-
-static u32 piix_merge_scr(u32 val0, u32 val1, const int * const *merge_tbl)
-{
-	u32 val = 0;
-	int i, mi;
-
-	for (i = 0, mi = 0; i < 32 / 4; i++) {
-		u8 c0 = (val0 >> (i * 4)) & 0xf;
-		u8 c1 = (val1 >> (i * 4)) & 0xf;
-		u8 merged = c0;
-		const int *cur;
-
-		/* if no merge preference, assume the first value */
-		cur = merge_tbl[mi];
-		if (!cur)
-			goto done;
-		mi++;
-
-		/* if two values equal, use it */
-		if (c0 == c1)
-			goto done;
-
-		/* choose the first match or the last from the merge table */
-		while (*cur != -1) {
-			if (c0 == *cur || c1 == *cur)
-				break;
-			cur++;
-		}
-		if (*cur == -1)
-			cur--;
-		merged = *cur;
-	done:
-		val |= merged << (i * 4);
-	}
-
-	return val;
-}
-
 static int piix_sidpr_scr_read(struct ata_link *link,
 			       unsigned int reg, u32 *val)
 {
-	struct ata_port *ap = link->ap;
-	const int * const sstatus_merge_tbl[] = {
-		/* DET */ (const int []){ 1, 3, 0, 4, 3, -1 },
-		/* SPD */ (const int []){ 2, 1, 0, -1 },
-		/* IPM */ (const int []){ 6, 2, 1, 0, -1 },
-		NULL,
-	};
-	const int * const scontrol_merge_tbl[] = {
-		/* DET */ (const int []){ 1, 0, 4, 0, -1 },
-		/* SPD */ (const int []){ 0, 2, 1, 0, -1 },
-		/* IPM */ (const int []){ 0, 1, 2, 3, 0, -1 },
-		NULL,
-	};
-	u32 v0, v1;
+	struct piix_host_priv *hpriv = link->ap->host->private_data;
 
 	if (reg >= ARRAY_SIZE(piix_sidx_map))
 		return -EINVAL;
 
-	if (!(ap->flags & ATA_FLAG_SLAVE_POSS)) {
-		*val = piix_sidpr_read(&ap->link.device[0], reg);
-		return 0;
-	}
-
-	v0 = piix_sidpr_read(&ap->link.device[0], reg);
-	v1 = piix_sidpr_read(&ap->link.device[1], reg);
-
-	switch (reg) {
-	case SCR_STATUS:
-		*val = piix_merge_scr(v0, v1, sstatus_merge_tbl);
-		break;
-	case SCR_ERROR:
-		*val = v0 | v1;
-		break;
-	case SCR_CONTROL:
-		*val = piix_merge_scr(v0, v1, scontrol_merge_tbl);
-		break;
-	}
-
+	piix_sidpr_sel(link, reg);
+	*val = ioread32(hpriv->sidpr + PIIX_SIDPR_DATA);
 	return 0;
 }
 
 static int piix_sidpr_scr_write(struct ata_link *link,
 				unsigned int reg, u32 val)
 {
-	struct ata_port *ap = link->ap;
+	struct piix_host_priv *hpriv = link->ap->host->private_data;
 
 	if (reg >= ARRAY_SIZE(piix_sidx_map))
 		return -EINVAL;
 
-	piix_sidpr_write(&ap->link.device[0], reg, val);
-
-	if (ap->flags & ATA_FLAG_SLAVE_POSS)
-		piix_sidpr_write(&ap->link.device[1], reg, val);
-
+	piix_sidpr_sel(link, reg);
+	iowrite32(val, hpriv->sidpr + PIIX_SIDPR_DATA);
 	return 0;
 }
 
@@ -1370,28 +1269,28 @@ static const int *__devinit piix_init_sata_map(struct pci_dev *pdev,
 	return map;
 }
 
-static void __devinit piix_init_sidpr(struct ata_host *host)
+static int __devinit piix_init_sidpr(struct ata_host *host)
 {
 	struct pci_dev *pdev = to_pci_dev(host->dev);
 	struct piix_host_priv *hpriv = host->private_data;
-	struct ata_device *dev0 = &host->ports[0]->link.device[0];
+	struct ata_link *link0 = &host->ports[0]->link;
 	u32 scontrol;
-	int i;
+	int i, rc;
 
 	/* check for availability */
 	for (i = 0; i < 4; i++)
 		if (hpriv->map[i] == IDE)
-			return;
+			return 0;
 
 	if (!(host->ports[0]->flags & PIIX_FLAG_SIDPR))
-		return;
+		return 0;
 
 	if (pci_resource_start(pdev, PIIX_SIDPR_BAR) == 0 ||
 	    pci_resource_len(pdev, PIIX_SIDPR_BAR) != PIIX_SIDPR_LEN)
-		return;
+		return 0;
 
 	if (pcim_iomap_regions(pdev, 1 << PIIX_SIDPR_BAR, DRV_NAME))
-		return;
+		return 0;
 
 	hpriv->sidpr = pcim_iomap_table(pdev)[PIIX_SIDPR_BAR];
 
@@ -1399,7 +1298,7 @@ static void __devinit piix_init_sidpr(struct ata_host *host)
 	 * Give it a test drive by inhibiting power save modes which
 	 * we'll do anyway.
 	 */
-	scontrol = piix_sidpr_read(dev0, SCR_CONTROL);
+	piix_sidpr_scr_read(link0, SCR_CONTROL, &scontrol);
 
 	/* if IPM is already 3, SCR access is probably working.  Don't
 	 * un-inhibit power save modes as BIOS might have inhibited
@@ -1407,18 +1306,30 @@ static void __devinit piix_init_sidpr(struct ata_host *host)
 	 */
 	if ((scontrol & 0xf00) != 0x300) {
 		scontrol |= 0x300;
-		piix_sidpr_write(dev0, SCR_CONTROL, scontrol);
-		scontrol = piix_sidpr_read(dev0, SCR_CONTROL);
+		piix_sidpr_scr_write(link0, SCR_CONTROL, scontrol);
+		piix_sidpr_scr_read(link0, SCR_CONTROL, &scontrol);
 
 		if ((scontrol & 0xf00) != 0x300) {
 			dev_printk(KERN_INFO, host->dev, "SCR access via "
 				   "SIDPR is available but doesn't work\n");
-			return;
+			return 0;
 		}
 	}
 
-	host->ports[0]->ops = &piix_sidpr_sata_ops;
-	host->ports[1]->ops = &piix_sidpr_sata_ops;
+	/* okay, SCRs available, set ops and ask libata for slave_link */
+	for (i = 0; i < 2; i++) {
+		struct ata_port *ap = host->ports[i];
+
+		ap->ops = &piix_sidpr_sata_ops;
+
+		if (ap->flags & ATA_FLAG_SLAVE_POSS) {
+			rc = ata_slave_link_init(ap);
+			if (rc)
+				return rc;
+		}
+	}
+
+	return 0;
 }
 
 static void piix_iocfg_bit18_quirk(struct pci_dev *pdev)
@@ -1528,7 +1439,9 @@ static int __devinit piix_init_one(struct pci_dev *pdev,
 	/* initialize controller */
 	if (port_flags & ATA_FLAG_SATA) {
 		piix_init_pcs(host, piix_map_db_table[ent->driver_data]);
-		piix_init_sidpr(host);
+		rc = piix_init_sidpr(host);
+		if (rc)
+			return rc;
 	}
 
 	/* apply IOCFG bit18 quirk */