+/*
+ * 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.
+ */
+static const int piix_sidx_map[] = {
+ [SCR_STATUS] = 0,
+ [SCR_ERROR] = 2,
+ [SCR_CONTROL] = 1,
+};
+
+static void piix_sidpr_sel(struct ata_device *dev, unsigned int reg)
+{
+ struct ata_port *ap = dev->link->ap;
+ struct piix_host_priv *hpriv = ap->host->private_data;
+
+ iowrite32(((ap->port_no * 2 + dev->devno) << 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_port *ap, unsigned int reg, u32 *val)
+{
+ 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;
+
+ 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;
+ }
+
+ return 0;
+}
+
+static int piix_sidpr_scr_write(struct ata_port *ap, unsigned int reg, u32 val)
+{
+ 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);
+
+ return 0;
+}
+