sata_mv delayed eh handling

Introduce a new "delayed error handling" mechanism in sata_mv,
to enable us to eventually deal with multiple simultaneous NCQ
failures on a single host link when a PM is present.

This involves a port flag (MV_PP_FLAG_DELAYED_EH) to prevent new
commands being queued, and a pmp bitmap to indicate which pmp links
had NCQ errors.

The new mv_pmp_error_handler() uses those values to invoke
ata_eh_analyze_ncq_error() on each failed link, prior to freezing
the port and passing control to sata_pmp_error_handler().

This is based upon a strategy suggested by Tejun.

For now, we just implement the delayed mechanism.
The next patch in this series will add the multiple-NCQ EH code
to take advantage of it.
Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_mv.c

@@ -367,6 +367,7 @@ enum {
 	MV_PP_FLAG_EDMA_EN	= (1 << 0),	/* is EDMA engine enabled? */
 	MV_PP_FLAG_NCQ_EN	= (1 << 1),	/* is EDMA set up for NCQ? */
 	MV_PP_FLAG_FBS_EN	= (1 << 2),	/* is EDMA set up for FBS? */
+	MV_PP_FLAG_DELAYED_EH	= (1 << 3),	/* delayed dev err handling */
 };
 
 #define IS_GEN_I(hpriv) ((hpriv)->hp_flags & MV_HP_GEN_I)
@@ -447,6 +448,7 @@ struct mv_port_priv {
 	unsigned int		resp_idx;
 
 	u32			pp_flags;
+	unsigned int		delayed_eh_pmp_map;
 };
 
 struct mv_port_signal {
@@ -542,6 +544,7 @@ static int mv_pmp_hardreset(struct ata_link *link, unsigned int *class,
 				unsigned long deadline);
 static int  mv_softreset(struct ata_link *link, unsigned int *class,
 				unsigned long deadline);
+static void mv_pmp_error_handler(struct ata_port *ap);
 
 /* .sg_tablesize is (MV_MAX_SG_CT / 2) in the structures below
  * because we have to allow room for worst case splitting of
@@ -589,7 +592,7 @@ static struct ata_port_operations mv6_ops = {
 	.pmp_hardreset		= mv_pmp_hardreset,
 	.pmp_softreset		= mv_softreset,
 	.softreset		= mv_softreset,
-	.error_handler		= sata_pmp_error_handler,
+	.error_handler		= mv_pmp_error_handler,
 };
 
 static struct ata_port_operations mv_iie_ops = {
@@ -1097,6 +1100,12 @@ static int mv_qc_defer(struct ata_queued_cmd *qc)
 	struct ata_port *ap = link->ap;
 	struct mv_port_priv *pp = ap->private_data;
 
+	/*
+	 * Don't allow new commands if we're in a delayed EH state
+	 * for NCQ and/or FIS-based switching.
+	 */
+	if (pp->pp_flags & MV_PP_FLAG_DELAYED_EH)
+		return ATA_DEFER_PORT;
 	/*
 	 * If the port is completely idle, then allow the new qc.
 	 */
@@ -1591,6 +1600,33 @@ static struct ata_queued_cmd *mv_get_active_qc(struct ata_port *ap)
 	return qc;
 }
 
+static void mv_pmp_error_handler(struct ata_port *ap)
+{
+	unsigned int pmp, pmp_map;
+	struct mv_port_priv *pp = ap->private_data;
+
+	if (pp->pp_flags & MV_PP_FLAG_DELAYED_EH) {
+		/*
+		 * Perform NCQ error analysis on failed PMPs
+		 * before we freeze the port entirely.
+		 *
+		 * The failed PMPs are marked earlier by mv_pmp_eh_prep().
+		 */
+		pmp_map = pp->delayed_eh_pmp_map;
+		pp->pp_flags &= ~MV_PP_FLAG_DELAYED_EH;
+		for (pmp = 0; pmp_map != 0; pmp++) {
+			unsigned int this_pmp = (1 << pmp);
+			if (pmp_map & this_pmp) {
+				struct ata_link *link = &ap->pmp_link[pmp];
+				pmp_map &= ~this_pmp;
+				ata_eh_analyze_ncq_error(link);
+			}
+		}
+		ata_port_freeze(ap);
+	}
+	sata_pmp_error_handler(ap);
+}
+
 static void mv_unexpected_intr(struct ata_port *ap, int edma_was_enabled)
 {
 	struct ata_eh_info *ehi = &ap->link.eh_info;