libata-pmp-prep: implement ATA_LFLAG_NO_RETRY

Some PMP links are connected to internal pseudo devices which may come
and go depending on situation.  There's no reason to try hard to
recover them.  ATA_LFLAG_NO_RETRY tells EH to not retry if the device
attached to the link fails.
Signed-off-by: NTejun Heo <htejun@gmail.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/ata/libata-eh.c

@@ -2335,7 +2335,10 @@ int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 		struct ata_eh_context *ehc = &link->eh_context;
 
 		ata_link_for_each_dev(dev, link) {
-			ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;
+			if (link->flags & ATA_LFLAG_NO_RETRY)
+				ehc->tries[dev->devno] = 1;
+			else
+				ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;
 
 			/* collect port action mask recorded in dev actions */
 			ehc->i.action |= ehc->i.dev_action[dev->devno] &

include/linux/libata.h

@@ -169,6 +169,7 @@ enum {
 	ATA_LFLAG_ASSUME_ATA	= (1 << 3), /* assume ATA class */
 	ATA_LFLAG_ASSUME_SEMB	= (1 << 4), /* assume SEMB class */
 	ATA_LFLAG_ASSUME_CLASS	= ATA_LFLAG_ASSUME_ATA | ATA_LFLAG_ASSUME_SEMB,
+	ATA_LFLAG_NO_RETRY	= (1 << 5), /* don't retry this link */
 
 	/* struct ata_port flags */
 	ATA_FLAG_SLAVE_POSS	= (1 << 0), /* host supports slave dev */