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-rw-r--r--drivers/firewire/core-card.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c
index 8aaa7fcb2..401a77e3b 100644
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -500,7 +500,19 @@ static void bm_work(struct work_struct *work)
fw_notice(card, "phy config: new root=%x, gap_count=%d\n",
new_root_id, gap_count);
fw_send_phy_config(card, new_root_id, generation, gap_count);
- reset_bus(card, true);
+ /*
+ * Where possible, use a short bus reset to minimize
+ * disruption to isochronous transfers. But in the event
+ * of a gap count inconsistency, use a long bus reset.
+ *
+ * As noted in 1394a 8.4.6.2, nodes on a mixed 1394/1394a bus
+ * may set different gap counts after a bus reset. On a mixed
+ * 1394/1394a bus, a short bus reset can get doubled. Some
+ * nodes may treat the double reset as one bus reset and others
+ * may treat it as two, causing a gap count inconsistency
+ * again. Using a long bus reset prevents this.
+ */
+ reset_bus(card, card->gap_count != 0);
/* Will allocate broadcast channel after the reset. */
goto out;
}