firewire: unnecessary BM delay after generation rollover

Noticed by Jarod Wilson:  The bus manager work was unnecessarily delayed
each time the bus generation counter rolled over.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Jarod Wilson <jwilson@redhat.com>

3 files changed, 11 insertions, 2 deletions

diff --git a/drivers/firewire/fw-card.c b/drivers/firewire/fw-card.c
index 6bd91a15d5e6..17a80cecdc14 100644
--- a/drivers/firewire/fw-card.c
+++ b/drivers/firewire/fw-card.c
@@ -232,7 +232,7 @@ fw_card_bm_work(struct work_struct *work)
         root_id = root_node->node_id;
         grace = time_after(jiffies, card->reset_jiffies + DIV_ROUND_UP(HZ, 10));
 
-        if (card->bm_generation + 1 == generation ||
+        if (is_next_generation(generation, card->bm_generation) ||
             (card->bm_generation != generation && grace)) {
                 /*
                  * This first step is to figure out who is IRM and
diff --git a/drivers/firewire/fw-topology.c b/drivers/firewire/fw-topology.c
index e7520e4bd6bc..8dd6703b55cd 100644
--- a/drivers/firewire/fw-topology.c
+++ b/drivers/firewire/fw-topology.c
@@ -523,7 +523,7 @@ fw_core_handle_bus_reset(struct fw_card *card,
          * previously processed one, we cannot reliably compare the
          * old and new topologies.
          */
-        if ((generation & 0xff) != ((card->generation + 1) & 0xff) &&
+        if (!is_next_generation(generation, card->generation) &&
             card->local_node != NULL) {
                 fw_notify("skipped bus generations, destroying all nodes\n");
                 fw_destroy_nodes(card);
diff --git a/drivers/firewire/fw-transaction.h b/drivers/firewire/fw-transaction.h
index c9ab12a15f6e..1d78e9cc5940 100644
--- a/drivers/firewire/fw-transaction.h
+++ b/drivers/firewire/fw-transaction.h
@@ -276,6 +276,15 @@ static inline void fw_card_put(struct fw_card *card)
 extern void fw_schedule_bm_work(struct fw_card *card, unsigned long delay);
 
 /*
+ * Check whether new_generation is the immediate successor of old_generation.
+ * Take counter roll-over at 255 (as per to OHCI) into account.
+ */
+static inline bool is_next_generation(int new_generation, int old_generation)
+{
+        return (new_generation & 0xff) == ((old_generation + 1) & 0xff);
+}
+
+/*
  * The iso packet format allows for an immediate header/payload part
  * stored in 'header' immediately after the packet info plus an
  * indirect payload part that is pointer to by the 'payload' field.