Date: Mon, 24 Mar 2008 20:56:40 +0100 (CET) From: Stefan Richter Subject: 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 Signed-off-by: Jarod Wilson --- drivers/firewire/fw-card.c | 2 +- drivers/firewire/fw-topology.c | 2 +- drivers/firewire/fw-transaction.h | 9 +++++++++ 3 files changed, 11 insertions(+), 2 deletions(-) Index: linux/drivers/firewire/fw-card.c =================================================================== --- linux.orig/drivers/firewire/fw-card.c +++ linux/drivers/firewire/fw-card.c @@ -238,7 +238,7 @@ 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 Index: linux/drivers/firewire/fw-topology.c =================================================================== --- linux.orig/drivers/firewire/fw-topology.c +++ linux/drivers/firewire/fw-topology.c @@ -517,7 +517,7 @@ fw_core_handle_bus_reset(struct fw_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); Index: linux/drivers/firewire/fw-transaction.h =================================================================== --- linux.orig/drivers/firewire/fw-transaction.h +++ linux/drivers/firewire/fw-transaction.h @@ -257,6 +257,15 @@ struct fw_card { }; /* + * 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.