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Subject[PATCH] 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>
---
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
@@ -240,7 +240,7 @@ 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
@@ -518,7 +518,7 @@ 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
@@ -261,6 +261,15 @@ 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.
--
Stefan Richter
-=====-==--- --== ==---
http://arcgraph.de/sr/


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