firewire: core: integrate software-forced bus resets with bus management

Bus resets which are triggered
  - by the kernel drivers after updates of the local nodes' config ROM,
  - by userspace software via ioctl
shall be deferred until after >=2 seconds after the last bus reset.

If multiple modifications of the local nodes' config ROM happen in a row,
only a single bus reset should happen after them.

When the local node's link goes from inactive to active or vice versa,
and at the two occasions of bus resets mentioned above --- and if the
current gap count differs from 63 --- the bus reset should be preceded
by a PHY configuration packet that reaffirms the gap count.  Otherwise a
bus manager would have to reset the bus again right after that.

This is necessary to promote bus stability, e.g. leave grace periods for
allocations and reallocations of isochronous channels and bandwidth,
SBP-2 reconnections etc.; see IEEE 1394 clause 8.2.1.

This change implements all of the above by moving bus reset initiation
into a delayed work (except for bus resets which are triggered by the
bus manager workqueue job and are performed there immediately).  It
comes with a necessary addition to the card driver methods that allows
to get the current gap count from PHY registers.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index db30a752a87a..adc5b55e6e5f 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -114,8 +114,10 @@ struct fw_card {
 
 	struct list_head link;
 
-	/* Work struct for BM duties. */
-	struct delayed_work work;
+	struct delayed_work br_work; /* bus reset job */
+	bool br_short;
+
+	struct delayed_work bm_work; /* bus manager job */
 	int bm_retries;
 	int bm_generation;
 	__be32 bm_transaction_data[2];