ncr5380: Eliminate selecting state
authorFinn Thain <fthain@telegraphics.com.au>
Sun, 3 Jan 2016 05:05:23 +0000 (16:05 +1100)
committerMartin K. Petersen <martin.petersen@oracle.com>
Thu, 7 Jan 2016 02:42:56 +0000 (21:42 -0500)
commitae753a3387504daa11b8779a00d37923f971c6d0
tree2249c062810abfb64f7b973af8de27d0c6e49646
parent2f854b82b001b5d05b4e1c81acb947f7bd9cee9f
ncr5380: Eliminate selecting state

Linux v2.1.105 changed the algorithm for polling for the BSY signal
in NCR5380_select() and NCR5380_main().

Presently, this code has a bug. Back then, NCR5380_set_timer(hostdata, 1)
meant reschedule main() after sleeping for 10 ms. Repeated 25 times this
provided the recommended 250 ms selection time-out delay. This got broken
when HZ became configurable.

We could fix this but there's no need to reschedule the main loop. This
BSY polling presently happens when the NCR5380_main() work queue item
calls NCR5380_select(), which in turn schedules NCR5380_main(), which
calls NCR5380_select() again, and so on.

This algorithm is a deviation from the simpler one in atari_NCR5380.c.
The extra complexity and state is pointless. There's no reason to
stop selection half-way and return to to the main loop when the main
loop can do nothing useful until selection completes.

So just poll for BSY. We can sleep while polling now that we have a
suitable workqueue.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Ondrej Zary <linux@rainbow-software.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
drivers/scsi/NCR5380.c
drivers/scsi/NCR5380.h
drivers/scsi/atari_NCR5380.c