• Finn Thain's avatar
    ncr5380: Eliminate USLEEP_WAITLONG delay · 4d029e9a
    Finn Thain authored
    Linux 2.1.105 introduced the USLEEP_WAITLONG delay, apparently "needed for
    Mustek scanners". It is intended to stall the issue queue for 5 seconds.
    There are a number of problems with this.
    
    1. Only g_NCR5380 enables the delay, which implies that the other five
       drivers using the NCR5380.c core driver remain incompatible with
       Mustek scanners.
    
    2. The delay is not implemented by atari_NCR5380.c, which is problematic
       for re-unifying the two core driver forks.
    
    3. The delay is implemented using NCR5380_set_timer() which makes it
       unreliable. A new command queued by the mid-layer cancels the delay.
    
    4. The delay is applied indiscriminately in several situations in which
       NCR5380_select() returns -1. These are-- reselection by the target,
       failure of the target to assert BSY, and failure of the target to
       assert REQ. It's clear from the comments that USLEEP_WAITLONG is not
       relevant to the reselection case. And reportedly, these scanners do
       not disconnect.
    
    5. atari_NCR5380.c was forked before Linux 2.1.105, so it was spared some
       of the damage done to NCR5380.c. In this case, the atari_NCR5380.c core
       driver was more standard-compliant and may not have needed any
       workaround like the USLEEP_WAITLONG kludge. The compliance issue was
       addressed in the previous patch.
    
    If these scanners still don't work, we need a better solution. Retrying
    selection until EH aborts a command offers equivalent robustness. Bugs in
    the existing driver prevent EH working correctly but this is addressed in
    a subsequent patch. Remove USLEEP_WAITLONG.
    Signed-off-by: default avatarFinn Thain <fthain@telegraphics.com.au>
    Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
    Tested-by: default avatarOndrej Zary <linux@rainbow-software.org>
    Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
    4d029e9a
NCR5380.c 86.8 KB