[PATCH v3 18/77] ncr5380: Eliminate USLEEP_WAITLONG delay

Finn Thain
2015-12-22T01:17:56Z

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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: Finn Thain <fthain@telegraphics.com.au>

---
drivers/scsi/NCR5380.c | 19 +++++--------------
drivers/scsi/g_NCR5380.c | 1 -
2 files changed, 5 insertions(+), 15 deletions(-)

Index: linux/drivers/scsi/NCR5380.c
===================================================================
--- linux.orig/drivers/scsi/NCR5380.c 2015-12-22 12:15:51.000000000 +1100
+++ linux/drivers/scsi/NCR5380.c 2015-12-22 12:15:52.000000000 +1100
@@ -468,10 +468,6 @@ static void NCR5380_print_phase(struct S
#ifndef USLEEP_POLL
#define USLEEP_POLL msecs_to_jiffies(200)
#endif
-#ifndef USLEEP_WAITLONG
-/* RvC: (reasonable time to wait on select error) */
-#define USLEEP_WAITLONG USLEEP_SLEEP
-#endif

/*
* Function : int should_disconnect (unsigned char cmd)
@@ -619,8 +615,8 @@ static void prepare_info(struct Scsi_Hos
"can_queue %d, cmd_per_lun %d, "
"sg_tablesize %d, this_id %d, "
"flags { %s%s%s%s}, "
-#if defined(USLEEP_POLL) && defined(USLEEP_WAITLONG)
- "USLEEP_POLL %lu, USLEEP_WAITLONG %lu, "
+#if defined(USLEEP_POLL) && defined(USLEEP_SLEEP)
+ "USLEEP_POLL %lu, USLEEP_SLEEP %lu, "
#endif
"options { %s} ",
instance->hostt->name, instance->io_port, instance->n_io_port,
@@ -631,8 +627,8 @@ static void prepare_info(struct Scsi_Hos
hostdata->flags & FLAG_DTC3181E ? "DTC3181E " : "",
hostdata->flags & FLAG_NO_PSEUDO_DMA ? "NO_PSEUDO_DMA " : "",
hostdata->flags & FLAG_TOSHIBA_DELAY ? "TOSHIBA_DELAY " : "",
-#if defined(USLEEP_POLL) && defined(USLEEP_WAITLONG)
- USLEEP_POLL, USLEEP_WAITLONG,
+#if defined(USLEEP_POLL) && defined(USLEEP_SLEEP)
+ USLEEP_POLL, USLEEP_SLEEP,
#endif
#ifdef AUTOPROBE_IRQ
"AUTOPROBE_IRQ "
@@ -1030,15 +1026,10 @@ static void NCR5380_main(struct work_str
if (!NCR5380_select(instance, tmp)) {
/* OK or bad target */
} else {
- /* RvC: device failed, so we wait a long time
- this is needed for Mustek scanners, that
- do not respond to commands immediately
- after a scan */
- printk(KERN_DEBUG "scsi%d: device %d did not respond in time\n", instance->host_no, tmp->device->id);
LIST(tmp, hostdata->issue_queue);
tmp->host_scribble = (unsigned char *) hostdata->issue_queue;
hostdata->issue_queue = tmp;
- NCR5380_set_timer(hostdata, USLEEP_WAITLONG);
+ done = 0;
}
} /* if hostdata->selecting */
if (hostdata->connected
Index: linux/drivers/scsi/g_NCR5380.c
===================================================================
--- linux.orig/drivers/scsi/g_NCR5380.c 2015-12-22 12:15:38.000000000 +1100
+++ linux/drivers/scsi/g_NCR5380.c 2015-12-22 12:15:52.000000000 +1100
@@ -59,7 +59,6 @@
/* settings for DTC3181E card with only Mustek scanner attached */
#define USLEEP_POLL msecs_to_jiffies(10)
#define USLEEP_SLEEP msecs_to_jiffies(200)
-#define USLEEP_WAITLONG msecs_to_jiffies(5000)

#define AUTOPROBE_IRQ