[PATCH] scsi: mvme16x: enable 53c710 burst-8 hardware transfer mode

[PATCH] scsi: mvme16x: enable 53c710 burst-8 hardware transfer mode

[Denis Ahrens]

The shared 53c700.c backend runs the 53c710 with burst mode disabled
when hostdata->burst_length is left unset: NCR_700_chip_setup() falls
through to BURST_DISABLE in CTEST7 and a 1-byte burst length in
DMODE_710_REG, so the chip delivers one byte per transfer period.
The other 53c710 hosts in-tree already use it: sim710 and lasi700 pick
burst 8, sni_53c710 burst 4.

A/B verified on an MVME177 (53c710 rev 2, ZuluSCSI drives):
  raw reads 16 MiB @64k  4.7/4.8/5.1 -> 5.8/6.1/6.7 MB/s (+23..26%)
  4 MiB @16k             3.4 -> 4.4 MB/s
  4 MiB @4k              3.2 -> 3.9 MB/s
  4 MiB @512B            2.1 -> 2.2 MB/s (small-buffer case is SCSI
                         command-count bound; burst only raises bytes
                         per command, not commands)
  writes                 unchanged (filesystem-bound, not ASIC-bound)

Integrity: a 16 MiB /dev/urandom payload round-trips bit-exact on a
cold read (sync + drop_caches, md5 verified write vs read); dmesg
clean with no timeouts, sense errors, retries or resets.

Signed-off-by: Denis Ahrens <denis@h3q.com>
---
 drivers/scsi/mvme16x_scsi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/mvme16x_scsi.c b/drivers/scsi/mvme16x_scsi.c
index f4db93c13986..ff6b22c864a9 100644
--- a/drivers/scsi/mvme16x_scsi.c
+++ b/drivers/scsi/mvme16x_scsi.c
@@ -60,6 +60,7 @@ static int mvme16x_probe(struct platform_device *dev)
 	hostdata->base = (void __iomem *)0xfff47000UL;
 	hostdata->clock = 50;	/* XXX - depends on the CPU clock! */
 	hostdata->chip710 = 1;
+	hostdata->burst_length = 8;
 	hostdata->dmode_extra = DMODE_FC2;
 	hostdata->dcntl_extra = EA_710;
 	hostdata->ctest7_extra = CTEST7_TT1;

base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
-- 
2.43.0

Re: [PATCH] scsi: mvme16x: enable 53c710 burst-8 hardware transfer mode

[Martin K. Petersen]

Denis,

> The shared 53c700.c backend runs the 53c710 with burst mode disabled
> when hostdata->burst_length is left unset: NCR_700_chip_setup() falls
> through to BURST_DISABLE in CTEST7 and a 1-byte burst length in
> DMODE_710_REG, so the chip delivers one byte per transfer period. The
> other 53c710 hosts in-tree already use it: sim710 and lasi700 pick
> burst 8, sni_53c710 burst 4.

Applied to 7.5/scsi-staging, thanks!

-- 
Martin K. Petersen