On Sunday 22 November 2015 00:32:31 Finn Thain wrote:
On Sat, 21 Nov 2015, Ondrej Zary wrote:
On Saturday 21 November 2015 02:58:57 Finn Thain wrote:
I gather that your setup here is a QUANTUM LP240S target with Domex
3181 (DTC-436) card and g_NCR5380 module. I've been testing a similar
setup: QUANTUM LPS540S target with a Domex 3191D (DTC-536) card and
dmx3191d module. In both setups PIO is used exclusively, no IRQ is
used, and FLAG_DTC3181E is set. I didn't see any issues in my tests,
so your results are surprising.
I agree that the results are surprising. Even tried 2.4 kernels (Debian
3.1) and even 2.2 (Debian 3.0) and nothing worked. HW is fine - the
drive is accessible in Windows 98 (with Domex driver installed).
That's good to know (and very thorough).
Now testing the Canon FG2-5202 controller - a simple 8-bit ISA card with
only two chips: NCR 53C400 and 74LS245. It's memory mapped, IRQ
hardwired to 7.
# modprobe g_NCR5380_mmio ncr_irq=255 ncr_addr=0xd8000 ncr_53c400=1
[ 1245.919223] scsi2 : interrupts not enabled. for better interactive performance,
[ 1245.919326] scsi2 : please jumper the board for a free IRQ.
[ 1245.919389] scsi host2: Generic NCR5380/NCR53C400 SCSI, io_port 0x0, n_io_port 0, base 0xd8000, irq 0, can_queue 16, cmd_per_lun 2, sg_tablesize 128, this_id 7, flags { NCR53C400 }, USLEEP_POLL 3, USLEEP_WAITLONG 1250, options { AUTOPROBE_IRQ PSEUDO_DMA NCR53C400 }
[ 1246.376738] scsi 2:0:1:0: Direct-Access QUANTUM LP240S GM240S01X 4.6 PQ: 0 ANSI: 2 CCS
[ 1248.202198] sd 2:0:1:0: Attached scsi generic sg1 type 0
[ 1248.420856] 53C400r: no 53C80 gated irq after transfer
[ 1248.420948] 53C400r: no end dma signal
[ 1248.422459] sd 2:0:1:0: [sdb] Sector size 0 reported, assuming 512.
Seems that the PSEUDO_DMA is broken.
That's been my experience with mac_scsi also (going back 10 years). I'm
told that it used to work in v2.2. PIO was always usable though hopelessly
slow.
I haven't yet done any work on the PDMA problem with mac_scsi because
crashing bugs and the forked core driver seemed to be the more pressing
problems. And resolving the fork has implications for all of the DMA
variations anyway.
PDMA seems to be broken in multiple ways. NCR5380_pread cannot process less
than 128 bytes. In fact, 53C400 datasheet says that it's HW limitation:
non-modulo-128-byte transfers should use PIO.
Adding
transfersize = round_down(transfersize, 128);
to generic_NCR5380_dma_xfer_len() improves the situation a bit.
After modprobe, some small reads (8, 4, 24 and 64 bytes) are done using PIO,
then eight 512-byte reads using PDMA and then it fails on a 254-byte read.
First 128 bytes are read using PDMA and the next PDMA operation hangs waiting
forever for the host buffer to be ready.
--
Ondrej Zary
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