Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers

From	Ondrej Zary <linux@rainbow-software.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers
Date	2015-11-24 22:50 +0100
Message-ID	<qytDj-5dS-3@gated-at.bofh.it> (permalink)
References	<qw6Bc-vx-5@gated-at.bofh.it> <qygPM-5uK-9@gated-at.bofh.it> <qyhVv-6c8-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tuesday 24 November 2015 10:13:17 Finn Thain wrote:
> 
> On Tue, 24 Nov 2015, Ondrej Zary wrote:
> 
> > On Tuesday 24 November 2015, Finn Thain wrote:
> > > 
> > > On Mon, 23 Nov 2015, Ondrej Zary wrote:
> > > 
> > > > 
> > > > 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.
> > > > 
> > > 
> > > A 128-byte PDMA receive followed by 126-byte PDMA receive? I don't see 
> > > how that is possible given round_down(126, 128) == 0. Was this the 
> > > actual 'len' argument to NCR5380_pread() in g_NCR5380.c?
> > 
> > No 126-byte PDMA. The 126 bytes were probably lost (or mixed with the 
> > next read?).
> 
> When you said, the "PDMA operation hangs waiting forever", I figured that 
> you had hit an infinite loop in NCR5380_pread()... but now I'm lost.
> 
> My main concern here is to confirm that I didn't break anything e.g. with 
> patch 24 or 41. It would be nice to know that this hang is not the result 
> of a new bug.
> 
> > The next read was also 254 bytes so another 128-byte PDMA transfer.
> > 
> > Then modified NCR5380_information_transfer() to transfer the remaining 
> > data (126 bytes in this case) using PIO. It did not help, the next PDMA 
> > transfer failed too.
> > 
> 
> AFAICT, no change to NCR5380_information_transfer() should be needed. It 
> was always meant to cope with the need to split a transfer between (P)DMA 
> and PIO.

Instead of fixing split transfers, simply forced everything non-modulo-128 to
PIO:
--- a/drivers/scsi/g_NCR5380.c
+++ b/drivers/scsi/g_NCR5380.c
@@ -703,6 +703,10 @@ static int generic_NCR5380_dma_xfer_len(struct scsi_cmnd *cmd)
 	    !(cmd->SCp.this_residual % transfersize))
 		transfersize = 32 * 1024;

+	/* 53C400 datasheet: non-modulo-128-byte transfers should use PIO */
+	if (transfersize % 128)
+		transfersize = 0;
+
 	return transfersize;
 }

It seems to work and greatly improves performance:
# hdparm -t --direct /dev/sdb

/dev/sdb:
 Timing O_DIRECT disk reads:   4 MB in  4.84 seconds = 846.15 kB/sec

-- 
Ondrej Zary
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Thread

[PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-18 10:20 +0100
  [PATCH 04/71] ncr5380: Remove more pointless macros Finn Thain <fthain@telegraphics.com.au> - 2015-11-18 10:30 +0100
  Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-18 12:40 +0100
    Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-19 03:30 +0100
      Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Michael Schmitz <schmitzmic@gmail.com> - 2015-11-19 04:00 +0100
      Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-19 08:50 +0100
      Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-20 00:00 +0100
        Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-20 02:50 +0100
          Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-20 08:30 +0100
            Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Christoph Hellwig <hch@infradead.org> - 2015-11-20 08:40 +0100
              Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-20 09:20 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-20 10:20 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Christoph Hellwig <hch@infradead.org> - 2015-11-20 11:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-20 12:00 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Christoph Hellwig <hch@infradead.org> - 2015-11-20 12:50 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-20 12:50 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Geert Uytterhoeven <geert@linux-m68k.org> - 2015-11-20 13:30 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-20 13:50 +0100
          Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-20 08:40 +0100
          Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-20 19:30 +0100
            Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-21 03:10 +0100
              Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-21 14:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-22 00:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-22 00:40 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-24 00:00 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-24 02:30 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-24 09:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-24 10:20 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-24 13:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-24 19:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-24 22:50 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-25 03:20 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-25 10:10 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380  drivers Finn Thain <fthain@telegraphics.com.au> - 2015-11-25 13:00 +0100
                Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers Ondrej Zary <linux@rainbow-software.org> - 2015-11-26 00:10 +0100
  [PATCH 72/71] ncr5380: Fix pseudo-DMA Ondrej Zary <linux@rainbow-software.org> - 2015-11-25 22:40 +0100
  [RFC PATCH 73/71] ncr5380: Use runtime register mapping Ondrej Zary <linux@rainbow-software.org> - 2015-11-29 10:50 +0100
    Re: [RFC PATCH 73/71] ncr5380: Use runtime register mapping Finn Thain <fthain@telegraphics.com.au> - 2015-11-30 13:00 +0100
  [RFC PATCH 74/71] ncr5380: Enable PDMA for NCR53C400A Ondrej Zary <linux@rainbow-software.org> - 2015-11-29 10:50 +0100
    Re: [RFC PATCH 74/71] ncr5380: Enable PDMA for NCR53C400A Finn Thain <fthain@telegraphics.com.au> - 2015-11-30 13:00 +0100
    Re: [RFC PATCH 74/71] ncr5380: Enable PDMA for NCR53C400A Finn Thain <fthain@telegraphics.com.au> - 2015-11-30 13:10 +0100
      Re: [RFC PATCH 74/71] ncr5380: Enable PDMA for NCR53C400A Ondrej Zary <linux@rainbow-software.org> - 2015-11-30 14:50 +0100
  [RFC PATCH 75/71] ncr5380: Remove FLAG_DTC3181E Ondrej Zary <linux@rainbow-software.org> - 2015-11-29 11:10 +0100
    Re: [RFC PATCH 75/71] ncr5380: Remove FLAG_DTC3181E Finn Thain <fthain@telegraphics.com.au> - 2015-11-30 06:00 +0100

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