linux-kernel - Re: [PATCH v3 06/12] spi: spi-fsl-dspi: Replace interruptible wait queue with a simple completion

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Message-ID: <d05fda0e119405343e540b9768db534f@walle.cc>
Date:   Mon, 16 Mar 2020 14:25:02 +0100
From:   Michael Walle <michael@...le.cc>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, Esben Haabendal <eha@...f.com>,
        angelo@...am.it, andrew.smirnov@...il.com,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Wei Chen <weic@...dia.com>, Mohamed Hosny <mhosny@...dia.com>,
        peng.ma@....com
Subject: Re: [PATCH v3 06/12] spi: spi-fsl-dspi: Replace interruptible wait
 queue with a simple completion

Am 2020-03-16 14:00, schrieb Vladimir Oltean:
> On Mon, 16 Mar 2020 at 14:49, Mark Brown <broonie@...nel.org> wrote:
>> 
>> On Mon, Mar 16, 2020 at 02:29:09PM +0200, Vladimir Oltean wrote:
>> 
>> > Correct, the real problem is that I forgot to add a Fixes: tag for
>> > patch 5. I'll do that now.
>> 
>> OK.  The series otherwise looked fine but I'll wait for testing.
>> Michael, if there's issues remaining it might be good to get some
>> Tested-bys for the patches prior to whatever's broken so we can get
>> those fixes in (but obviously verifying that is work so only if you
>> have time).

I'm just about to test it. While my former "cat /dev/mtdN > /dev/null"
is working. I had the impression that it was slower, so I tried to test
it with dd now and a known chunk size.. only to find out that it is
still not working:

# dmesg|grep spi
[    1.894891] spi-nor spi1.0: w25q128fw (16384 Kbytes)
..
# time cat /dev/mtd0 > /dev/null
real    0m 30.73s
user    0m 0.00s
sys     0m 1.02s
# dd if=/dev/mtd0 of=/dev/null bs=64
262144+0 records in
262144+0 records out
# dd if=/dev/mtd0 of=/dev/null bs=64
262144+0 records in
262144+0 records out
# dd if=/dev/mtd0 of=/dev/null bs=64
dd: /dev/mtd0: Input/output error

I also wanted to test how it behaves if there are multiple processes
access the /dev/mtdN device. I haven't found the time to dig into
the call chain if see if there is any locking. Because what happens
if transfer_one_message() is called twice at the same time from two
different processes?

> 
> This time I verified with a protocol analyzer all transfer lengths
> from 1 all the way to 256, with this script:
> 
> #!/bin/bash
> 
> buf=''
> 
> for i in $(seq 0 255); do
> »       buf="${buf}\x$(printf '%02x' ${i})"
> »       spidev_test --device /dev/spidev2.0 --bpw 8 --cpha --speed
> 5000000 -p "${buf}"
> done
> 
> It looked fine as far as I could tell, and also the problems
> surrounding Ctrl-C are no longer present. Nonetheless it would be good
> if Michael could confirm, but I know that he's very busy too so it's
> understandable if he can no longer spend time on this.

I'm working on it ;)

-michael