I/O issues with writing to mtdblock devices on kirkwood

[Mark Brown]

On Mon, Jan 11, 2016 at 03:00:59PM -0800, Martin Michlmayr wrote:
> A few months ago Debian users with QNAP devices (ARM Kirkwood)
> reported issues (mostly SATA timeouts) when doing kernel upgrades,
> specifically when the new ramdisk was being written to flash.

> cat file > /dev/mtdblockX worked fine on a 2 MB flash partition but
> resulted in SATA timeouts on a 9 MB flash partition.

> flascp file /dev/mtd2 works fine.

> I've now bisected it down to this change:

>  commit 0461a4149836c792d186027c8c859637a4cfb11a
>  Author: Mark Brown <broonie at kernel.org>
>  Date:   Tue Dec 9 21:38:05 2014 +0000

>      spi: Pump transfers inside calling context for spi_sync()

Can you please clarify?  You're saying this causes SATA timeouts but
this is a change in the SPI subsystem and you're talking about MTD
devices.  You've also not said which kernel version this is with...

In any case, please provide traces from ftrace with all the SPI trace
enabled (via /sys/kernel/debug/trace/events/spi/enable).
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