linux-kernel - Re: [PATCH 1/2] I/OAT: Add watchdog/reset functionality to ioatdma driver

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Date:	Fri, 11 Jul 2008 13:07:24 -0700
From:	"Dan Williams" <dan.j.williams@...el.com>
To:	"Maciej Sosnowski" <maciej.sosnowski@...el.com>
Cc:	shannon.nelson@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] I/OAT: Add watchdog/reset functionality to ioatdma driver

On Fri, Jul 11, 2008 at 4:36 AM, Maciej Sosnowski
<maciej.sosnowski@...el.com> wrote:
> Due to occasional DMA channel hangs observed for I/OAT versions 1.2 and 2.0
> a watchdog has been introduced to check every 2 seconds
> if all channels progress normally.
> If stuck channel is detected, driver resets it.
> The reset is done in two parts. The second part is scheduled
> by the first one to reinitialize the channel after the restart.
>

checkpatch had some valid suggestions, please give it a run.

A general comment about this change it seems to add a bit of
complexity.  The driver now has two workqueue routines and a tasklet.
Might some of these be combined?  In other words, do we need a free
running watchdog when no descriptors are in flight?  It seems that
using a timer to kick the cleanup tasklet could be used in place of
the ioat_dma_chan_watchdog workqueue.

> Sleep time in self_test has been increased to 10ms
> since in some cases 1ms appeared not to be enough.

This should be broken out into a separate patch.  Perhaps with an
explanation of why it needs extra time for this particular
transaction.

Regards,
Dan
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