linux-kernel - Re: [PATCH] serial 8250: tighten test for using backup timer

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Message-ID: <87a5b0800808261110t7c36cf7bp6521b127db3408d4@mail.gmail.com>
Date:	Tue, 26 Aug 2008 19:10:34 +0100
From:	"Will Newton" <will.newton@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	"David Brownell" <david-b@...bell.net>,
	linux-kernel@...r.kernel.org, alex.williamson@...com
Subject: Re: [PATCH] serial 8250: tighten test for using backup timer

On 8/26/08, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Tue, 26 Aug 2008 10:45:34 -0700
>  David Brownell <david-b@...bell.net> wrote:
>
>  > > > Also, how serious is the problem which is being fixed here?  It
>  > > > _sounds_ like it's of the "fatal for people who have that hardware"
>  > > > variety, in which case we should get this into 2.6.27 and probably
>  > > > 2.6.26.x.  Not sure about 2.5.26.x though - the patch doesn't apply
>  > > > there, but I didn't check whether this is due to functional changes.
>  > >
>  > > For users of this version of this particular UART IP it is fatal. From
>  > > looking at the git history it looks like the original patch went into
>  > > 2.6.26 so it might also affect that kernel.
>  >
>  > Second that:  serial-8250-tighten-test-for-using-backup-timer.patch
>  > (from MMOTM) in mainline sooner-not-later seems right.
>
>
> ok, if you think so...
>
>  I still have an unanswered question out there about the init_timer()
>  handling in that area of the driver but afaict this patch didn't make any
>  of it worse than it already is.

Sorry, I forgot to follow up on that. I had a look at the init_timer()
usage and it looks correct although it is rather strange. Reworking it
would affect several classes of hardware, most of which I don't have
available so I think it's safest to leave it as is for now.

>  > My own exposure to this is that the UART on DaVinci hardware, which
>  > TI allegedly derived from its original 16550 logic, has periodically
>  > gone from working to unusable with the mainline 8250.c ... and back
>  > and forth a bunch.  Currently it's "unusable", a regression from some
>  > previous versions.  With this patch from Alex, it's usable.
>  >
>  > Of course there are a bunch of arch/arm/mach-davinci patches needed
>  > to make that platform more functional in mainline.  I expect they'll
>  > probably merge in the 2.6.28-rc0 window.  Meanwhile, running out of
>  > ramdisk with a serial console should at least work right!  :)
>  >
>
>
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