linux-kernel - Re: [2.6.23-rc3 possible regression] 8250 claims nonexisting device blocking IO port

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Message-Id: <200708202028.22806.arvidjaar@mail.ru>
Date:	Mon, 20 Aug 2007 20:28:22 +0400
From:	Andrey Borzenkov <arvidjaar@...l.ru>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	linux-serial@...r.kernel.org,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6.23-rc3 possible regression] 8250 claims nonexisting device blocking IO port

On Monday 20 August 2007, Bjorn Helgaas wrote:
> On Saturday 18 August 2007 01:07:55 am Andrey Borzenkov wrote:
> > This is related to thread "2.6.22-rc: regression: no irda0 interface
> > (2.6.21 was OK), smsc does not find chip" but it is already way too
> > overloaded.
> >
> > In 2.6.23 smsc-ircc2 fails to initialize IrDA controller. Apparently
> > because it by default is using the same IO port as ttyS3 and this is now
> > claimed by 8250.
>
> 8250 should have claimed ttyS3 in 2.6.21 and earlier.  So from
> the 8250 point of view, 2.6.21 and 2.6.23 should behave the same.
>

I only know that this worked in 2.6.21. I remind that previous regression was 
post-2.6.21 which obviously implies that it did work ...

For reference I attach dmesg from 2.6.21. I do not see any ttyS3 there ...

> From the smsc-ircc2 point of view, 2.6.21 and 2.6.23 should work
> the same except for the additional quirk_smc_enable().  If
> 2.6.23 is worse than 2.6.21, please try removing the body of
> quirk_smc_enable() and see whether that makes 2.6.23 as good
> as 2.6.21.
>

This worked in 2.6.22 with the same quirks. I will test without later but I 
fail to see how they are related.

> For smsc-ircc2, 2.6.23 is definitely a regression from 2.6.22,
> because 8250 stayed out of the way in 2.6.22.  But we had to
> revert 8250 back to the 2.6.21 behavior because the change
> swapped ttyS0 and ttyS1 on some machines, so we just have to
> live with that 8250/smsc-ircc2 conflict for the time being.
>

This worked in 2.6.21 and 2.6.22 (and earlier BTW). So if you just had revert 
to 2.6.21 it would have worked. Something else changed.

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