linux-kernel - Re: Revert "serial: 8250: Make SERIAL_8250_RUNTIME

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Date:	Mon, 3 Jun 2013 13:03:22 -0400
From:	Kyle McMartin <kyle@...radead.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Kyle McMartin <kyle@...radead.org>, linux-kernel@...r.kernel.org,
	karthik.manamcheri@...il.com, torvalds@...uxfoundation.org
Subject: Re: Revert "serial: 8250: Make SERIAL_8250_RUNTIME_UARTS work
 correctly"

On Mon, Jun 03, 2013 at 09:55:31AM -0700, Greg KH wrote:
> On Mon, Jun 03, 2013 at 09:38:26AM -0400, Kyle McMartin wrote:
> > This reverts commit cfcec52e9781f08948c6eb98198d65c45be75a70.
> > 
> > This regresses a longstanding behaviour on X86 systems, which end up with
> > PCI serial ports moving between ttyS4 and ttyS0 when you bisect to opposite
> > sides of this commit, resulting in the need to constantly modify the console
> > setting in order to bisect across it.
> > 
> > Please revert, we can work on solving this for ARM platforms in a less
> > disruptive way.
> 
> Ugh, how did this break x86 systems?  Karthik, you said this wouldn't
> affect anyone else, what did you test it on?
>
> > Signed-off-by: Kyle McMartin <kyle@...artin.ca>
> 
> I'll go queue this up for the next -rc release, thanks Kyle.
> 

No worries, I undertand what Karthik is talking about, so I'll try to
figure this out.

CONFIG_SERIAL_8250_NR_UARTS=32
CONFIG_SERIAL_8250_RUNTIME_UARTS=4

is what was set in my .config, resulting in:

[3.9.y]
0: uart:16550A port:00001030 irq:16 tx:16522 rx:0 RTS|CTS|DTR|CD
1: uart:unknown port:000002F8 irq:3
2: uart:unknown port:000003E8 irq:4
3: uart:unknown port:000002E8 irq:3

[3.10-rc2]
0: uart:unknown port:000003F8 irq:4
1: uart:unknown port:000002F8 irq:3
2: uart:unknown port:000003E8 irq:4
3: uart:unknown port:000002E8 irq:3
4: uart:16550A port:00001030 irq:16 tx:16226 rx:0 RTS|CTS|DTR|CD

There's undeniably something wrong if RUNTIME_UARTS=0 doesn't result
in his serial ports showing up, I'll try to help debug that, but I
think the 3.9 behaviour is desireable if no "legacy" uarts are found.

regards, Kyle
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