linux-kernel - Re: [PATCH] serial: fix Kconfig for Freescale 16550

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Date:	Tue, 13 Dec 2011 13:58:56 +1100
From:	Michael Neuling <mikey@...ling.org>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
cc:	Greg KH <gregkh@...e.de>, Alan Cox <alan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, sfr@...b.auug.org.au,
	linux-next@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Michal Marek <mmarek@...e.cz>
Subject: Re: [PATCH] serial: fix Kconfig for Freescale 16550

In message <20111213024738.GA17663@...driver.com> you wrote:
> [Re: [PATCH] serial: fix Kconfig for Freescale 16550] On 13/12/2011 (Tue 12:5
3) Michael Neuling wrote:
> 
> > In message <20111213005444.GA27190@...e.de> you wrote:
> 
> [...]
> 
> > > Then you can't select SERIAL_8250 as a module at all, right?  
> > 
> > Correct, unless SERIAL_8250_FOL=n of course.
> > 
> > > Perhaps you should allow SERIAL_8250_FSL to be a module as well here?
> > > So changing the bool to a tristate should be the correct option?  Can
> > > you try that?
> > 
> > Yep, that works also.  New patch below.  
> > 
> > This should probably be aced by Paul to ensure he's cool with it being
> > a module now. 
> 
> This will still be broken, but in a different place and for different
> boards.  [The legacy_serial.c won't link for 8250=m on FSL boards.]
> 
> I think your original fix was closer to the right one.   Let me expand
> on that.   This thing isn't a real stand alone driver.  It is an errata
> fix that is specific to Freescale boards, and only is relevant in fixing
> magic SysRQ functionality on the serial console.   The Freescale boards
> are almost exclusively headless, with a serial console interface to
> u-boot as the only way to do initial interaction with the board at
> bootup.  So having serial as a module on these boards is largely
> academic.  (But if you want modular serial, you still can, and you
> dont need the errata fix for that.)
> 
> So, with all that in mind, I think this is the right fix.  I'll launch
> some build coverage against it, but it seems straightforward.  Thanks
> for the report, and sorry for catching pmac in the fallout.
> 
> Paul.
> ---
> 
>  From 675520f2d175bd71bf857b75a5a9b5a08ee0ee54 Mon Sep 17 00:00:00 2001
> From: Paul Gortmaker <paul.gortmaker@...driver.com>
> Date: Mon, 12 Dec 2011 21:18:15 -0500
> Subject: [PATCH] serial: make FSL errata depend on 8250_CONSOLE, not just
>  8250
> 
> The recent commit "serial: add irq handler for Freescale 16550 errata"
> would allow Kconfig choices that had 8250 support as a module and
> yet still try and build in the errata fix non-modular, resulting
> in build failures for some non-embedded PPC targets.
> 
> Since we hook in the errata fix from legacy_serial.c, which is
> built only for PPC_UDBG_16550, and since the errata is only really
> relevant for SysRQ on serial console, tighten up the dependencies
> to be exactly that.
> 
> We'll get coverage on the relevant Freescale boards because the
> Kconfig for their CPU types all select the PPC_UDBG_16550 option,
> and the defconfigs also all select the 8250_CONSOLE option.  Also,
> the 8250_CONSOLE option has a strict dependency on "SERIAL_8250=y"
> which resolves the reported problem for non Freescale targets.
> 
> Reported-by: Michael Neuling <mikey@...ling.org>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>

Works here for me (although it still seems like a Kconfig bug).

Tested-by: Michael Neuling <mikey@...ling.org>

> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index aa46993..5c46e90 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -99,7 +99,7 @@ config SERIAL_8250_PNP
>  
>  config SERIAL_8250_FSL
>  	bool
> -	depends on SERIAL_8250 && PPC
> +	depends on SERIAL_8250_CONSOLE && PPC_UDBG_16550
>  	default PPC
>  
>  config SERIAL_8250_HP300
> -- 
> 1.7.7
> 
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