linux-kernel - Re: [PATCH] pinctrl/pinconfig: add debug interface

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Message-ID: <20130211210041.GW4801@atomide.com>
Date:	Mon, 11 Feb 2013 13:00:42 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Stephen Warren <swarren@...dia.com>,
	Anmar Oueja <anmar.oueja@...aro.org>,
	Laurent Meunier <laurent.meunier@...com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] pinctrl/pinconfig: add debug interface

* Stephen Warren <swarren@...dotorg.org> [130211 12:57]:
> On 02/10/2013 01:11 PM, Linus Walleij wrote:
> > From: Laurent Meunier <laurent.meunier@...com>
> > 
> > This update adds a debugfs interface to modify a pin configuration
> > for a given state in the pinctrl map. This allows to modify the
> > configuration for a non-active state, typically sleep state.
> > This configuration is not applied right away, but only when the state
> > will be entered.
> > 
> > This solution is mandated for us by HW validation: in order
> > to test and verify several pin configurations during sleep without
> > recompiling the software.
> 
> I never understood why HW engineers can't just recompile the kernel.
> Besides, it's just a device tree change these days - no recompile even
> required, right?

Typically when bringing up a new board you do not have the driver
specific mux settings verified. For developers, it's easiest to tweak
the muxing during runtime do the drivers as a loadable module, then
export the verified mux configuration into a .dts file.

Regards,

Tony
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