linux-kernel - Re: Pinmux bindings proposal V2

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Date:	Tue, 31 Jan 2012 09:32:22 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Stephen Warren <swarren@...dia.com>,
	Dong Aisheng <dongas86@...il.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"Linus Walleij (linus.walleij@...aro.org)" <linus.walleij@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"Grant Likely (grant.likely@...retlab.ca)" 
	<grant.likely@...retlab.ca>,
	Thomas Abraham <thomas.abraham@...aro.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"Simon Glass (sjg@...omium.org)" <sjg@...omium.org>,
	"cjb@...top.org" <cjb@...top.org>,
	Dong Aisheng-B29396 <B29396@...escale.com>,
	"Sascha Hauer (s.hauer@...gutronix.de)" <s.hauer@...gutronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Pinmux bindings proposal V2

On Mon, Jan 30, 2012 at 09:20:42AM -0800, Tony Lindgren wrote:
> * Shawn Guo <shawn.guo@...aro.org> [120129 17:13]:
> > On Fri, Jan 27, 2012 at 09:05:45AM -0800, Tony Lindgren wrote:
...
> > > Wouldn't it be cleaner to just clk_get esdhc_clk during init, then
> > > do clk_set_rate on it to toggle the rates?
> > >  
> > It's not an init-time switch but run-time one.  That said,
> > sdhci_ops.set_clock will be called during run-time.
> 
> Right, basically you don't want to do clk_get or pinmux_get during
> runtime, you do that once one during init. Then do clk_set_rate or
> whaterver during runtime.
> 
> Is there anything stopping from implementing sdhci_ops.set_rate
> using clock framework and clk_set_rate in this case BTW?
>  
We are doing this exactly for clk, and trying to figure out how to
handle pinctrl here.  I do not see how we can do pinmux_get at
init-time and pinmux_set_whatever at run-time.  The pinmux API does
not work that way.

> > > > > So I'd rather stay out of random named states for
> > > > > the pins coming from device tree; If we still need them, they should
> > > > > be common bindings rather than things like "xyz_clock_hack".
> > > > > 
> > > > The binding defines the syntax, and I do not see the necessity to
> > > > force the particular state name, which is really pinctrl client
> > > > device specific.
> > > 
> > > Do you have some other custom pin state example other than the
> > > clock rate change example above?
> > > 
> > I have another case PM related.  To aggressively save power, the pins
> > configured for particular function during active mode need to be
> > muxed on gpio mode and output 0 in low-power mode.
> 
> OK, but basically only a small subset of pins of the total pins?
> 
Actually, all pins used by the block.

-- 
Regards,
Shawn
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