linux-kernel - Re: [RFC][PATCH 1/3] ARM: dts: vf610: Add Freescale FlexTimer Module timer node.

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Message-ID: <20140417082228.GA22160@dragon>
Date:	Thu, 17 Apr 2014 16:22:34 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>
CC:	Shawn Guo <shawn.guo@...aro.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Jingchang Lu <jingchang.lu@...escale.com>,
	"Jason.Jin@...escale.com" <Jason.Jin@...escale.com>,
	"Dongsheng.Wang@...escale.com" <Dongsheng.Wang@...escale.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 1/3] ARM: dts: vf610: Add Freescale FlexTimer Module
 timer node.

On Thu, Apr 17, 2014 at 07:49:31AM +0000, Li.Xiubo@...escale.com wrote:
> > > +			ftm0: ftm@...38000 {
> > > +				compatible = "fsl,vf610-ftm-timer";
> > > +				reg = <0x40038000 0x2000>;
> > > +				interrupts = <0 42 IRQ_TYPE_LEVEL_HIGH>;
> > > +				clock-names = "ftm0", "ftm1",
> > > +					"ftm0_counter_en", "ftm1_counter_en";
> > > +				clocks = <&clks VF610_CLK_FTM0>,
> > > +					<&clks VF610_CLK_FTM1>,
> > > +					<&clks VF610_CLK_FTM0_EXT_FIX_EN>,
> > > +					<&clks VF610_CLK_FTM1_EXT_FIX_EN>;
> > > +				status = "disabled";
> > 
> > For such completely internal block which has no pins route out on board,
> > we should probably just not have this "disabled" status line.
> > 
> 
> Well, from IEEE 1275, there defined a standard 'status' property indicating
> The operational status of one device. The 'status' property has four possible
> values: 'okay/ok', 'disabled', 'fail' and 'fail-xxx'.
> 
> If it is absent, that means the status of the device is unknown or okay.

Yes, missing 'disabled' status equals to a 'okay' status from Linux
implementation.  Then, the device is always available in device tree,
and Linux Kconfig option will control whether the driver for the device
is enabled.

> 
> If discard the status line here in vf610.dtsi, this device will be enabled
> as default though 'no pins route out' on the board, and actually there has
> pins route out on the board, as timer devices here we just not use it, but
> as PWM devices the pins will be used.
> 
> How about let the node disabled in vf610.dtsi, and then enable it in vf610-twr.dts
> if it will be used in TWR board... ?

Okay.  If there is some use cases that have board level configuration
like pin out, I'm fine with your existing code.

Shawn

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