linux-kernel - RE: [PATCHv6 1/4] pwm: Add Freescale FTM PWM driver support

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Message-ID: <1DD289F6464F0949A2FCA5AA6DC23F828DD72F@039-SN2MPN1-011.039d.mgd.msft.net>
Date:	Fri, 29 Nov 2013 05:58:09 +0000
From:	Li Xiubo <Li.Xiubo@...escale.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Shawn Guo <Shawn.Guo@...escale.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"t.figa@...sung.com" <t.figa@...sung.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"rob@...dley.net" <rob@...dley.net>,
	"ian.campbell@...rix.com" <ian.campbell@...rix.com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Huan Wang <Huan.Wang@...escale.com>,
	Jingchang Lu <jingchang.lu@...escale.com>
Subject: RE: [PATCHv6 1/4] pwm: Add Freescale FTM PWM driver support

Hi Thierry,

Thanks for your detail comments.

> > +	switch (fpc->counter_clk_select) {
> > +	case VF610_CLK_FTM0:
> > +		reg |= FTMSC_CLKSYS;
> > +		break;
> > +	case VF610_CLK_FTM0_FIX_SEL:
> > +		reg |= FTMSC_CLKFIX;
> > +		break;
> > +	case VF610_CLK_FTM0_EXT_SEL:
> > +		reg |= FTMSC_CLKEXT;
> > +		break;
> > +	default:
> > +		break;
> > +	}
> > +	reg |= fpc->clk_ps;
> 
> And another one above this line.
> 
> > +	writel(reg, fpc->base + FTM_SC);
> 
> I think with the proper locking in place what you should do is increment
> counter_clk_enable only here. That makes avoids having to decrement the
> count on error.
> 
> Similarly in fsl_counter_clock_disable() you can postpone decrementing
> the count until the very end.
> 

As the other mails we have talked about this that there are 8 channels
supported, but they share the same counter clock source. So we need to
make sure that when one channel is calling fsl_counter_clock_disable()
it shouldn't disable the counter clock if any other channel is still
enabled. Similary in fsl_counter clock_enable().

This is why I set counter_clk_enable property here.


--
Best Regards,


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