linux-kernel - Re: [PATCH] clk: Add PWM clock driver

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Message-ID: <20140927200122.19023.40310@quantum>
Date:	Sat, 27 Sep 2014 13:01:22 -0700
From:	Mike Turquette <mturquette@...aro.org>
To:	Thierry Reding <thierry.reding@...il.com>,
	Janusz Użycki <j.uzycki@...roma.com.pl>
Cc:	"Philipp Zabel" <p.zabel@...gutronix.de>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-pwm@...r.kernel.org
Subject: Re: [PATCH] clk: Add PWM clock driver

Quoting Thierry Reding (2014-09-23 01:51:31)
> On Wed, Sep 10, 2014 at 10:05:17PM +0200, Janusz Użycki wrote:
> > Hi,
> > 
> > http://patchwork.ozlabs.org/patch/359069/
> > https://lkml.org/lkml/2014/6/12/186
> > 
> > Will the patch ever included to linux-next?
> 
> I've never seen this patch before. From a quick look it doesn't seem
> like it would work as is, but the idea is certainly interesting. If
> somebody decides to continue work on it, please Cc me and the linux-pwm
> mailing list.

I just merged a gpio-controlled clock gate and I'm fine with a PWM clock
output.

Janusz, how are you testing the clock driver?

Regards,
Mike

> 
> > pwm_config()  API could be extended to support
> > not only period [ns] and duty [ns] time
> > but also frequency [Hz] and duty cycle fraction [1/1000?]
> > (instead of time in ns) as parameters.
> > Then  ns (rounded by pwm) to freq. conversion problem
> > inclk_pwm_recalc_rate() usingpwm_get_period()
> > could be avoided.
> > To extend the API pwm_config() can support
> > new flags forduty_ns and period_ns,
> > eg. PWM_DUTY_PERCENT and PWM_PERIOD_HZ.
> 
> Is that rounding really a problem? Also the PWM chips will most likely
> use the concept of period and duty-cycle internally anyway, so it will
> convert back from Hz/percentage to nanoseconds and fall victim to
> similar rounding effects.
> 
> Thierry
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