linux-kernel - Re: [PATCH 46/58] clocksource/drivers: Add a new driver for the Atmel ARM TC blocks

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Message-ID: <20170607231139.5dgzu3tc4lmuj43y@piout.net>
Date:   Thu, 8 Jun 2017 01:11:39 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 46/58] clocksource/drivers: Add a new driver for the
 Atmel ARM TC blocks

On 07/06/2017 at 23:38:10 +0200, Daniel Lezcano wrote:
> On Wed, Jun 07, 2017 at 05:09:08PM +0200, Alexandre Belloni wrote:
> I suggest to look what is in 'lot-of-things()' and especially what is doing
> regcache_read().
> 

I know it does a lot...

> May be you can reconsider the regmap? This driver is the only one use the
> regmap AFAICT and I don't think it is adequate.
> 

That is not true, I also converted the PWM driver and both a capture and
qdec drivers are coming.



> > > > > Can you explain why we have two clocks here?
> > > > > 
> > > > 
> > > > Each channel have its clock, I can add a comment if you want.
> > > 
> > > I don't understand. Why do we have two clocks?
> > > 
> > > One channel is driven by one clock and the second one takes the overflow signal
> > > from the first one, so no second clock is involved there, no?
> > > 
> > 
> > Those are the peripheral clocks, they are not used by the counters but
> > used to be able to read/write the registers.
> 
> Mmh, strange. Why is the clk[0]'s rate used in this case?
> 

That's abusing the fact that is has the same rate as the clock feeding
the counter.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com