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

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Date:   Wed, 7 Jun 2017 17:27:50 +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 16:17:35 +0200, Daniel Lezcano wrote:
> > You mean you don't like how it is used? Or you don't think having the
> > timer full name is useful?
> 
> The field is not needed, the only place where it is used is where we affect it.
>  

It is used in tcb_clksrc_register:

tc.clksrc.name = tc.name;

> > The main reason is that RobH doesn't want to have the use (clocksource
> > or clockevent) of the timer in the DT so when probing a timer, I need to
> > know whether I already have a clocksource to decide when it is time to
> > register a clockevent.
> 
> Yes, we had this discussion some weeks ago.
> 
> This registered hack forces the DT to define first the clocksource, then the
> clockevent.
> 
> So, I suggest you fold the timer definition into a single one like the other
> drivers.

I was going to agree but this is not flexible enough because the
quadrature decoder always uses the first two channels. So on some
products, we may have:
 - TCB0:
   o channels 0,1: qdec
   o channel 2: clocksource

 - TCB1:
   o channels 0,1: qdec
   o channel 2: clockevent

This avoids wasting TCB channels.

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