linux-kernel - Re: [RFC PATCH v2 06/14] m68k: amiga: Convert to clocksource API

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Date:   Tue, 20 Nov 2018 09:04:01 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     fthain@...egraphics.com.au
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>, schwab@...ux-m68k.org,
        Arnd Bergmann <arnd@...db.de>, schivers@....com.au,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        schmitzmic@...il.com, John Stultz <john.stultz@...aro.org>,
        linux-m68k@...ts.linux-m68k.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 06/14] m68k: amiga: Convert to clocksource API

On Mon, Nov 19, 2018 at 2:22 AM Finn Thain <fthain@...egraphics.com.au> wrote:

> Add a platform clocksource by adapting the existing arch_gettimeoffset
> implementation.
>
> Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
> Acked-by: Linus Walleij <linus.walleij@...aro.org>
> ---
> Changed since v1:
>  - Moved clk_total access to within the irq lock.

Came to think of it, Geert can probably answer to the use cases
for the CIAs in Linux: the Amiga CIA has two counters.

It would make sense to use one as a free-runing clocksource and
the other one as clock event. Then Linux is extremely happy
without any complex workarounds trying to use just one timer
for both jobs.

Is there some specific reason why we can't use both counters
like this, except for legacy? (I am thinking it would be an improvement
on top of Finn's series once they go in.)

Yours,
Linus Walleij