linux-kernel - Re: [PATCH] clocksource/drivers/fttmr010: fix set_next

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Date:   Thu, 20 Sep 2018 21:09:36 +0000
From:   Tao Ren <taoren@...com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Joel Stanley <joel@....id.au>, Andrew Jeffery <andrew@...id.au>
CC:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Christopher Covington <cov@...com>, Tian Fang <tfang@...com>
Subject: Re: [PATCH] clocksource/drivers/fttmr010: fix set_next_event handler

On 9/20/18, 8:46 AM, "Linus Walleij" <linus.walleij@...aro.org> wrote:
 
> Actually this is much more intuitive too, it is the typical way to handle
> a down-counting timer. Good catch!
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Thank you Linus for the quick review!
    
> Sorry for any cargo-cult programming on my part :/
> Would be nice to get a nod from the AST2400 users that this works
> for them too, so included them in the To: field.

Make sense. I actually booted up kernel on qemu-palmetto (ast2400) but I'm doubting if test is valid because it depends on how qemu emulates the hardware. It would be great if someone can help to verify the patch on physical ast2400.

> It actually would make kind of sense to restart the up-counting
> timer from zero and set match to whatever value is passed in
> as well, so I might send a patch for this. It's no regression though
> so no hurry with that.

I agree. Besides being more intuitive, timer overflow interrupt (when <cr + cycles> overflows) could also be avoided by resetting the counter.

Thanks,
Tao Ren