linux-kernel - Re: [PATCH v4 13/13] mips: cevt-r4k: Update the r4k-clockevent frequency in sync with CPU

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Message-ID: <20200522073014.GI7331@alpha.franken.de>
Date:   Fri, 22 May 2020 09:30:14 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        afzal mohammed <afzal.mohd.ma@...il.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 13/13] mips: cevt-r4k: Update the r4k-clockevent
 frequency in sync with CPU

On Thu, May 21, 2020 at 05:07:24PM +0300, Serge Semin wrote:
> Due to being embedded into the CPU cores MIPS count/compare timer
> frequency is changed together with the CPU clocks alteration.
> In case if frequency really changes the kernel clockevent framework
> must be notified, otherwise the kernel timers won't work correctly.
> Fix this by calling clockevents_update_freq() for each r4k clockevent
> handlers registered per available CPUs.
> 
> Traditionally MIPS r4k-clock are clocked with CPU frequency divided by 2.
> But this isn't true for some of the platforms. Due to this we have to save
> the basic CPU frequency, so then use it to scale the initial timer
> frequency (mips_hpt_frequency) and pass the updated value further to the
> clockevent framework.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> Cc: Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>
> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> Cc: Paul Burton <paulburton@...nel.org>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: devicetree@...r.kernel.org
> ---
>  arch/mips/kernel/cevt-r4k.c | 44 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]