From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mason <slash.tmp@free.fr>
Subject: Re: [RFC/NOT FOR MERGING] HACK: add global/private timers for A9
Date: Thu, 04 Jun 2015 22:32:40 +0200
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To: Felipe Balbi <balbi@ti.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>, Shawn Guo <shawn.guo@linaro.org>, Russell King <linux@arm.linux.org.uk>, Arnd Bergmann <arnd@arndb.de>, Tony Lindgren <tony@atomide.com>, Linux OMAP <linux-omap@vger.kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>

On 04/06/2015 22:08, Felipe Balbi wrote:

> On Thu, Jun 04, 2015 at 11:46:59AM +0200, Mason wrote:
>> Also, check /proc/timer_list for a "Broadcast device". If you don't
>> define one, the TWD timers are set to periodic mode, with hrtimers
>> disabled.
> 
> Did you manage to turn global timer into Broadcast device ?

Disclaimer: I am a kernel noob, take everything I say with
a rock of salt.

As far as I can see, the global timer code doesn't handle
frequency changes, whereas the TWD code does.

Yet all these timers are clocked by PERIPHCLK, which is defined
as CPUCLK / N. So if a platform enables cpufreq, CPUCLK will
vary, meaning PERIPHCLK will vary. I don't see how the global
timer can work in that situation.

cf. also this recent thread:
http://thread.gmane.org/gmane.linux.kernel.cpufreq/15770

Regards.