From: Mason <slash.tmp@free.fr>
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>
Subject: Re: [RFC/NOT FOR MERGING] HACK: add global/private timers for A9
Date: Thu, 04 Jun 2015 22:32:40 +0200 [thread overview]
Message-ID: <5570B5E8.90300@free.fr> (raw)
In-Reply-To: <20150604200850.GF5710@saruman.tx.rr.com>
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.
WARNING: multiple messages have this Message-ID (diff)
From: slash.tmp@free.fr (Mason)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC/NOT FOR MERGING] HACK: add global/private timers for A9
Date: Thu, 04 Jun 2015 22:32:40 +0200 [thread overview]
Message-ID: <5570B5E8.90300@free.fr> (raw)
In-Reply-To: <20150604200850.GF5710@saruman.tx.rr.com>
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.
next prev parent reply other threads:[~2015-06-04 20:32 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-03 20:32 [RFC/NOT FOR MERGING] HACK: add global/private timers for A9 Felipe Balbi
2015-06-03 20:32 ` Felipe Balbi
2015-06-03 20:44 ` Tony Lindgren
2015-06-03 20:44 ` Tony Lindgren
2015-06-03 20:55 ` Arnd Bergmann
2015-06-03 20:55 ` Arnd Bergmann
2015-06-03 21:04 ` Felipe Balbi
2015-06-03 21:04 ` Felipe Balbi
2015-06-03 21:28 ` Felipe Balbi
2015-06-03 21:28 ` Felipe Balbi
2015-06-03 21:41 ` Stephen Boyd
2015-06-03 21:41 ` Stephen Boyd
2015-06-03 21:54 ` Felipe Balbi
2015-06-03 21:54 ` Felipe Balbi
2015-06-04 9:46 ` Mason
2015-06-04 9:46 ` Mason
2015-06-04 19:05 ` Felipe Balbi
2015-06-04 19:05 ` Felipe Balbi
2015-06-04 20:08 ` Felipe Balbi
2015-06-04 20:08 ` Felipe Balbi
2015-06-04 20:18 ` Felipe Balbi
2015-06-04 20:18 ` Felipe Balbi
2015-06-04 20:29 ` Felipe Balbi
2015-06-04 20:29 ` Felipe Balbi
2015-06-04 22:20 ` Stephen Boyd
2015-06-04 22:20 ` Stephen Boyd
2015-06-05 15:42 ` Felipe Balbi
2015-06-05 15:42 ` Felipe Balbi
2015-06-04 20:32 ` Mason [this message]
2015-06-04 20:32 ` Mason
2015-06-04 20:37 ` Felipe Balbi
2015-06-04 20:37 ` Felipe Balbi
2015-06-04 21:00 ` Mason
2015-06-04 21:00 ` Mason
2015-06-04 21:46 ` Tony Lindgren
2015-06-04 21:46 ` Tony Lindgren
2015-06-03 22:26 ` Tony Lindgren
2015-06-03 22:26 ` Tony Lindgren
2015-06-04 3:45 ` Felipe Balbi
2015-06-04 3:45 ` Felipe Balbi
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