From: jon-hunter@ti•com (Jon Hunter)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/3] ARM: OMAP2+: 32k-counter: Use hwmod lookup to check presence of 32k timer
Date: Mon, 9 Apr 2012 15:18:22 -0500 [thread overview]
Message-ID: <4F83440E.70502@ti.com> (raw)
In-Reply-To: <79CD15C6BA57404B839C016229A409A83184ABEF@DBDE01.ent.ti.com>
Hi Vaibhav,
On 04/09/2012 01:19 AM, Hiremath, Vaibhav wrote:
[...]
> Let me summarize it here again,
>
> Currently, the timer code is using config option CONFIG_OMAP_32K_TIMER,
> to choose between 32ksync counter and gptimer; it is compile time option.
> If user wants to use gptimer for HR ticks, he must build the kernel without
> CONFIG_OMAP_32K_TIMER option.
>
> AM335x family of devices doesn't have 32ksync_counter available, only option
> here is to use gptimer for kernel clocksource and clockevents.
>
> So in order to support, multi-omap build including devices like AM335x, we
> must get rid of this option CONFIG_OMAP_32K_TIMER, atleast from clocksource
> registration perspective.
>
> So that means, we need to have some mechanism to handle or detect available
> clocksource runtime. Options would be,
>
> - Use HWMOD to detect availability of 32ksync_counter, else fallback
> to gptimer. [This was my original patch]
>
> But this restricts the use of gptimer completely on omap architecture,
> where we have 32ksync counter module.
True, but we would always want to use the 32k timer if CONFIG_PM is
specified. So what I am saying is that if a device has a 32ksync timer
and CONFIG_PM is defined, we always want to use the 32ksync timer and a
gptimer should never be used.
So we should/must restrict the use of a gptimer is CONFIG_PM is enabled
for devices that have the 32ksync timer.
> - So the next solution is to still keep compile time option, so that user
> will get to use gptimer atleast just changing the kernel config option.
>
> But, still, this is going to be kernel rebuild.
>
> - Next option came up was, register both the timers and override using
> kernel parameter.
>
> This will work only if, both the timers run at same rate/frequency; since
> we have one more layer here setup_sched_clock(), which actually can be
> called only once.
>
> - Next option suggested by Santosh, is to use kernel parameter as in parse
> it early, to make decision on if user wants to override default
> clocksource (32ksync)
>
> This is something will work for us and solves all above issues.
What happens if PM is enabled? Can you still override the default? I
don't think this should be allowed for devices with a 32ksync timer.
Jon
next prev parent reply other threads:[~2012-04-09 20:18 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-19 14:28 [PATCH 0/3] ARM: OMAP1/2+: 32k-timer: Add hwmod lookup for 32k-timer Vaibhav Hiremath
2012-01-19 14:28 ` [PATCH 1/3] ARM: OMAP2+: 32k-counter: Use hwmod lookup to check presence of 32k timer Vaibhav Hiremath
2012-01-23 23:38 ` Kevin Hilman
2012-01-24 8:53 ` Hiremath, Vaibhav
2012-01-24 17:47 ` Kevin Hilman
2012-02-01 8:00 ` Hiremath, Vaibhav
2012-03-13 11:37 ` Ming Lei
2012-03-19 11:11 ` Hiremath, Vaibhav
2012-03-19 11:44 ` Ming Lei
2012-03-19 12:15 ` Santosh Shilimkar
2012-03-21 11:42 ` Hiremath, Vaibhav
2012-03-21 14:00 ` Shilimkar, Santosh
2012-03-28 14:16 ` Hiremath, Vaibhav
2012-03-28 14:20 ` Shilimkar, Santosh
2012-03-28 14:37 ` Hiremath, Vaibhav
2012-03-28 14:49 ` Shilimkar, Santosh
2012-03-30 6:34 ` Hiremath, Vaibhav
2012-03-30 7:41 ` Shilimkar, Santosh
2012-03-30 8:32 ` Hiremath, Vaibhav
2012-03-30 8:38 ` Santosh Shilimkar
2012-03-30 9:12 ` Hiremath, Vaibhav
2012-03-30 9:20 ` Shilimkar, Santosh
2012-03-30 9:28 ` Hiremath, Vaibhav
2012-03-30 9:42 ` Shilimkar, Santosh
2012-03-30 11:29 ` Hiremath, Vaibhav
2012-03-30 11:35 ` Santosh Shilimkar
2012-03-31 1:30 ` Ming Lei
2012-03-31 6:30 ` Shilimkar, Santosh
2012-03-31 8:39 ` Ming Lei
2012-03-31 19:10 ` Shilimkar, Santosh
2012-04-01 1:39 ` Ming Lei
2012-04-01 5:53 ` Shilimkar, Santosh
2012-04-02 18:35 ` Kevin Hilman
2012-04-03 5:50 ` Shilimkar, Santosh
2012-04-03 15:35 ` Hiremath, Vaibhav
2012-04-04 9:04 ` Shilimkar, Santosh
2012-04-04 10:39 ` Hiremath, Vaibhav
2012-04-05 9:36 ` Hiremath, Vaibhav
2012-04-05 9:52 ` Russell King - ARM Linux
2012-04-05 10:31 ` Hiremath, Vaibhav
2012-04-05 10:46 ` Santosh Shilimkar
2012-04-05 21:33 ` Kevin Hilman
2012-04-06 5:21 ` Hiremath, Vaibhav
2012-04-06 18:04 ` Tony Lindgren
2012-04-09 6:19 ` Hiremath, Vaibhav
2012-04-09 20:18 ` Jon Hunter [this message]
2012-04-10 5:42 ` Hiremath, Vaibhav
2012-04-10 8:44 ` Russell King - ARM Linux
2012-04-10 8:57 ` Santosh Shilimkar
2012-04-10 9:29 ` Russell King - ARM Linux
2012-04-10 9:51 ` Shilimkar, Santosh
2012-04-10 21:03 ` Jon Hunter
2012-04-11 1:00 ` Ming Lei
2012-04-11 7:47 ` Shilimkar, Santosh
2012-04-06 21:18 ` Kevin Hilman
2012-04-09 6:25 ` Hiremath, Vaibhav
2012-03-21 11:29 ` Hiremath, Vaibhav
2012-03-23 8:20 ` Ming Lei
2012-03-30 6:39 ` Hiremath, Vaibhav
2012-03-05 22:55 ` Tony Lindgren
2012-03-07 9:48 ` Hiremath, Vaibhav
2012-03-09 17:58 ` Hiremath, Vaibhav
2012-03-12 9:39 ` Felipe Balbi
2012-03-12 9:48 ` Hiremath, Vaibhav
2012-03-12 10:17 ` Felipe Balbi
2012-03-12 10:39 ` Hiremath, Vaibhav
2012-01-19 14:28 ` [PATCH 2/3] ARM: OMAP2/3: Add idle_st bits for ST_32KSYNC timer to prcm-common header Vaibhav Hiremath
2012-03-05 22:56 ` Tony Lindgren
2012-03-07 9:49 ` Hiremath, Vaibhav
2012-01-19 14:28 ` [PATCH 3/3] ARM: OMAP2+: hwmod data: Add 32k-sync timer data to hwmod database Vaibhav Hiremath
2012-01-23 8:47 ` [PATCH 0/3] ARM: OMAP1/2+: 32k-timer: Add hwmod lookup for 32k-timer Hiremath, Vaibhav
2012-03-05 22:57 ` Tony Lindgren
2012-03-07 9:50 ` Hiremath, Vaibhav
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