From: jon-hunter@ti•com (Jon Hunter)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC RESEND 1/4] arm/dts: OMAP: Add timer nodes
Date: Mon, 23 Jul 2012 10:24:27 -0500 [thread overview]
Message-ID: <500D6CAB.4030504@ti.com> (raw)
In-Reply-To: <500439A8.1050705@ti.com>
Hi Rob,
On 07/16/2012 10:56 AM, Jon Hunter wrote:
> Hi Rob,
>
> On 07/13/2012 09:15 PM, Rob Herring wrote:
>> On 07/13/2012 05:26 PM, Jon Hunter wrote:
>>> Add the 12 GP timers nodes present in OMAP3.
>>> Add the 11 GP timers nodes present in OMAP4.
>>>
>>> Add documentation for timer properties specific to OMAP.
>>>
>>> For each timer an alias is being added. The purpose for doing this is because
>>> the OMAP dmtimer driver uses an ID to distinguish between the different timer
>>> instances. For example, a timer can be requested by its ID. By adding an alias
>>> for each timer we can then use the function of_alias_get_id() to extract the
>>> ID for each timer from the alias name. The same method is used for the TTY
>>> serial devices. If it is preferred that such an alias is not added and there
>>> is a better way to pass an ID from device-tree let me know.
>>
>> I'm not sure this is really a good use of aliases. UARTs use aliases
>> because it is important that the UART number to tty number is known and
>> fixed. IIUC, as an example you are picking timer1 because it has
>> properties X, Y and Z. If so, then you should describe those h/w
>> properties within the timer nodes so you can pick which timer to use
>> based on it's h/w properties.
>
> Thanks for the feedback. What you suggest could definitely work for most
> timers. The only item that I would need to resolve here is the handling
> of system timers (ie. those used for clockevents and clocksource). These
> system timers (for OMAP) are reserved during early boot based upon the
> timer ID today and so this is before the actual main timer driver has
> been probed and all the attributes of the timers has been read for
> device-tree.
>
> One thought would be to move the reservation of the system timers out of
> the kernel and into device-tree itself. Then we query device tree on
> start-up to see which we should use. I am wondering if this could be a
> better use of alias? For example, say I want to use timer1 as my
> clockevent timer and so I could have an alias of ...
>
> alias {
> clockevent_timer = &timer1;
> }
>
> However, I am not sure if this is even correct, because there does not
> appear to be an API to search the aliases by name and return the
> phandle, just of_alias_get_id(). Alternatively, I could add another
> property called "ti,timer-clockevent" that is populated for the timer
> used as the clockevent timer.
Do you have any inputs on the above? Does it make sense to reserve timer
resources for kernel system timers in device-tree?
Cheers
Jon
next prev parent reply other threads:[~2012-07-23 15:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-13 22:26 [RFC RESEND 0/4] ARM: OMAP3+: Add device-tree support for timers Jon Hunter
2012-07-13 22:26 ` [RFC RESEND 1/4] arm/dts: OMAP: Add timer nodes Jon Hunter
2012-07-14 2:15 ` Rob Herring
2012-07-14 6:56 ` Paul Walmsley
2012-07-14 14:01 ` Rob Herring
2012-07-14 17:42 ` Paul Walmsley
2012-07-16 17:48 ` Paul Walmsley
[not found] ` <50010402.3050502@firmworks.com>
2012-07-14 16:37 ` Mis?use of aliases David Gibson
2012-07-14 17:07 ` Mitch Bradley
2012-07-15 7:39 ` David Gibson
2012-07-16 15:56 ` [RFC RESEND 1/4] arm/dts: OMAP: Add timer nodes Jon Hunter
2012-07-18 7:19 ` Tony Lindgren
2012-07-18 15:11 ` Jon Hunter
2012-07-23 15:24 ` Jon Hunter [this message]
2012-08-15 9:11 ` Vaibhav Hiremath
2012-08-16 15:04 ` Jon Hunter
2012-08-30 20:14 ` Tony Lindgren
2012-09-07 20:26 ` Jon Hunter
2012-09-07 20:56 ` Tony Lindgren
2012-09-07 21:16 ` Jon Hunter
2012-09-06 13:45 ` Rob Herring
2012-09-07 2:09 ` Jon Hunter
2012-07-13 22:26 ` [RFC RESEND 2/4] ARM: OMAP3: Dynamically disable secure timer nodes for secure devices Jon Hunter
2012-08-15 9:13 ` Vaibhav Hiremath
2012-08-16 16:57 ` Jon Hunter
2012-08-17 5:32 ` Hiremath, Vaibhav
2012-08-17 12:24 ` Jon Hunter
2012-08-24 15:56 ` Hiremath, Vaibhav
2012-07-13 22:26 ` [RFC RESEND 3/4] ARM: OMAP4: Add timer clock aliases for device-tree Jon Hunter
2012-07-13 22:26 ` [RFC RESEND 4/4] ARM: OMAP: Add DT support for timer driver Jon Hunter
2012-07-13 23:41 ` Paul Walmsley
2012-07-14 0:57 ` Jon Hunter
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