linux-kernel - Re: [PATCHv2 1/4] Documentation: Add memory mapped ARM architected timer binding

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Date:	Thu, 25 Apr 2013 11:35:12 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Rob Herring <robherring2@...il.com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 1/4] Documentation: Add memory mapped ARM architected
 timer binding

Rob,

Can I get your ack on this binding or do you think we need to change
something?

Thanks,
Stephen

On 04/15/13 14:33, Stephen Boyd wrote:
> On 04/15/13 14:20, Rob Herring wrote:
>> On Fri, Apr 12, 2013 at 7:27 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
>>> @@ -26,3 +30,52 @@ Example:
>>>                              <1 10 0xf08>;
>>>                 clock-frequency = <100000000>;
>>>         };
>>> +
>>> +** Memory mapped timer node properties
>>> +
>>> +- compatible : Should at least contain "arm,armv7-timer-mem".
>> Everything about this timer is architecturally defined? If not, let's
>> use a more specific name.
> I'm not sure I'm following you, but everything described here is part of
> the ARM definition. What would be a more specific name?
>
>>> +
>>> +- clock-frequency : The frequency of the main counter, in Hz. Optional.
>>> +
>>> +- reg : The control frame base address.
>>> +
>>> +Note that #address-cells, #size-cells, and ranges shall be present to ensure
>>> +the CPU can address a frame's registers.
>>> +
>>> +Frame:
>>> +
>>> +- frame-number: 0 to 7.
>> I'd really like to get rid of the frame numbers and sub-nodes. Is the
>> frame number significant to software?
> We need the frame number to read and write registers in the control
> frame (the first base in the parent node). We currently use it to
> determine if a frame has support for the virtual timer by reading the
> CNTTIDR (a register with 4 bits per frame describing capabilities). If
> we wanted to control access to the second view of a frame we would also
> need to configure the CNTPL0ACRn register that pertains to the frame
> we're controlling. Without a frame number we wouldn't know which
> register to write.
>
>>> +- interrupts : Interrupt list for physical and virtual timers in that order.
>>> +  The virtual timer interrupt is optional.
>> Is that optional per frame?
> Yes the virtual and physical timer interrupt is per-frame and the
> virtual interrupt is optional.
>


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