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SubjectRe: [PATCH 02/11] devicetree: bindings: Document Qualcomm cpus and enable-method
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On Nov 5, 2013, at 11:35 AM, Stephen Boyd wrote:

> On 11/05/13 09:12, Kumar Gala wrote:
>> On Nov 4, 2013, at 11:36 AM, Stephen Boyd wrote:
>>
>>> On 11/01, Rob Herring wrote:
>>>> On Fri, Nov 1, 2013 at 5:08 PM, Stephen Boyd <sboyd@codeaurora.org> wrote:
>>>>> From: Rohit Vaswani <rvaswani@codeaurora.org>
>>>>>
>>>>> Scorpion and Krait are Qualcomm cpus. These cpus don't use the
>>>>> spin-table enable-method. Instead they rely on mmio register
>>>>> accesses to enable power and clocks to bring CPUs out of reset.
>>>>>
>>>>> Cc: <devicetree@vger.kernel.org>
>>>>> Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
>>>>> [sboyd: Split off into separate patch, renamed method to
>>>>> qcom,mmio]
>>>>> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
>>>>> ---
>>>>>
>>>>> This slightly conflicts with my krait EDAC series.
>>>>>
>>>>> Documentation/devicetree/bindings/arm/cpus.txt | 3 +++
>>>>> 1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
>>>>> index 37258f9..e2969fa2 100644
>>>>> --- a/Documentation/devicetree/bindings/arm/cpus.txt
>>>>> +++ b/Documentation/devicetree/bindings/arm/cpus.txt
>>>>> @@ -44,6 +44,8 @@ For the ARM architecture every CPU node must contain the following properties:
>>>>> "marvell,mohawk"
>>>>> "marvell,xsc3"
>>>>> "marvell,xscale"
>>>>> + "qcom,scorpion"
>>>>> + "qcom,krait"
>>>>>
>>>>> And the following optional properties:
>>>>>
>>>>> @@ -52,6 +54,7 @@ And the following optional properties:
>>>>> different types of cpus.
>>>>> This should be one of:
>>>>> "spin-table"
>>>>> + "qcom,mmio"
>>>> Not exactly specific. How would you handle variations in the enable
>>>> method? The mmio method to enable is tied to the core type or SOC
>>>> type?
>>> Variations in the enable method are handled by searching for
>>> another node with different compatible strings. Later on in this
>>> series you'll see that we search for gcc-8660, kpss-acc-v1, or
>>> kpps-acc-v2. Once we find one of these nodes we perform the
>>> correct cold boot routine.
>>>
>>> I'm actually considering renaming this to "qcom,cold-boot". We
>>> could further extend the enable-metho property to allow
>>> "qcom,warm-boot" and then for cases like kexec we could make the
>>> enable method be warm boot and our smp code could be smart enough
>>> to know to skip the whole cold boot sequence.
>>
>> I think this should be more specific than just 'qcom,mmio' or 'qcom,warm-boot'. It should be 'qcom,kpss-acc-v1' or 'qcom-gcc-8660'.
>>
>
> Do you have any reasons why? I don't see why we need to keep adding more
> and more enable-methods every time the subsystem surrounding the CPU
> changes. The method is the same, write some registers to power up the
> CPU for the first time (cold boot) or ping the CPU to wake it up
> (warmboot). The only difference is where those registers live and a
> slight variation in the sequence that we perform.

By that argument every device could just be compatible with 'mmio' and be done with it ;)

As the registers you write vary, the compatible should vary.

- k
--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation



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