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SubjectRe: [PATCH v2 2/6] Documentation: devicetree: add bindings to support ARM MHU doorbells
On Thu, Jul 6, 2017 at 3:03 PM, Sudeep Holla <> wrote:
> On 06/07/17 10:27, Jassi Brar wrote:
>> On Thu, Jul 6, 2017 at 2:48 PM, Sudeep Holla <> wrote:
>>> Hi Jassi,
>>> On 06/07/17 07:28, Jassi Brar wrote:
>>>> On Wed, Jul 5, 2017 at 11:32 PM, Sudeep Holla <> wrote:
>>>>> I have posted the SCMI patches now[1],
>>>> I wish I was CC'ed on that. Now LKML seems too busy to forward it.
>>> Yes, my mistake, I should have cc-ed you.
>>>>> please let me know how to get
>>>>> both SCPI and SCMI working together with different doorbell bits on the
>>>>> same channel.
>>>> You say in the cover letter :
>>>> "Let me begin admitting that we are introducing yet another protocol to
>>>> achieve same things as many existing protocols like ARM SCPI, TI SCI,
>>>> QCOM RPM, Nvidia Tegra BPMP, and so on"
>>>> So SCMI is supposed to replace SCPI, SCI, RPM and BPMP or SCMI is
>>>> to be used for future platforms.
>>>> If SCPI and SCMI achieve the same, why have them both active simultaneously?
>>> Yes it may not be used, but the firmware might support both for backward
>>> compatibility. E.g. on Juno, we still may continue supporting SCPI while
>>> we transition to SCMI. So both old and new DTs must work.
>> Sure, but still there is no reason to have both SCMI and SCPI active
>> during _runtime_.
>> Either SCMI or SCPI should be populated by DT, not both.
>>>> Assuming there really is some sane excuse :-
>>> Yes as I mentioned above.
>> If you specify only one of SCPI/SCMI, you wouldn't need the shim arbitrator.
> I said it *may not be used*, currently it is used.
SCPI provides more than what SCMI currently does - dvfs, clock, sensor.
I see no reason why you must have SCPI and SCMI both running.

And even then there is a solution - a shim arbitrator. Other
platforms, those share a channel, do that. No big deal.

BTW, I hope you realise that we need a 'transport layer' which will
be the platform specific glue between mailbox controller specifics and
the generic SCMI code.
I see your confusion in the form of some issues in the SCMI
implementation, please CC me on the next revision.


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