Re: [PATCH v2 2/6] Documentation: devicetree: add bindings to support ARM MHU doorbells

From: Sudeep Holla
Date: Thu Jul 06 2017 - 05:33:42 EST

On 06/07/17 10:27, Jassi Brar wrote:
> On Thu, Jul 6, 2017 at 2:48 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>> Hi Jassi,
>> On 06/07/17 07:28, Jassi Brar wrote:
>>> On Wed, Jul 5, 2017 at 11:32 PM, Sudeep Holla <sudeep.holla@xxxxxxx> 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. Also can you please
answer other questions I had on mailbox API and not breaking SCPI
exiting users ? I need your suggestion to proceed on that. Similar to
SCPI, SCMI will be used by other platforms which must have doorbell
mailbox mechanism.