Re: [PATCH v10 1/1] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule <ashwin.chaugule@linaro.org>]

On 12 November 2014 08:32, Sudeep Holla <sudeep.holla@arm.com> wrote:
>
>
> On 11/11/14 20:25, Arnd Bergmann wrote:
>>
>> On Tuesday 11 November 2014 15:01:28 Sudeep Holla wrote:
>>>
>>> On 11/11/14 13:18, Ashwin Chaugule wrote:
>>>>
>>>> On 11 November 2014 05:30, Sudeep Holla <sudeep.holla@arm.com> wrote:
>>>>>
>>>>> On 07/11/14 14:52, Ashwin Chaugule wrote:
>>>>
>>>> The IRQ part of the spec seems to be under discussion (single irq per
>>>> subspace / common IRQ across all) and as you may be aware we're
>>>> working on trying it out on Juno. That'll guide the design. What I
>>>> have here is good enough to start off with and has been tested. I dont
>>>> think we should have a problem using the mailbox API for asyn tx
>>>> though, but I'd really^n prefer if we get something out there first.
>>>>
>>>
>>> That's the different and still under discussion. But you need to support
>>> Type 1 subspace as it stands in ACPI v5.1
>>
>>
>> Why? We should only implement whatever is required to support existing
>> hardware,
>> not because something is in the spec.
>
>
> Agreed. I assumed that this was tested on some hardware which adhere to
> Type 1 subspace of the spec and I asked to implement interrupt mode as
> it is always better compared to polling mode and current spec. has
> support for the interrupts.

I do not have hardware to test the IRQ parts as of now, so the plan
was to at least get polling mode out there. That will enable a lot of
folks and will be useful as a fallback mode later on as well. We can
add IRQ mode stuff once it is tested. I dont see the point in
supporting it all from the start.

>
> Also, the existing Type1 is not sufficient for the mailbox/PCC on Juno
> platform, hence the new proposal.

Just as Juno is proving that the IRQ mode in the current spec is
insufficient, we may find similar issues with other hardware as it
becomes available. It makes more sense to tackle this once we have
some hardware to test this part of PCC properly. Just because its in
the spec doesn't mean its right. ;)

Btw, if you or anyone has any hardware to test it on, patches are more
than welcome. :)

Thanks,
Ashwin