linux-kernel - Re: [PATCH v3 15/22] firmware: arm_scmi: abstract mailbox interface

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Message-ID: <CABb+yY0DiDTKUkVrCDkx8_czfp2p6enzs7w_FRJpy91GDs9wXQ@mail.gmail.com>
Date:   Fri, 6 Oct 2017 19:04:13 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        ALKML <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Roy Franz <roy.franz@...ium.com>,
        Harb Abdulhamid <harba@...eaurora.org>,
        Nishanth Menon <nm@...com>, Loc Ho <lho@....com>,
        Alexey Klimov <alexey.klimov@....com>,
        Ryan Harkin <Ryan.Harkin@....com>
Subject: Re: [PATCH v3 15/22] firmware: arm_scmi: abstract mailbox interface

On Fri, Oct 6, 2017 at 6:57 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>
>
> On 06/10/17 12:34, Jassi Brar wrote:
>> On Wed, Oct 4, 2017 at 5:02 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>>
>>> Also, I have added shim only for specific controllers that need them.
>>> E.g. ARM MHU as Jassi disagreed to add doorbell mechanism to that.
>>> mbox_if provides default implementation that just calls direct mailbox
>>> APIs.
>>>
>> Yeah you could hack away the MHU driver to make your life easy at the
>> cost of duplicated code and extra DT bindings, but for a moment think
>> what if your development platform wasn't MHU but, say, Rockchip
>> mailbox controller?
>>
>
> As mentioned before I understand your concern. But the point is this
> needs to be replicated with each protocol on that controller.
>
Only generic protocols need to have a platform specific transport
layer. There's no escaping that.

> So as Arnd
> pointed out we can reduce that by generalizing common things like doorbell.
>
Rockchip, and most other controllers, has no "doorbell". And yet each
is perfectly capable of supporting SCMI.
Looking forward to your "generalised doorbell".