linux-kernel - Re: [PATCH v2 0/6] mailbox: arm_mhu: add support for doorbell mode

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Date:   Thu, 25 May 2017 18:50:31 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Alexey Klimov <alexey.klimov@....com>
Subject: Re: [PATCH v2 0/6] mailbox: arm_mhu: add support for doorbell mode

On Thu, May 25, 2017 at 5:00 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>
>
> On 24/05/17 11:56, Jassi Brar wrote:
>> On Wed, May 24, 2017 at 3:46 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>>>
>>> Hi,
>>>
>>> This series adds doorbell support to ARM MHU mailbox controller driver.
>>> Since we need to callback the different client based on the doorbel bits
>>> triggered from the remote, we can manage with single channel for the set
>>> of 32 doorbells.
>>>
>>> Regards,
>>> Sudeep
>>>
>>> v1->v2:
>>>         - Removed the notion od subchannels
>>>         - Treat each bit in the MHU register as a doorbell and hence
>>>           different channel with respect to mailbox framework
>>>
>> Whatever happened to the endless explanations I gave you, how the MHU
>> driver already supports your usecase?
>>
>
> Yes but you didn't respond to my queries:
> 1. The client driver is generic and expects it to be doorbell like
>    mailbox controller. I am referring to SCMI which will be released
>    soon. We can't embed ARM MHU or any other mailbox controller info
>    into that.
>
If SCMI is to be usable over different platforms, there has to be 2
sub-parts of the SCMI - one platform agnostic high level protocol
implementation, and the other platform specific 'transport' layer
where actual message xfer is done.

For the Nth time:-
    The 'mssg' in mbox_send_message(struct mbox_chan *chan, void
*mssg) is platform specific. For MHU it is simple u32*, whereas for
other platform it will be like 'struct my_protocol_message *'

I can't make it any clearer.

> 2. How do we call multiple clients from mhu_irq ? I have Slot/bit 0
>    being used by SCPI protocol(already in mainline) and slot 1/2 or more
>    will be used by SCMI ?
>
Like other platforms do, have a common client that manages messages
to/from clients working on same channel.

> 3. We already have mailbox-sti.c which implements exactly the same logic
>    of doorbell. Why did you not push back to implement something like
>    arm_mhu.c then ? I am confused as why you are so particular in this
>    case ?
>
The way STI's controller works (or as I was told), it warrants that
design. I know MHU very well and I bet it needs no modification.

 I explained in more than one way how to use the current driver, but
you refuse to acknowledge. Then I offered to modify your code for you,
but you don't agree to that either. I am running out of ways to
respond and point you back to my old posts.