Re: [PATCH v3 16/22] firmware: arm_scmi: add arm_mhu specific mailbox interface

[Sudeep Holla]

On 06/10/17 14:47, Jassi Brar wrote:
> On Fri, Oct 6, 2017 at 7:02 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>>
>>
>> On 06/10/17 12:26, Jassi Brar wrote:
>>> On Wed, Oct 4, 2017 at 5:06 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>>>> On Thu, Sep 28, 2017 at 3:11 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>>>>> This patch adds ARM MHU specific mailbox interface for SCMI.
>>>>>
>>>>> Cc: Arnd Bergmann <arnd@xxxxxxxx>
>>>>> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
>>>>
>>>> This clearly needs an explanation why we need another driver.
>>>>
>>> Yes the patch needs explanation which is that we need a shim layer to
>>> map SCMI requests onto what the underlying controller expects. The
>>> alternative was to clone the controller driver (MHU now and others
>>> later when their platforms support SCMI) and pretend SCMI is the only
>>> client they are ever going to serve.
>>>
>>
>> Again that's not the point, doorbell is more common feature and that can
>> be supported. As SCMI expects doorbell feature in the specification, it
>> just need to support that class of controllers.
>>
> NO.  All SCMI expects is SHMEM and a signal reaching the other end.
> The signal mechanism need not necessarily be "doorbell".
> 

Agreed, but creating an abstraction ro do something as generic as
doorbell and writing shim layer for each controller to use SCMI also
sounds bad.

-- 
Regards,
Sudeep