lkml.org 
[lkml]   [2017]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3 15/22] firmware: arm_scmi: abstract mailbox interface
From
Date


On 04/10/17 12:24, Arnd Bergmann wrote:
> On Thu, Sep 28, 2017 at 3:11 PM, Sudeep Holla <sudeep.holla@arm.com> wrote:
>> Some of the mailbox controller expects controller specific data in order
>> to implement simple doorbell mechanism as expected by SCMI specification.
>>
>> This patch creates a shim layer to abstract the mailbox interface so
>> that it can support any mailbox controller. It also provides default
>> implementation which maps to standard mailbox client APIs, so that
>> controllers implementing doorbell mechanism need not require any
>> additional layer.
>>
>> Cc: Arnd Bergmann <arnd@arndb.de>
>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>
> Another level? Now we have three levels of stacked mailboxes, with
> the highest level being the combined mailbox/memory, then the shim,
> and below it the hardware mailbox.
>
> Can you try to come up with a way to do this with fewer abstractions?
>

I completely agree with you. I was against this but Jassi recommended
this. I just wanted this SCMI to work with mailbox controllers that
support simple doorbell mechanism as specified in the specification but
Jassi disagrees with that.

> Maybe you could assume that the mailbox itself can take variable-length
> data packets, and then use the shim here for those that require
> something else?
>

As per SCMI specification, we pass all the data in shared memory and it
just expects to use a simple doorbell feature from hardware mailbox
controllers. It's done that way intentionally to avoid dependency on h/w
and we for sure will have variety of it and that defeats the purpose
of this standard specification.

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.

--
Regards,
Sudeep

\
 
 \ /
  Last update: 2017-10-04 13:32    [W:0.145 / U:0.152 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site