RE: [PATCH V2] firmware: arm_scmi: Make scmi core independent of transport type

Subject: Re: [PATCH V2] firmware: arm_scmi: Make scmi core independent of
transport type

On Tue, Jan 14, 2020 at 12:11 PM Viresh Kumar [off-list ref]
wrote:

quoted

On 14-01-20, 10:56, Arnd Bergmann wrote:

quoted

My point was that you cannot mix __iomem accesses with pointer
accesses. As I understood it, the current version uses a pointer to
a

The current version is stupid as I misunderstood the whole __iomem
thing and just dropped it :)

quoted

hardware mailbox with structured data, so you have to use ioremap()
to get a token you can pass into ioread(), but (some of) the new
transport types would just be backed by regular RAM, on which this
is not a well-defined operation and you have to use memremap() and
memcpy() instead.

Okay, I think I understand that a bit now. So here are the things
which I may need to do now:

- Maybe move payload to struct scmi_mailbox structure, as that is the
  transport dependent structure..

- Do ioremap, etc in mailbox.c only instead of driver.c

- Provide more ops in struct scmi_transport_ops to provide read/write
  helpers to the payload and implement the ones based on
  ioread/iowrite in mailbox.c ..

Am I thinking in the right direction now ?

That sounds about right. What I'm still not sure about is whether the current
kernel code is actually correct and should use iomeap() in the first place. Can
you confirm that all current hardware implementations actually use MMIO
type registers here rather than just rely on a buffer in RAM?

i.MX8(alought not use SCMI) use MU(message unit) to transfer data between
Acore and Mcore firmware, not using shared memory.

Thanks,
Peng.

      Arnd

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