Re: [PATCH v2 07/13] mailbox: pcc: Always map the shared memory communication address

[Sudeep Holla <sudeep.holla@arm.com>]

On Tue, Mar 11, 2025 at 07:32:34PM +0800, lihuisong (C) wrote:
> 
> 在 2025/3/6 0:38, Sudeep Holla 写道:
> > Currently the shared memory communication address was mapped by the
> > mailbox client drivers leading to all sorts of inconsistencies.
> > 
> > It also has resulted in the inconsistent attributes used while mapping
> > the shared memory regions.
> > 
> > In order to remove/eliminate any issues, let us ensures the shared
> > memory address is always mapped and unmapped when the PCC channels are
> > requested and release.
> > 
> > We need to map them as the ACPI PCCT associates these shared memory
> > with each channel subspace and may need use the status or the flags in
> > the headers of those shared memory communication address regions to
> > manage the transport/channel.
> > 
> > Since there are no users of pcc_chan_ioremap() and also it is mapped
> > by default, we can stop exporting it and merge the functionality into
> > pcc_mbox_request_channel().
> There are two ioremap for the existing mbox client driver after this patch.
> The existing mbox client driver would not use this variable, and no one else
> uses it. So it is safe, right?

IIUC yes, it should be fine.

> Do we need to make a statement that the two iommaps have no impact on the
> existing mbox client drivers?

We can add one, but again it will be become obsolete once we change driver
to use this new mapping. That's why I didn't add it. We can merge all the
changes together if that is the concern. I am fine either way.

Thanks a lot for all the review and testing.

-- 
Regards,
Sudeep