On Wed, Apr 01, 2020 at 01:12:37AM +0000, Peng Fan wrote:
> Hi Sudeep,
>
> > Subject: [PATCH 1/4] firmware: arm_scmi: Make mutex channel specific
> >
> > In order to support multiple SMC/HVC transport channels with associated
> > shared memory,
>
> Does this mean each channel will have its own shared memory? Or
> All channels share the same shared memory?
>
It depends on platform firmware and DT. If there is only one shmem at
the top level scmi node, all share that single channel. If some/all
protocols have their own channel, they there must be shmem entry in the
corresponding child node.
> it is better to maintain the mutex per channel instead of
> > existing global one.
>
> If all channels shared the same memory, use per channel mutex lock
> will not be able to prevent other channels accessing shared memory
> at the same time.
>
No we don't create channel per protocol. If they share, we just share
the channel pointer. Look at:
if (!info->desc->ops->chan_available(dev, idx)) {
cinfo = idr_find(idr, SCMI_PROTOCOL_BASE);
if (unlikely(!cinfo)) /* Possible only if platform has no Rx */
return -EINVAL;
goto idr_alloc;
}
If a protocol doesn't have a dedicated channel, we just assign the base
protocol channel to it. We don't call chan_setup at all on that channel.
Your patch assumed so but the core driver never did that.
Hope this clarifies you doubt.
--
Regards,
Sudeep
