Re: [PATCH 13/13] mailbox: omap: Remove kernel FIFO message queuing

[Andrew Davis]

On 4/1/24 6:39 PM, Hari Nagalla wrote:
> On 3/25/24 12:20, Andrew Davis wrote:
> > The kernel FIFO queue has a couple issues. The biggest issue is that
> > it causes extra latency in a path that can be used in real-time tasks,
> > such as communication with real-time remote processors.
> >
> > The whole FIFO idea itself looks to be a leftover from before the
> > unified mailbox framework. The current mailbox framework expects
> > mbox_chan_received_data() to be called with data immediately as it
> > arrives. Remove the FIFO and pass the messages to the mailbox
> > framework directly.
> Yes, this would definitely speed up the message receive path. With RT linux, the irq runs in thread context, so that is Ok. But with non-RT the whole receive path runs in interrupt context. So, i think it would be appropriate to use a threaded_irq()?

I was thinking the same at first, but seems some mailbox drivers use threaded, others
use non-threaded context. Since all we do in the IRQ context anymore is call
mbox_chan_received_data(), which is supposed to be IRQ safe, then it should be fine
either way. So for now I just kept this using the regular IRQ context as before.

If that does turn out to be an issue then let's switch to threaded.

Andrew