Re: [RFC][PATCH] bcmai: introduce AI driver

[RafaÅ MiÅecki]

W dniu 6 kwietnia 2011 22:57 uÅytkownik Michael BÃsch <mb@xxxxxxxxx> napisaÅ:
> On Wed, 2011-04-06 at 22:42 +0200, RafaÅ MiÅecki wrote:
>> 2011/4/6 RafaÅ MiÅecki <zajec5@xxxxxxxxx>:
>> > If we want to have two drivers working on two (different) cores
>> > simultaneously, we will have to add trivial mutex to group core
>> > switching with core operation (read/write).
>>
>> With a little of work we could avoid switching and mutexes on no-host
>> boards. MMIO is not limited to one core at once in such a case.
>
> I don't think that this is a problem at all.
> All that magic does happen inside of the bus I/O handlers.
> Just like SSB does it.
> From a driver point of view, the I/O functions just need to
> be atomic.
>
> For SSB it's not always 100% atomic, but we're always safe
> due to some assumptions being made. But this is an SSB implementation
> detail that is different from AXI. So don't look too closely
> at the SSB implementation of the I/O functions. You certainly want
> to implement them slightly differently in AXI. SSB currently doesn't
> make use of the additional sliding windows, because they are not
> available in the majority of SSB devices.
>
> The AXI bus subsystem will manage the sliding windows and the driver
> doesn't know about the details.

Sure, I've meant mutex inside bcmai (or whatever name), not on the driver side!

In BCMAI:
bcmai_read() {
mutex_get();
switch_core();
ioread();
mutex_release();
}

-- 
RafaÅ
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/