[PATCH v3 2/2] OMAP: IOMMU: add support to callback during fault handling

Guzman Lugo, Fernando wrote:

Hi,

Hi Fernando,

In OMAP4 the cortex M3 is a double core processor and as each core is
running they own version of the RTOS we threat them independently. So
our driver which controls the remote processor sees two processor but
both use the same iommu hw. When a iommu fault happens, at this
moment, it is consider as a faltal error and it is no managed to
recover and continue, instead a restart of the processor is needed, if
the fault happens in core0 we need to reset core1 too and vice versa.
if the iommu would support several user callbacks, we can register the
callback which resets core0 and also the callback which resets core1
and treat them as totally independent processors. Also we have an
error event notifier driver, which is only in charge of notifying
error events to userspace, so we would have multiple callbacks we
could do this

The original purpose of the patch, as far as I understand, is to allow
getting useful information for debugging purposes should an iommu fault
happen.

Also, I'm not sure it's necessarily a good idea to just go and reset
the M3 cores in case an iommu fault happens --- this is very probably a
grave bug in the software running on those M3s. It should be fixed
instead of just hiding it. There will be consequences to host side as
well, won't there?

iommu <---- register fault callback for error notify driver

instead of

iommu <--- register fault callback for remote processor driver
<----register fault event for error notify driver.

with that, we remove one dependency of the errornotify driver.

I suppose this is not in mainline?

Regards,

-- 
Sakari Ailus
sakari.ailus at maxwell.research.nokia.com