Hi Matt,

On 2 October 2012 16:25, Matt Porter [off-list ref] wrote:
...

I can see why you went this path with the iommu driver as it already had
some integration code present here. I have some concerns going forward
about how this should be long-term. Take any platform booting only with
DT populated, we'd like to avoid having to use this approach where
platform private APIs are called via pdata. In fact, it's going to makes
thing ugly to carry any sort of pdata for a driver that's otherwise
driven exclusively from DT.

For AM335x, I can implement this approach, but it means adding some
pruss specific integration code just to have it create the pdata for
reset_name and assert/deassert.

Yes I agree, it looks a bit ugly for devices that have more than one
reset line name too, but right now there is no other way to keep the
reset names and also provide flexibility to the driver to control them
in a given order.

From reading all the threads on hardresets and OMAP, it seems we may not
be able to come up with a generic OMAP handler for these resets and
that's really reflected in the fact that this API exists. So given that,
it reasons that OMAP isn't the only one needing a reset API for drivers.
I'm thinking that (as trivial as it may seem), this support may need to
move to a reset subsystem such that drivers have a clean way to access
reset resources in an SoC.

Well, there was a point where the OMAP hwmod code contained the reset
code and at least for me it was working fine, with iommu and ipu
processor, just with a minor misleading warning print... however then
this code got stripped out and since there appeared to be people
needing to handle their reset lines in unknown ways it was advised
that everybody should implement their own reset functions, but in my
case I could reuse most of the disabled code at the expense of almost
duplicating _enable (omap_hwmod) function while waiting all the reset
line users started asking for changes.

I'm curious if you or others have thought about where this needs to go
next.

I haven't planned for a reset subsystem or a more generic
implementation, although I have been looking for a way to avoid using
the pdata function pointers.

When I first thought about a reset subsystem it seemed to trivial
to bother with but looking at the reasoning behind the power_seq
subsystem, it seems to have similar justification to get this machine
specific logic out of the platform code and under standardized control
of the driver.

IMHO, the reset code even if made a subsystem or a library, would
still need to interface with machine specific code and definitions
(say omap_hwmod), so I don't see much difference in making the
omap_device reset handlers as exported symbols for the time being,
with acceptance of the owners of omap_device code.

And then if power_seq makes it to mainline perhaps extending it to
handle deassert, assert and softreset events, but then again this
would have the same hooks to omap_hwmod which is the one with the prcm
information.

Regards,

Omar