Re: [PATCH 00/13] uio_pruss: add support for devicetree and am33xx

[Andre Heider <a.heider@gmail.com>]

On Mon, Jul 07, 2014 at 05:50:09PM +0000, Paul Walmsley wrote:
> On Mon, 7 Jul 2014, Andre Heider wrote:
> 
> > On Sun, Jun 29, 2014 at 06:21:34PM +0200, Andre Heider wrote:
> > > 
> > > this series adds PRUv2 support to uio_pruss through devicetree, makes the
> > > device usable on am33xx and enables it on beaglebone black.
> > > Inspired by old patches from Matt Porter found in a downstream tree.
> > > 
> > > To archieve that this series:
> > > * adds a flag to omap_hwmod.c to get PRUSS out of hardreset (patch 5 and 6)
> 
> ...
> 
> > > * is the hardreset thing I did there the right thing to do? I think the
> > >   proper way would be a reset controller (which apparently doesn't yet exist
> > >   for this SoC?) and let the driver deassert/assert on probe/remove?
> > > * the platform device path has a clk_enable() / clk_put() calls. Are those
> > >   now redundant with the introduced pm_runtime_enable() pm_runtime_disable()
> > >   calls?
> 
> Probably you only need pm_runtime_{get,put}_*() calls, unless you're 
> changing clock parents or rates in your driver code.

No, the driver doesn't do that. So I can clean that up, nice.

> 
> > @OMAP guys: any comments? The series depends on patch 5 and 6; both touch
> > common hwmod code.
> 
> I'd suggest splitting the series into three independent pieces if 
> possible:
> 
> 1. UIO code, for the UIO maintainer(s)
> 2. DT pieces for Tony
> 3. hwmod pieces for me
> 
> That way they can be cleanly merged by the respective maintainers.
> 
> As far as the hwmod piece goes, I'd be willing to merge your code as a 
> temporary workaround for the issue, and marking it as such; but I'd be 
> concerned about power management-related interactions (i.e., does the 
> PRUSS need to be reset upon return from deep idle states, etc.)

Alright, thanks Paul.

About the deep idle states... I'm not sure, I couldn't find any explicit
wording about it in the am335x technical reference manual nor in in the
boneblack system reference manual.

According to the TRM the PRUSS lies in the PD_PER power domain, which is
powered down for the "Deepsleep0" power mode. So I *guess* the PRUSS also
needs to be taken out of hard reset when waking up from such a state.

But there's no upstream support for these power modes on am33xx anyway,
and I'd assume that HWMOD_INIT_DEASSERT_HARD_RESET gets removed or
replaced once that lands. Which is probably what you meant by "temporary".
FWIW, I'd be willing to look into that when the time comes and PRUSS gets
left behind.

Thanks,
Andre