Re: [PATCH] soc/tegra: Implement Tegra186 PMC support

[Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On Thu, Nov 17, 2016 at 05:40:35PM +0000, Sudeep Holla wrote:
> 
> 
> On 17/11/16 17:31, Thierry Reding wrote:
> > On Thu, Nov 17, 2016 at 05:28:53PM +0000, Sudeep Holla wrote:
> > > 
> > > 
> > > On 17/11/16 17:16, Thierry Reding wrote:
> > > > From: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> > > > 
> > > > The power management controller on Tegra186 has changed in backwards-
> > > > incompatible ways with respect to earlier generations. This implements a
> > > > new driver that supports inversion of the PMU interrupt as well as the
> > > > "recovery", "bootloader" and "forced-recovery" reboot commands.
> > > > 
> > > > Signed-off-by: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> > > > ---
> > > >  .../bindings/arm/tegra/nvidia,tegra186-pmc.txt     |  34 +++++
> > > >  drivers/soc/tegra/Makefile                         |   2 +-
> > > >  drivers/soc/tegra/pmc-tegra186.c                   | 169 +++++++++++++++++++++
> > > >  3 files changed, 204 insertions(+), 1 deletion(-)
> > > >  create mode 100644 Documentation/devicetree/bindings/arm/tegra/nvidia,tegra186-pmc.txt
> > > >  create mode 100644 drivers/soc/tegra/pmc-tegra186.c
> > > > 
> > > 
> > > [...]
> > > 
> > > > diff --git a/drivers/soc/tegra/pmc-tegra186.c b/drivers/soc/tegra/pmc-tegra186.c
> > > > new file mode 100644
> > > > index 000000000000..ee28eddd8e3c
> > > > --- /dev/null
> > > > +++ b/drivers/soc/tegra/pmc-tegra186.c
> > > 
> > > [...]
> > > 
> > > > +
> > > > +	/*
> > > > +	 * If available, call the system restart implementation that was
> > > > +	 * registered earlier (typically PSCI).
> > > > +	 */
> > > > +	if (pmc->system_restart) {
> > > > +		pmc->system_restart(reboot_mode, cmd);
> > > > +		return NOTIFY_DONE;
> > > > +	}
> > > > +
> > > 
> > > IIUC, Tegra186 implements PSCI v1.0 and it always takes above path.
> > > So what other platforms does this driver support ? The name is
> > > pmc-tegra186.c, hence the confusion.
> > 
> > It's technically possible to run Tegra186 without PSCI enabled, or even
> > boot it with firmware that doesn't implement PSCI. In such cases it
> 
> OK, with enable-method as "spin-table" I suppose ?

Yes, that would probably be the other choice for SMP.

> > would be nice to still be able to reboot via the PMC code above.
> 
> I assume it's only for development purposes as you won't have much CPU
> power management support without PSCI.

This is what I had primarily in mind. Sometimes it might be useful to
boot without PSCI at all (as a poor man's way of disable SMP), in which
case this driver can still be used for reboot into the bootloader or
recovery mode.

Thierry

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