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Subject: Re: [PATCH 3/3] powernv:idle: Set LPCR_UPRT on wakeup from deep-stop
From: Michael Neuling <mikey@neuling.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, "Aneesh Kumar K.V"
 <aneesh.kumar@linux.vnet.ibm.com>, "Gautham R. Shenoy"
 <ego@linux.vnet.ibm.com>,  Michael Ellerman <mpe@ellerman.id.au>, "Shreyas
 B. Prabhu" <shreyasbp@gmail.com>, Shilpasri G Bhat
 <shilpa.bhat@linux.vnet.ibm.com>, Vaidyanathan Srinivasan
 <svaidy@linux.vnet.ibm.com>, Anton Blanchard <anton@samba.org>, Balbir
 Singh <bsingharora@gmail.com>, Akshay Adiga
 <akshay.adiga@linux.vnet.ibm.com>,  Nicholas Piggin <npiggin@gmail.com>,
 Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Date: Thu, 13 Apr 2017 16:27:34 +1000
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On Thu, 2017-04-13 at 14:12 +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2017-04-13 at 09:28 +0530, Aneesh Kumar K.V wrote:
> > > =C2=A0 #endif
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0mtctr=C2=A0=C2=A0=C2=A0r12
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0bctrl
> > > +/*
> > > + * cur_cpu_spec->cpu_restore would restore LPCR to a
> > > + * sane value that is set at early boot time,
> > > + * thereby clearing LPCR_UPRT.
> > > + * LPCR_UPRT is required if we are running in Radix mode.
> > > + * Set it here if that be the case.
> > > + */
> > > +BEGIN_MMU_FTR_SECTION
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0mfspr=C2=A0=C2=A0=C2=A0r3, SPRN_LPCR
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0LOAD_REG_IMMEDIATE(r4, LPCR_UPRT)
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0or=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
r3, r3, r4
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0mtspr=C2=A0=C2=A0=C2=A0SPRN_LPCR, r3
> > > +END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)
>=20
> We are probably better off saving the value somewhere during boot
> and just "blasting" it whole back.

We seem to touch LPCR in a bunch of places these days.  Not sure when "some=
times
 during boot" should actually be.

Mikey