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SubjectRe: [PATCH 3/5] powernv:idle: Define idle init function for power8
Hi Nicholas,

On Fri, Jul 07, 2017 at 01:06:46AM +1000, Nicholas Piggin wrote:
> On Wed, 5 Jul 2017 22:08:14 +0530
> "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> wrote:
>
> > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> >
> > In this patch we define a new function named pnv_power8_idle_init().
> >
> > We move the following code from pnv_init_idle_states() into this newly
> > defined function.
> > a) That patches out pnv_fastsleep_workaround_at_entry/exit when
> > no states with OPAL_PM_SLEEP_ENABLED_ER1 are present.
> > b) Creating a sysfs control to choose how the workaround has to be
> > applied when a OPAL_PM_SLEEP_ENABLED_ER1 state is present.
> > c) Set ppc_md.power_save to power7_idle when OPAL_PM_NAP_ENABLED is
> > present.
> >
> > With this, all the power8 specific initializations are in one place.
> >
> > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> > ---
> > arch/powerpc/platforms/powernv/idle.c | 59 ++++++++++++++++++++++++-----------
> > 1 file changed, 40 insertions(+), 19 deletions(-)
> >
> > diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> > index a5990d9..c400ff9 100644
> > --- a/arch/powerpc/platforms/powernv/idle.c
> > +++ b/arch/powerpc/platforms/powernv/idle.c
> > @@ -564,6 +564,44 @@ static void __init pnv_power9_idle_init(void)
> > pnv_first_deep_stop_state);
> > }
> >
> > +
> > +static void __init pnv_power8_idle_init(void)
> > +{
> > + int i;
> > + bool has_nap = false;
> > + bool has_sleep_er1 = false;
> > + int dt_idle_states = pnv_idle.nr_states;
> > +
> > + for (i = 0; i < dt_idle_states; i++) {
> > + struct pnv_idle_state *state = &pnv_idle.states[i];
> > +
> > + if (state->flags & OPAL_PM_NAP_ENABLED)
> > + has_nap = true;
> > + if (state->flags & OPAL_PM_SLEEP_ENABLED_ER1)
> > + has_sleep_er1 = true;
> > + }
> > +
> > + if (!has_sleep_er1) {
> > + patch_instruction(
> > + (unsigned int *)pnv_fastsleep_workaround_at_entry,
> > + PPC_INST_NOP);
> > + patch_instruction(
> > + (unsigned int *)pnv_fastsleep_workaround_at_exit,
> > + PPC_INST_NOP);
> > + } else {
> > + /*
> > + * OPAL_PM_SLEEP_ENABLED_ER1 is set. It indicates that
> > + * workaround is needed to use fastsleep. Provide sysfs
> > + * control to choose how this workaround has to be applied.
> > + */
> > + device_create_file(cpu_subsys.dev_root,
> > + &dev_attr_fastsleep_workaround_applyonce);
> > + }
> > +
> > + if (has_nap)
> > + ppc_md.power_save = power7_idle;
> > +}
> > +
> > /*
> > * Returns 0 if prop1_len == prop2_len. Else returns -1
> > */
> > @@ -837,6 +875,8 @@ static int __init pnv_probe_idle_states(void)
> >
> > if (cpu_has_feature(CPU_FTR_ARCH_300))
> > pnv_power9_idle_init();
> > + else
> > + pnv_power8_idle_init();
> >
> > for (i = 0; i < dt_idle_states; i++) {
> > if (!pnv_idle.states[i].valid)
> > @@ -858,22 +898,6 @@ static int __init pnv_init_idle_states(void)
> > if (pnv_probe_idle_states())
> > goto out;
> >
> > - if (!(supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
> > - patch_instruction(
> > - (unsigned int *)pnv_fastsleep_workaround_at_entry,
> > - PPC_INST_NOP);
> > - patch_instruction(
> > - (unsigned int *)pnv_fastsleep_workaround_at_exit,
> > - PPC_INST_NOP);
>
> So previously this would run on POWER9 and patch out those branches.
> But POWER9 never runs that code, so no problem. Good cleanup.

And that's what I thought, but on checking the assembly code, I found
that pnv_fastsleep_workaround_at_exit is executed on POWER9. Will fix
this!

>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>

--
Thanks and Regards
gautham.

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