Thanks for working on these patches. We really need to get this stuff
merged and tested asap :)
On Tue, 18 Jul 2017 19:58:49 +0530
"Gautham R. Shenoy" <e...@linux.vnet.ibm.com> wrote:
> From: "Gautham R. Shenoy" <e...@linux.vnet.ibm.com>
>
>
> Currently we use the stop-api provided by the firmware to program the
> SLW engine to restore the values of hypervisor resources that get lost
> on deeper idle states (such as winkle). Since the deep states were
> only used for CPU-Hotplug on POWER8 systems, we would program the LPCR
> to have the PECE1 bit since Hotplugged CPUs shouldn't be spuriously
> woken up by decrementer.
>
> On POWER9, some of the deep platform idle states such as stop4 can be
> used in cpuidle as well. In this case, we want the CPU in stop4 to be
> woken up by the decrementer when some timer on the CPU expires.
>
> In this patch, for POWER9, we program the stop-api for LPCR with PECE1
> bit cleared only when we are offlining the CPU.
>
> Signed-off-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com>
> ---
> arch/powerpc/platforms/powernv/idle.c | 12 +++++++++++-
> arch/powerpc/platforms/powernv/smp.c | 28 ++++++++++++++++++++++++----
> 2 files changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/idle.c
> b/arch/powerpc/platforms/powernv/idle.c
> index 2abee07..f4a29d4 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -68,7 +68,7 @@ static int pnv_save_sprs_for_deep_states(void)
> * all cpus at boot. Get these reg values of current cpu and use the
> * same across all cpus.
> */
> - uint64_t lpcr_val = mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1;
> + uint64_t lpcr_val = mfspr(SPRN_LPCR);
> uint64_t hid0_val = mfspr(SPRN_HID0);
> uint64_t hid1_val = mfspr(SPRN_HID1);
> uint64_t hid4_val = mfspr(SPRN_HID4);
> @@ -85,6 +85,16 @@ static int pnv_save_sprs_for_deep_states(void)
> if (rc != 0)
> return rc;
>
> + /*
> + * On POWER8, the only state that uses SLW engine is
> + * winkle. This is only used for CPU-Hotplug. So we
> + * clear the decrementer bit from LPCR since we
> + * don't want to be woken up on decrementer when in
> + * winkle.
> + */
> + if (!cpu_has_feature(CPU_FTR_ARCH_300))
> + lpcr_val = lpcr_val & ~(u64)LPCR_PECE1;
> +
> rc = opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
> if (rc != 0)
> return rc;
> diff --git a/arch/powerpc/platforms/powernv/smp.c
> b/arch/powerpc/platforms/powernv/smp.c
> index 40dae96..5f2a712 100644
> --- a/arch/powerpc/platforms/powernv/smp.c
> +++ b/arch/powerpc/platforms/powernv/smp.c
> @@ -143,7 +143,8 @@ static void pnv_smp_cpu_kill_self(void)
> {
> unsigned int cpu;
> unsigned long srr1, wmask;
> -
> + uint64_t lpcr_val;
> + uint64_t pir;
> /* Standard hot unplug procedure */
> /*
> * This hard disables local interurpts, ensuring we have no lazy
> @@ -164,13 +165,17 @@ static void pnv_smp_cpu_kill_self(void)
> if (cpu_has_feature(CPU_FTR_ARCH_207S))
> wmask = SRR1_WAKEMASK_P8;
>
> + pir = get_hard_smp_processor_id(cpu);
> /* We don't want to take decrementer interrupts while we are offline,
> * so clear LPCR:PECE1. We keep PECE2 (and LPCR_PECE_HVEE on P9)
> * enabled as to let IPIs in.
> */
> - mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1);
> + lpcr_val = mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1;
> + mtspr(SPRN_LPCR, lpcr_val);
>
> while (!generic_check_cpu_restart(cpu)) {
> +
> +
> /*
> * Clear IPI flag, since we don't handle IPIs while
> * offline, except for those when changing micro-threading
> @@ -180,8 +185,15 @@ static void pnv_smp_cpu_kill_self(void)
> */
> kvmppc_set_host_ipi(cpu, 0);
>
> + /*
> + * If the CPU gets woken up by a special wakeup,
> + * ensure that the SLW engine sets LPCR with
> + * decrementer bit cleared, else we will get spurious
> + * wakeups.
> + */
> + if (cpu_has_feature(CPU_FTR_ARCH_300))
> + opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
Can you put these details into pnv_cpu_offline? Possibly even from there
into another special SPR save function? E.g.,
pnv_save_sprs_for_deep_state_decrementer_wakeup(bool decrementer_wakeup)
I'd like to put the LPCR manipulation for idle wake settings into idle.c
as well (pnv_cpu_offline), I think it fits better in there.
Thanks,
Nick
