From e1c1cfed54326fd2b17c78f0c85092167fc0783b Mon Sep 17 00:00:00 2001 From: "Gautham R. Shenoy" Date: Fri, 21 Jul 2017 16:11:37 +0530 Subject: [PATCH] powerpc/powernv: Save/Restore additional SPRs for stop4 cpuidle The stop4 idle state on POWER9 is a deep idle state which loses hypervisor resources, but whose latency is low enough that it can be exposed via cpuidle. Until now, the deep idle states which lose hypervisor resources (eg: winkle) were only exposed via CPU-Hotplug. Hence currently on wakeup from such states, barring a few SPRs which need to be restored to their older value, rest of the SPRS are reinitialized to their values corresponding to that at boot time. When stop4 is used in the context of cpuidle, we want these additional SPRs to be restored to their older value, to ensure that the context on the CPU coming back from idle is same as it was before going idle. In this patch, we define a SPR save area in PACA (since we have used up the volatile register space in the stack) and on POWER9, we restore SPRN_PID, SPRN_LDBAR, SPRN_FSCR, SPRN_HFSCR, SPRN_MMCRA, SPRN_MMCR1, SPRN_MMCR2 to the values they had before entering stop. Signed-off-by: Gautham R. Shenoy Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/cpuidle.h | 11 +++++ arch/powerpc/include/asm/paca.h | 7 ++++ arch/powerpc/kernel/asm-offsets.c | 8 ++++ arch/powerpc/kernel/idle_book3s.S | 65 +++++++++++++++++++++++++++++- 4 files changed, 89 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h index 52586f9956bb..8a174cba5567 100644 --- a/arch/powerpc/include/asm/cpuidle.h +++ b/arch/powerpc/include/asm/cpuidle.h @@ -67,6 +67,17 @@ #define ERR_DEEP_STATE_ESL_MISMATCH -2 #ifndef __ASSEMBLY__ +/* Additional SPRs that need to be saved/restored during stop */ +struct stop_sprs { + u64 pid; + u64 ldbar; + u64 fscr; + u64 hfscr; + u64 mmcr1; + u64 mmcr2; + u64 mmcra; +}; + extern u32 pnv_fastsleep_workaround_at_entry[]; extern u32 pnv_fastsleep_workaround_at_exit[]; diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h index dc88a31cc79a..04b60af027ae 100644 --- a/arch/powerpc/include/asm/paca.h +++ b/arch/powerpc/include/asm/paca.h @@ -31,6 +31,7 @@ #endif #include #include +#include register struct paca_struct *local_paca asm("r13"); @@ -183,6 +184,12 @@ struct paca_struct { struct paca_struct **thread_sibling_pacas; /* The PSSCR value that the kernel requested before going to stop */ u64 requested_psscr; + + /* + * Save area for additional SPRs that need to be + * saved/restored during cpuidle stop. + */ + struct stop_sprs stop_sprs; #endif #ifdef CONFIG_PPC_STD_MMU_64 diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 6e95c2c19a7e..8cfb20e38cfe 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -746,6 +746,14 @@ int main(void) OFFSET(PACA_SUBCORE_SIBLING_MASK, paca_struct, subcore_sibling_mask); OFFSET(PACA_SIBLING_PACA_PTRS, paca_struct, thread_sibling_pacas); OFFSET(PACA_REQ_PSSCR, paca_struct, requested_psscr); +#define STOP_SPR(x, f) OFFSET(x, paca_struct, stop_sprs.f) + STOP_SPR(STOP_PID, pid); + STOP_SPR(STOP_LDBAR, ldbar); + STOP_SPR(STOP_FSCR, fscr); + STOP_SPR(STOP_HFSCR, hfscr); + STOP_SPR(STOP_MMCR1, mmcr1); + STOP_SPR(STOP_MMCR2, mmcr2); + STOP_SPR(STOP_MMCRA, mmcra); #endif DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER); diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index 516ebef905c0..4621568277f2 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -85,7 +85,61 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300) std r3,_WORT(r1) mfspr r3,SPRN_WORC std r3,_WORC(r1) +/* + * On POWER9, there are idle states such as stop4, invoked via cpuidle, + * that lose hypervisor resources. In such cases, we need to save + * additional SPRs before entering those idle states so that they can + * be restored to their older values on wakeup from the idle state. + * + * On POWER8, the only such deep idle state is winkle which is used + * only in the context of CPU-Hotplug, where these additional SPRs are + * reinitiazed to a sane value. Hence there is no need to save/restore + * these SPRs. + */ +BEGIN_FTR_SECTION + blr +END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300) + +power9_save_additional_sprs: + mfspr r3, SPRN_PID + mfspr r4, SPRN_LDBAR + std r3, STOP_PID(r13) + std r4, STOP_LDBAR(r13) + mfspr r3, SPRN_FSCR + mfspr r4, SPRN_HFSCR + std r3, STOP_FSCR(r13) + std r4, STOP_HFSCR(r13) + + mfspr r3, SPRN_MMCRA + mfspr r4, SPRN_MMCR1 + std r3, STOP_MMCRA(r13) + std r4, STOP_MMCR1(r13) + + mfspr r3, SPRN_MMCR2 + std r3, STOP_MMCR2(r13) + blr + +power9_restore_additional_sprs: + ld r3,_LPCR(r1) + ld r4, STOP_PID(r13) + mtspr SPRN_LPCR,r3 + mtspr SPRN_PID, r4 + + ld r3, STOP_LDBAR(r13) + ld r4, STOP_FSCR(r13) + mtspr SPRN_LDBAR, r3 + mtspr SPRN_FSCR, r4 + + ld r3, STOP_HFSCR(r13) + ld r4, STOP_MMCRA(r13) + mtspr SPRN_HFSCR, r3 + mtspr SPRN_MMCRA, r4 + /* We have already restored PACA_MMCR0 */ + ld r3, STOP_MMCR1(r13) + ld r4, STOP_MMCR2(r13) + mtspr SPRN_MMCR1, r3 + mtspr SPRN_MMCR2, r4 blr /* @@ -803,9 +857,16 @@ no_segments: mtctr r12 bctrl +/* + * On POWER9, we can come here on wakeup from a cpuidle stop state. + * Hence restore the additional SPRs to the saved value. + * + * On POWER8, we come here only on winkle. Since winkle is used + * only in the case of CPU-Hotplug, we don't need to restore + * the additional SPRs. + */ BEGIN_FTR_SECTION - ld r4,_LPCR(r1) - mtspr SPRN_LPCR,r4 + bl power9_restore_additional_sprs END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) hypervisor_state_restored: -- 2.30.2