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From:   Pratik Rajesh Sampat <psampat@linux.ibm.com>
To:     linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
        mpe@ellerman.id.au, skiboot@lists.ozlabs.org, oohall@gmail.com,
        ego@linux.vnet.ibm.com, linuxram@us.ibm.com,
        pratik.r.sampat@gmail.com, psampat@linux.ibm.com
Subject: [PATCH v8 1/1] powerpc/powernv: Introduce support and parsing for self-save API
Date:   Thu, 23 Apr 2020 16:25:57 +0530
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This commit introduces and leverages the Self save API. The difference
between self-save and self-restore is that the value to be saved for the
SPR does not need to be passed to the call.

Add the new Self Save OPAL API call in the list of OPAL calls.

The device tree is parsed looking for the property "ibm,opal-self-save"
If self-save is supported then for all SPRs self-save is invoked for all
P9 supported registers. In the case self-save fails corresponding
self-restore call is invoked as a fallback.

Signed-off-by: Pratik Rajesh Sampat <psampat@linux.ibm.com>
---
 arch/powerpc/include/asm/opal-api.h        |  3 +-
 arch/powerpc/include/asm/opal.h            |  1 +
 arch/powerpc/platforms/powernv/idle.c      | 73 ++++++++++++++++++----
 arch/powerpc/platforms/powernv/opal-call.c |  1 +
 4 files changed, 64 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
index 1dffa3cb16ba..7ba698369083 100644
--- a/arch/powerpc/include/asm/opal-api.h
+++ b/arch/powerpc/include/asm/opal-api.h
@@ -214,7 +214,8 @@
 #define OPAL_SECVAR_GET				176
 #define OPAL_SECVAR_GET_NEXT			177
 #define OPAL_SECVAR_ENQUEUE_UPDATE		178
-#define OPAL_LAST				178
+#define OPAL_SLW_SELF_SAVE_REG			181
+#define OPAL_LAST				181
 
 #define QUIESCE_HOLD			1 /* Spin all calls at entry */
 #define QUIESCE_REJECT			2 /* Fail all calls with OPAL_BUSY */
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 9986ac34b8e2..a370b0e8d899 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -204,6 +204,7 @@ int64_t opal_handle_hmi2(__be64 *out_flags);
 int64_t opal_register_dump_region(uint32_t id, uint64_t start, uint64_t end);
 int64_t opal_unregister_dump_region(uint32_t id);
 int64_t opal_slw_set_reg(uint64_t cpu_pir, uint64_t sprn, uint64_t val);
+int64_t opal_slw_self_save_reg(uint64_t cpu_pir, uint64_t sprn);
 int64_t opal_config_cpu_idle_state(uint64_t state, uint64_t flag);
 int64_t opal_pci_set_phb_cxl_mode(uint64_t phb_id, uint64_t mode, uint64_t pe_number);
 int64_t opal_pci_get_pbcq_tunnel_bar(uint64_t phb_id, uint64_t *addr);
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 78599bca66c2..ada7ece24521 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -32,6 +32,11 @@
 #define P9_STOP_SPR_MSR 2000
 #define P9_STOP_SPR_PSSCR      855
 
+/* Caching the self-save functionality, lpcr, ptcr support */
+DEFINE_STATIC_KEY_FALSE(self_save_available);
+DEFINE_STATIC_KEY_FALSE(is_lpcr_self_save);
+DEFINE_STATIC_KEY_FALSE(is_ptcr_self_save);
+
 static u32 supported_cpuidle_states;
 struct pnv_idle_states_t *pnv_idle_states;
 int nr_pnv_idle_states;
@@ -61,6 +66,35 @@ static bool deepest_stop_found;
 
 static unsigned long power7_offline_type;
 
+/*
+ * Cache support for SPRs that support self-save as well as kernel save restore
+ * so that kernel does not duplicate efforts in saving and restoring SPRs
+ */
+static void cache_spr_self_save_support(u64 sprn)
+{
+	switch (sprn) {
+	case SPRN_LPCR:
+		static_branch_enable(&is_lpcr_self_save);
+		break;
+	case SPRN_PTCR:
+		static_branch_enable(&is_ptcr_self_save);
+		break;
+	}
+}
+
+static int pnv_save_one_spr(u64 pir, u64 sprn, u64 val)
+{
+	if (static_branch_likely(&self_save_available)) {
+		int rc = opal_slw_self_save_reg(pir, sprn);
+
+		if (!rc) {
+			cache_spr_self_save_support(sprn);
+			return rc;
+		}
+	}
+	return opal_slw_set_reg(pir, sprn, val);
+}
+
 static int pnv_save_sprs_for_deep_states(void)
 {
 	int cpu;
@@ -72,6 +106,7 @@ static int pnv_save_sprs_for_deep_states(void)
 	 * same across all cpus.
 	 */
 	uint64_t lpcr_val	= mfspr(SPRN_LPCR);
+	uint64_t ptcr_val	= mfspr(SPRN_PTCR);
 	uint64_t hid0_val	= mfspr(SPRN_HID0);
 	uint64_t hid1_val	= mfspr(SPRN_HID1);
 	uint64_t hid4_val	= mfspr(SPRN_HID4);
@@ -84,30 +119,34 @@ static int pnv_save_sprs_for_deep_states(void)
 		uint64_t pir = get_hard_smp_processor_id(cpu);
 		uint64_t hsprg0_val = (uint64_t)paca_ptrs[cpu];
 
-		rc = opal_slw_set_reg(pir, SPRN_HSPRG0, hsprg0_val);
+		rc = pnv_save_one_spr(pir, SPRN_HSPRG0, hsprg0_val);
 		if (rc != 0)
 			return rc;
 
-		rc = opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
+		rc = pnv_save_one_spr(pir, SPRN_LPCR, lpcr_val);
 		if (rc != 0)
 			return rc;
 
+		/*
+		 * No need to check for failure, if firmware fails to save then
+		 * kernel handles save-restore for PTCR
+		 */
+		pnv_save_one_spr(pir, SPRN_PTCR, ptcr_val);
+
 		if (cpu_has_feature(CPU_FTR_ARCH_300)) {
-			rc = opal_slw_set_reg(pir, P9_STOP_SPR_MSR, msr_val);
+			rc = pnv_save_one_spr(pir, P9_STOP_SPR_MSR, msr_val);
 			if (rc)
 				return rc;
 
-			rc = opal_slw_set_reg(pir,
+			rc = pnv_save_one_spr(pir,
 					      P9_STOP_SPR_PSSCR, psscr_val);
-
 			if (rc)
 				return rc;
 		}
 
 		/* HIDs are per core registers */
 		if (cpu_thread_in_core(cpu) == 0) {
-
-			rc = opal_slw_set_reg(pir, SPRN_HMEER, hmeer_val);
+			rc = pnv_save_one_spr(pir, SPRN_HMEER, hmeer_val);
 			if (rc != 0)
 				return rc;
 
@@ -658,7 +697,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 		mmcr0		= mfspr(SPRN_MMCR0);
 	}
 	if ((psscr & PSSCR_RL_MASK) >= pnv_first_spr_loss_level) {
-		sprs.lpcr	= mfspr(SPRN_LPCR);
+		if (!static_branch_unlikely(&is_lpcr_self_save))
+			sprs.lpcr	= mfspr(SPRN_LPCR);
 		sprs.hfscr	= mfspr(SPRN_HFSCR);
 		sprs.fscr	= mfspr(SPRN_FSCR);
 		sprs.pid	= mfspr(SPRN_PID);
@@ -672,7 +712,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 		sprs.mmcr1	= mfspr(SPRN_MMCR1);
 		sprs.mmcr2	= mfspr(SPRN_MMCR2);
 
-		sprs.ptcr	= mfspr(SPRN_PTCR);
+		if (!static_branch_unlikely(&is_ptcr_self_save))
+			sprs.ptcr	= mfspr(SPRN_PTCR);
 		sprs.rpr	= mfspr(SPRN_RPR);
 		sprs.tscr	= mfspr(SPRN_TSCR);
 		if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
@@ -756,7 +797,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 		goto core_woken;
 
 	/* Per-core SPRs */
-	mtspr(SPRN_PTCR,	sprs.ptcr);
+	if (!static_branch_unlikely(&is_ptcr_self_save))
+		mtspr(SPRN_PTCR,	sprs.ptcr);
 	mtspr(SPRN_RPR,		sprs.rpr);
 	mtspr(SPRN_TSCR,	sprs.tscr);
 
@@ -777,7 +819,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
 	atomic_unlock_and_stop_thread_idle();
 
 	/* Per-thread SPRs */
-	mtspr(SPRN_LPCR,	sprs.lpcr);
+	if (!static_branch_unlikely(&is_lpcr_self_save))
+		mtspr(SPRN_LPCR,	sprs.lpcr);
 	mtspr(SPRN_HFSCR,	sprs.hfscr);
 	mtspr(SPRN_FSCR,	sprs.fscr);
 	mtspr(SPRN_PID,		sprs.pid);
@@ -956,8 +999,10 @@ void pnv_program_cpu_hotplug_lpcr(unsigned int cpu, u64 lpcr_val)
 	 * Program the LPCR via stop-api only if the deepest stop state
 	 * can lose hypervisor context.
 	 */
-	if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
-		opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
+	if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT) {
+		if (!static_branch_unlikely(&is_lpcr_self_save))
+			opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
+	}
 }
 
 /*
@@ -1298,6 +1343,8 @@ static int pnv_parse_cpuidle_dt(void)
 		}
 		for (i = 0; i < nr_idle_states; i++)
 			pnv_idle_states[i].psscr_mask = temp_u64[i];
+		if (of_property_read_bool(np, "ibm,opal-self-save"))
+			static_branch_enable(&self_save_available);
 	}
 
 	/*
diff --git a/arch/powerpc/platforms/powernv/opal-call.c b/arch/powerpc/platforms/powernv/opal-call.c
index 5cd0f52d258f..11e0ceb90de0 100644
--- a/arch/powerpc/platforms/powernv/opal-call.c
+++ b/arch/powerpc/platforms/powernv/opal-call.c
@@ -223,6 +223,7 @@ OPAL_CALL(opal_handle_hmi,			OPAL_HANDLE_HMI);
 OPAL_CALL(opal_handle_hmi2,			OPAL_HANDLE_HMI2);
 OPAL_CALL(opal_config_cpu_idle_state,		OPAL_CONFIG_CPU_IDLE_STATE);
 OPAL_CALL(opal_slw_set_reg,			OPAL_SLW_SET_REG);
+OPAL_CALL(opal_slw_self_save_reg,		OPAL_SLW_SELF_SAVE_REG);
 OPAL_CALL(opal_register_dump_region,		OPAL_REGISTER_DUMP_REGION);
 OPAL_CALL(opal_unregister_dump_region,		OPAL_UNREGISTER_DUMP_REGION);
 OPAL_CALL(opal_pci_set_phb_cxl_mode,		OPAL_PCI_SET_PHB_CAPI_MODE);
-- 
2.17.1