powerpc/powernv: Add platform support for stop instruction

POWER ISA v3 defines a new idle processor core mechanism. In summary,
 a) new instruction named stop is added. This instruction replaces
	instructions like nap, sleep, rvwinkle.
 b) new per thread SPR named Processor Stop Status and Control Register
	(PSSCR) is added which controls the behavior of stop instruction.

PSSCR layout:
----------------------------------------------------------
| PLS | /// | SD | ESL | EC | PSLL | /// | TR | MTL | RL |
----------------------------------------------------------
0      4     41   42    43   44     48    54   56    60

PSSCR key fields:
	Bits 0:3  - Power-Saving Level Status. This field indicates the lowest
	power-saving state the thread entered since stop instruction was last
	executed.

	Bit 42 - Enable State Loss
	0 - No state is lost irrespective of other fields
	1 - Allows state loss

	Bits 44:47 - Power-Saving Level Limit
	This limits the power-saving level that can be entered into.

	Bits 60:63 - Requested Level
	Used to specify which power-saving level must be entered on executing
	stop instruction

This patch adds support for stop instruction and PSSCR handling.

Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 145 insertions, 29 deletions

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 8a77f5c4159e..8219e22c2b91 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -27,9 +27,12 @@
 #include "powernv.h"
 #include "subcore.h"
 
+/* Power ISA 3.0 allows for stop states 0x0 - 0xF */
+#define MAX_STOP_STATE	0xF
+
 static u32 supported_cpuidle_states;
 
-static int pnv_save_sprs_for_winkle(void)
+static int pnv_save_sprs_for_deep_states(void)
 {
 	int cpu;
 	int rc;
@@ -50,15 +53,19 @@ static int pnv_save_sprs_for_winkle(void)
 		uint64_t pir = get_hard_smp_processor_id(cpu);
 		uint64_t hsprg0_val = (uint64_t)&paca[cpu];
 
-		/*
-		 * HSPRG0 is used to store the cpu's pointer to paca. Hence last
-		 * 3 bits are guaranteed to be 0. Program slw to restore HSPRG0
-		 * with 63rd bit set, so that when a thread wakes up at 0x100 we
-		 * can use this bit to distinguish between fastsleep and
-		 * deep winkle.
-		 */
-		hsprg0_val |= 1;
-
+		if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
+			/*
+			 * HSPRG0 is used to store the cpu's pointer to paca.
+			 * Hence last 3 bits are guaranteed to be 0. Program
+			 * slw to restore HSPRG0 with 63rd bit set, so that
+			 * when a thread wakes up at 0x100 we can use this bit
+			 * to distinguish between fastsleep and deep winkle.
+			 * This is not necessary with stop/psscr since PLS
+			 * field of psscr indicates which state we are waking
+			 * up from.
+			 */
+			hsprg0_val |= 1;
+		}
 		rc = opal_slw_set_reg(pir, SPRN_HSPRG0, hsprg0_val);
 		if (rc != 0)
 			return rc;
@@ -130,8 +137,8 @@ static void pnv_alloc_idle_core_states(void)
 
 	update_subcore_sibling_mask();
 
-	if (supported_cpuidle_states & OPAL_PM_WINKLE_ENABLED)
-		pnv_save_sprs_for_winkle();
+	if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
+		pnv_save_sprs_for_deep_states();
 }
 
 u32 pnv_get_supported_cpuidle_states(void)
@@ -230,43 +237,151 @@ static DEVICE_ATTR(fastsleep_workaround_applyonce, 0600,
 			show_fastsleep_workaround_applyonce,
 			store_fastsleep_workaround_applyonce);
 
-static int __init pnv_init_idle_states(void)
+
+/*
+ * Used for ppc_md.power_save which needs a function with no parameters
+ */
+static void power9_idle(void)
 {
-	struct device_node *power_mgt;
-	int dt_idle_states;
-	u32 *flags;
-	int i;
+	/* Requesting stop state 0 */
+	power9_idle_stop(0);
+}
+/*
+ * First deep stop state. Used to figure out when to save/restore
+ * hypervisor context.
+ */
+u64 pnv_first_deep_stop_state = MAX_STOP_STATE;
 
-	supported_cpuidle_states = 0;
+/*
+ * Power ISA 3.0 idle initialization.
+ *
+ * POWER ISA 3.0 defines a new SPR Processor stop Status and Control
+ * Register (PSSCR) to control idle behavior.
+ *
+ * PSSCR layout:
+ * ----------------------------------------------------------
+ * | PLS | /// | SD | ESL | EC | PSLL | /// | TR | MTL | RL |
+ * ----------------------------------------------------------
+ * 0      4     41   42    43   44     48    54   56    60
+ *
+ * PSSCR key fields:
+ *	Bits 0:3  - Power-Saving Level Status (PLS). This field indicates the
+ *	lowest power-saving state the thread entered since stop instruction was
+ *	last executed.
+ *
+ *	Bit 41 - Status Disable(SD)
+ *	0 - Shows PLS entries
+ *	1 - PLS entries are all 0
+ *
+ *	Bit 42 - Enable State Loss
+ *	0 - No state is lost irrespective of other fields
+ *	1 - Allows state loss
+ *
+ *	Bit 43 - Exit Criterion
+ *	0 - Exit from power-save mode on any interrupt
+ *	1 - Exit from power-save mode controlled by LPCR's PECE bits
+ *
+ *	Bits 44:47 - Power-Saving Level Limit
+ *	This limits the power-saving level that can be entered into.
+ *
+ *	Bits 60:63 - Requested Level
+ *	Used to specify which power-saving level must be entered on executing
+ *	stop instruction
+ *
+ * @np: /ibm,opal/power-mgt device node
+ * @flags: cpu-idle-state-flags array
+ * @dt_idle_states: Number of idle state entries
+ * Returns 0 on success
+ */
+static int __init pnv_arch300_idle_init(struct device_node *np, u32 *flags,
+					int dt_idle_states)
+{
+	u64 *psscr_val = NULL;
+	int rc = 0, i;
 
-	if (cpuidle_disable != IDLE_NO_OVERRIDE)
+	psscr_val = kcalloc(dt_idle_states, sizeof(*psscr_val),
+				GFP_KERNEL);
+	if (!psscr_val) {
+		rc = -1;
 		goto out;
-
-	if (!firmware_has_feature(FW_FEATURE_OPAL))
+	}
+	if (of_property_read_u64_array(np,
+		"ibm,cpu-idle-state-psscr",
+		psscr_val, dt_idle_states)) {
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-states-psscr in DT\n");
+		rc = -1;
 		goto out;
+	}
 
-	power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
-	if (!power_mgt) {
+	/*
+	 * Set pnv_first_deep_stop_state to the first stop level
+	 * to cause hypervisor state loss
+	 */
+	pnv_first_deep_stop_state = MAX_STOP_STATE;
+	for (i = 0; i < dt_idle_states; i++) {
+		u64 psscr_rl = psscr_val[i] & PSSCR_RL_MASK;
+
+		if ((flags[i] & OPAL_PM_LOSE_FULL_CONTEXT) &&
+		     (pnv_first_deep_stop_state > psscr_rl))
+			pnv_first_deep_stop_state = psscr_rl;
+	}
+
+out:
+	kfree(psscr_val);
+	return rc;
+}
+
+/*
+ * Probe device tree for supported idle states
+ */
+static void __init pnv_probe_idle_states(void)
+{
+	struct device_node *np;
+	int dt_idle_states;
+	u32 *flags = NULL;
+	int i;
+
+	np = of_find_node_by_path("/ibm,opal/power-mgt");
+	if (!np) {
 		pr_warn("opal: PowerMgmt Node not found\n");
 		goto out;
 	}
-	dt_idle_states = of_property_count_u32_elems(power_mgt,
+	dt_idle_states = of_property_count_u32_elems(np,
 			"ibm,cpu-idle-state-flags");
 	if (dt_idle_states < 0) {
 		pr_warn("cpuidle-powernv: no idle states found in the DT\n");
 		goto out;
 	}
 
-	flags = kzalloc(sizeof(*flags) * dt_idle_states, GFP_KERNEL);
-	if (of_property_read_u32_array(power_mgt,
+	flags = kcalloc(dt_idle_states, sizeof(*flags),  GFP_KERNEL);
+
+	if (of_property_read_u32_array(np,
 			"ibm,cpu-idle-state-flags", flags, dt_idle_states)) {
 		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-flags in DT\n");
-		goto out_free;
+		goto out;
+	}
+
+	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+		if (pnv_arch300_idle_init(np, flags, dt_idle_states))
+			goto out;
 	}
 
 	for (i = 0; i < dt_idle_states; i++)
 		supported_cpuidle_states |= flags[i];
 
+out:
+	kfree(flags);
+}
+static int __init pnv_init_idle_states(void)
+{
+
+	supported_cpuidle_states = 0;
+
+	if (cpuidle_disable != IDLE_NO_OVERRIDE)
+		goto out;
+
+	pnv_probe_idle_states();
+
 	if (!(supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
 		patch_instruction(
 			(unsigned int *)pnv_fastsleep_workaround_at_entry,
@@ -288,8 +403,9 @@ static int __init pnv_init_idle_states(void)
 
 	if (supported_cpuidle_states & OPAL_PM_NAP_ENABLED)
 		ppc_md.power_save = power7_idle;
-out_free:
-	kfree(flags);
+	else if (supported_cpuidle_states & OPAL_PM_STOP_INST_FAST)
+		ppc_md.power_save = power9_idle;
+
 out:
 	return 0;
 }