[Skiboot] [PATCH v4 6/8] slw: Limit fused cores P9 to STOP0/1/2

[Vaidyanathan Srinivasan]

From: Benjamin Herrenschmidt <benh at kernel.crashing.org>

Linux doesn't know how to properly restore state on "both halves" of
a fused core, so limit ourselves to STOP states that don't require
HV state restore for bare metal kernels (KVM is still broken) until
we add a new representation for STOP states.

The new representation will have per-state versioning so that we
can control their individual enablement based on whether the OS
has the necessary workarounds to make them work.

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Signed-off-by: Michael Neuling <mikey at neuling.org>
Signed-off-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
---
 hw/slw.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/hw/slw.c b/hw/slw.c
index 2f761979..f49b38ed 100644
--- a/hw/slw.c
+++ b/hw/slw.c
@@ -688,6 +688,83 @@ static struct cpu_idle_states power9_mambo_cpu_idle_states[] = {
 
 };
 
+/*
+ * cpu_idle_states for fused core configuration
+ * These will be a subset of power9 idle states.
+ */
+static struct cpu_idle_states power9_fusedcore_cpu_idle_states[] = {
+	{
+		.name = "stop0_lite", /* Enter stop0 with no state loss */
+		.latency_ns = 1000,
+		.residency_ns = 10000,
+		.flags = 0*OPAL_PM_DEC_STOP \
+		       | 0*OPAL_PM_TIMEBASE_STOP  \
+		       | 0*OPAL_PM_LOSE_USER_CONTEXT \
+		       | 0*OPAL_PM_LOSE_HYP_CONTEXT \
+		       | 0*OPAL_PM_LOSE_FULL_CONTEXT \
+		       | 1*OPAL_PM_STOP_INST_FAST,
+		.pm_ctrl_reg_val = OPAL_PM_PSSCR_RL(0) \
+				 | OPAL_PM_PSSCR_MTL(3) \
+				 | OPAL_PM_PSSCR_TR(3),
+		.pm_ctrl_reg_mask = OPAL_PM_PSSCR_MASK },
+	{
+		.name = "stop0",
+		.latency_ns = 2000,
+		.residency_ns = 20000,
+		.flags = 0*OPAL_PM_DEC_STOP \
+		       | 0*OPAL_PM_TIMEBASE_STOP  \
+		       | 1*OPAL_PM_LOSE_USER_CONTEXT \
+		       | 0*OPAL_PM_LOSE_HYP_CONTEXT \
+		       | 0*OPAL_PM_LOSE_FULL_CONTEXT \
+		       | 1*OPAL_PM_STOP_INST_FAST,
+		.pm_ctrl_reg_val = OPAL_PM_PSSCR_RL(0) \
+				 | OPAL_PM_PSSCR_MTL(3) \
+				 | OPAL_PM_PSSCR_TR(3) \
+				 | OPAL_PM_PSSCR_ESL \
+				 | OPAL_PM_PSSCR_EC,
+		.pm_ctrl_reg_mask = OPAL_PM_PSSCR_MASK },
+
+	/* stop1_lite has been removed since it adds no additional benefit over stop0_lite */
+
+	{
+		.name = "stop1",
+		.latency_ns = 5000,
+		.residency_ns = 50000,
+		.flags = 0*OPAL_PM_DEC_STOP \
+		       | 0*OPAL_PM_TIMEBASE_STOP  \
+		       | 1*OPAL_PM_LOSE_USER_CONTEXT \
+		       | 0*OPAL_PM_LOSE_HYP_CONTEXT \
+		       | 0*OPAL_PM_LOSE_FULL_CONTEXT \
+		       | 1*OPAL_PM_STOP_INST_FAST,
+		.pm_ctrl_reg_val = OPAL_PM_PSSCR_RL(1) \
+				 | OPAL_PM_PSSCR_MTL(3) \
+				 | OPAL_PM_PSSCR_TR(3) \
+				 | OPAL_PM_PSSCR_ESL \
+				 | OPAL_PM_PSSCR_EC,
+		.pm_ctrl_reg_mask = OPAL_PM_PSSCR_MASK },
+	/*
+	 * stop2_lite has been removed since currently it adds minimal benefit over stop2.
+	 * However, the benefit is eclipsed by the time required to ungate the clocks
+	 */
+
+	{
+		.name = "stop2",
+		.latency_ns = 10000,
+		.residency_ns = 100000,
+		.flags = 0*OPAL_PM_DEC_STOP \
+		       | 0*OPAL_PM_TIMEBASE_STOP  \
+		       | 1*OPAL_PM_LOSE_USER_CONTEXT \
+		       | 0*OPAL_PM_LOSE_HYP_CONTEXT \
+		       | 0*OPAL_PM_LOSE_FULL_CONTEXT \
+		       | 1*OPAL_PM_STOP_INST_FAST,
+		.pm_ctrl_reg_val = OPAL_PM_PSSCR_RL(2) \
+				 | OPAL_PM_PSSCR_MTL(3) \
+				 | OPAL_PM_PSSCR_TR(3) \
+				 | OPAL_PM_PSSCR_ESL \
+				 | OPAL_PM_PSSCR_EC,
+		.pm_ctrl_reg_mask = OPAL_PM_PSSCR_MASK },
+};
+
 static void slw_late_init_p9(struct proc_chip *chip)
 {
 	struct cpu_thread *c;
@@ -772,6 +849,9 @@ void add_cpu_idle_state_properties(void)
 		if (proc_chip_quirks & QUIRK_MAMBO_CALLOUTS) {
 			states = power9_mambo_cpu_idle_states;
 			nr_states = ARRAY_SIZE(power9_mambo_cpu_idle_states);
+		} else if (this_cpu()->is_fused_core) {
+			states = power9_fusedcore_cpu_idle_states;
+			nr_states = ARRAY_SIZE(power9_fusedcore_cpu_idle_states);
 		} else {
 			states = power9_cpu_idle_states;
 			nr_states = ARRAY_SIZE(power9_cpu_idle_states);
-- 
2.24.1