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Subject[v2 PATCH] powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT states when stop-api fails
Date
From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Currently, we use the opal call opal_slw_set_reg() to inform the
Sleep-Winkle Engine (SLW) to restore the contents of some of the
Hypervisor state on wakeup from deep idle states that lose full
hypervisor context (characterized by the flag
OPAL_PM_LOSE_FULL_CONTEXT).

However, the current code has a bug in that if opal_slw_set_reg()
fails, we don't disable the use of these deep states (winkle on
POWER8, stop4 onwards on POWER9).

This patch fixes this bug by ensuring that if programing the
sleep-winkle engine to restore the hypervisor states in
pnv_save_sprs_for_deep_states() fails, then we exclude such states by
clearing the OPAL_PM_LOSE_FULL_CONTEXT flag from
supported_cpuidle_states. As a result POWER8 will be prevented from
using winkle for CPU-Hotplug, and POWER9 will put the offlined CPUs to
the default stop state when available.

Further, we ensure in the initialization of the cpuidle-powernv driver
to only include those states whose flags are present in
supported_cpuidle_states, thereby skipping OPAL_PM_LOSE_FULL_CONTEXT
states when they have been disabled due to stop-api failure.

Fixes: 1e1601b38e6 ("powerpc/powernv/idle: Restore SPRs for deep idle
states via stop API.")

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
---
v2 --> v1:
Do the bare minimum required to exclude the LOSE_FULL_CONTEXT
states.

arch/powerpc/platforms/powernv/idle.c | 41 ++++++++++++++++++++++++++++++++---
drivers/cpuidle/cpuidle-powernv.c | 10 +++++++++
2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 2abee07..a553aee 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -56,6 +56,7 @@
*/
static u64 pnv_deepest_stop_psscr_val;
static u64 pnv_deepest_stop_psscr_mask;
+static u64 pnv_deepest_stop_flag;
static bool deepest_stop_found;

static int pnv_save_sprs_for_deep_states(void)
@@ -185,8 +186,40 @@ static void pnv_alloc_idle_core_states(void)

update_subcore_sibling_mask();

- if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT)
- pnv_save_sprs_for_deep_states();
+ if (supported_cpuidle_states & OPAL_PM_LOSE_FULL_CONTEXT) {
+ int rc = pnv_save_sprs_for_deep_states();
+
+ if (likely(!rc))
+ return;
+
+ /*
+ * The stop-api is unable to restore hypervisor
+ * resources on wakeup from platform idle states which
+ * lose full context. So disable such states.
+ */
+ supported_cpuidle_states &= ~OPAL_PM_LOSE_FULL_CONTEXT;
+ pr_warn("cpuidle-powernv: Disabling idle states that lose full context\n");
+ pr_warn("cpuidle-powernv: Idle power-savings, CPU-Hotplug affected\n");
+
+ if (cpu_has_feature(CPU_FTR_ARCH_300) &&
+ (pnv_deepest_stop_flag & OPAL_PM_LOSE_FULL_CONTEXT)) {
+ /*
+ * Use the default stop state for CPU-Hotplug
+ * if available.
+ */
+ if (default_stop_found) {
+ pnv_deepest_stop_psscr_val =
+ pnv_default_stop_val;
+ pnv_deepest_stop_psscr_mask =
+ pnv_default_stop_mask;
+ pr_warn("cpuidle-powernv: Offlined CPUs will stop with psscr = 0x%016llx\n",
+ pnv_deepest_stop_psscr_val);
+ } else { /* Fallback to snooze loop for CPU-Hotplug */
+ deepest_stop_found = false;
+ pr_warn("cpuidle-powernv: Offlined CPUs will busy wait\n");
+ }
+ }
+ }
}

u32 pnv_get_supported_cpuidle_states(void)
@@ -375,7 +408,8 @@ unsigned long pnv_cpu_offline(unsigned int cpu)
pnv_deepest_stop_psscr_val;
srr1 = power9_idle_stop(psscr);

- } else if (idle_states & OPAL_PM_WINKLE_ENABLED) {
+ } else if ((idle_states & OPAL_PM_WINKLE_ENABLED) &&
+ (idle_states & OPAL_PM_LOSE_FULL_CONTEXT)) {
srr1 = power7_idle_insn(PNV_THREAD_WINKLE);
} else if ((idle_states & OPAL_PM_SLEEP_ENABLED) ||
(idle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
@@ -553,6 +587,7 @@ static int __init pnv_power9_idle_init(struct device_node *np, u32 *flags,
max_residency_ns = residency_ns[i];
pnv_deepest_stop_psscr_val = psscr_val[i];
pnv_deepest_stop_psscr_mask = psscr_mask[i];
+ pnv_deepest_stop_flag = flags[i];
deepest_stop_found = true;
}

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 37b0698..42896a6 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -235,6 +235,7 @@ static inline int validate_dt_prop_sizes(const char *prop1, int prop1_len,
return -1;
}

+extern u32 pnv_get_supported_cpuidle_states(void);
static int powernv_add_idle_states(void)
{
struct device_node *power_mgt;
@@ -248,6 +249,8 @@ static int powernv_add_idle_states(void)
const char *names[CPUIDLE_STATE_MAX];
u32 has_stop_states = 0;
int i, rc;
+ u32 supported_flags = pnv_get_supported_cpuidle_states();
+

/* Currently we have snooze statically defined */

@@ -362,6 +365,13 @@ static int powernv_add_idle_states(void)
for (i = 0; i < dt_idle_states; i++) {
unsigned int exit_latency, target_residency;
bool stops_timebase = false;
+
+ /*
+ * Skip the platform idle state whose flag isn't in
+ * the supported_cpuidle_states flag mask.
+ */
+ if ((flags[i] & supported_flags) != flags[i])
+ continue;
/*
* If an idle state has exit latency beyond
* POWERNV_THRESHOLD_LATENCY_NS then don't use it
--
1.9.4
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