powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT states when stop-api fails

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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 2abee070373fb3a8b757b8d3cb269e5d0b89dff6..a553aeea7af683812ba2f5a80d65e97cda163919 100644 (file)
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -56,6 +56,7 @@ u64 pnv_first_deep_stop_state = MAX_STOP_STATE;
  */
 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 37b0698b7193e60be4107a8be107285e55c65877..42896a67aeae38325cbda2acb7ca655c1b43915c 100644 (file)
--- 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