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Subject[PATCH v1 08/10] intel_idle: Allow ACPI _CST to be used for selected known processors
Date
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Update the intel_idle driver to get the C-states information from ACPI
_CST in some cases in which the processor is known to the driver, as long as
that information is available and the new use_acpi flag is set in the
profile of the processor in question.

In the cases when there is a specific table of C-states for the given
processor in the driver, that table is used as the primary source of
information on the available C-states, but if ACPI _CST is present,
the C-states that are not listed by it will not be enabled by default
(they still can be enabled later by user space via sysfs, though).

The new CPUIDLE_FLAG_ALWAYS_ENABLE flag can be used for marking
C-states that should be enabled by default even if they are not
listed by ACPI _CST.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Changes from the RFC version:
- Subject and changelog update.
- Call the new state flag CPUIDLE_FLAG_ALWAYS_ENABLE (instead of _IGNORE_ACPI).

---
drivers/idle/intel_idle.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 28812d93d59a..a072b84d9595 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -80,6 +80,7 @@ struct idle_cpu {
unsigned long auto_demotion_disable_flags;
bool byt_auto_demotion_disable_flag;
bool disable_promotion_to_c1e;
+ bool use_acpi;
};

static const struct idle_cpu *icpu;
@@ -90,6 +91,11 @@ static void intel_idle_s2idle(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index);
static struct cpuidle_state *cpuidle_state_table;

+/*
+ * Enable this state by default even if the ACPI _CST does not list it.
+ */
+#define CPUIDLE_FLAG_ALWAYS_ENABLE BIT(15)
+
/*
* Set this flag for states where the HW flushes the TLB for us
* and so we don't need cross-calls to keep it consistent.
@@ -1230,9 +1236,33 @@ static void intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
state->enter_s2idle = intel_idle_s2idle;
}
}
+
+static bool intel_idle_off_by_default(u32 mwait_hint)
+{
+ int cstate, limit;
+
+ /*
+ * If there are no _CST C-states, do not disable any C-states by
+ * default.
+ */
+ if (!acpi_state_table.count)
+ return false;
+
+ limit = min_t(int, CPUIDLE_STATE_MAX, acpi_state_table.count);
+ /*
+ * If limit > 0, intel_idle_cst_usable() has returned 'true', so all of
+ * the interesting states are ACPI_CSTATE_FFH.
+ */
+ for (cstate = 1; cstate < limit; cstate++) {
+ if (acpi_state_table.states[cstate].address == mwait_hint)
+ return false;
+ }
+ return true;
+}
#else /* !CONFIG_ACPI_PROCESSOR_CSTATE */
static inline bool intel_idle_acpi_cst_extract(void) { return false; }
static inline void intel_idle_init_cstates_acpi(struct cpuidle_driver *drv) { }
+static inline bool intel_idle_off_by_default(u32 mwait_hint) { return false; }
#endif /* !CONFIG_ACPI_PROCESSOR_CSTATE */

/*
@@ -1273,10 +1303,13 @@ static int __init intel_idle_probe(void)
pr_debug("MWAIT substates: 0x%x\n", mwait_substates);

icpu = (const struct idle_cpu *)id->driver_data;
- if (icpu)
+ if (icpu) {
cpuidle_state_table = icpu->state_table;
- else if (!intel_idle_acpi_cst_extract())
+ if (icpu->use_acpi)
+ intel_idle_acpi_cst_extract();
+ } else if (!intel_idle_acpi_cst_extract()) {
return -ENODEV;
+ }

pr_debug("v" INTEL_IDLE_VERSION " model 0x%X\n",
boot_cpu_data.x86_model);
@@ -1484,7 +1517,13 @@ static void intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
continue;

/* Structure copy. */
- drv->states[drv->state_count++] = cpuidle_state_table[cstate];
+ drv->states[drv->state_count] = cpuidle_state_table[cstate];
+
+ if (icpu->use_acpi && intel_idle_off_by_default(mwait_hint) &&
+ !(cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_ALWAYS_ENABLE))
+ drv->states[drv->state_count].flags |= CPUIDLE_FLAG_OFF;
+
+ drv->state_count++;
}

if (icpu->byt_auto_demotion_disable_flag) {
--
2.16.4




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