intel_idle: Allow ACPI _CST to be used for selected known processors

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>

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 28812d9..a072b84 100644 (file)
--- 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;
@@ -91,6 +92,11 @@ static void intel_idle_s2idle(struct cpuidle_device *dev,
 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.
  * If this flag is set, SW flushes the TLB, so even if the
@@ -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) {