ACPI: Enforce T-state limit changes immediately

When a T-state limit change notification is received,
Linux must evaluate _TPC and change its current
T-state immediately to comply with the new limit.

Previously, Linux would notice the new limit
only upon the next throttling change.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 49 insertions, 1 deletions

diff --git a/drivers/acpi/processor_throttling.c b/drivers/acpi/processor_throttling.c
index 0b8204e7082a..5fa8ac1c0c84 100644
--- a/drivers/acpi/processor_throttling.c
+++ b/drivers/acpi/processor_throttling.c
@@ -70,7 +70,55 @@ static int acpi_processor_get_platform_limit(struct acpi_processor *pr)
 
 int acpi_processor_tstate_has_changed(struct acpi_processor *pr)
 {
-        return acpi_processor_get_platform_limit(pr);
+        int result = 0;
+        int throttling_limit;
+        int current_state;
+        struct acpi_processor_limit *limit;
+        int target_state;
+
+        result = acpi_processor_get_platform_limit(pr);
+        if (result) {
+                /* Throttling Limit is unsupported */
+                return result;
+        }
+
+        throttling_limit = pr->throttling_platform_limit;
+        if (throttling_limit >= pr->throttling.state_count) {
+                /* Uncorrect Throttling Limit */
+                return -EINVAL;
+        }
+
+        current_state = pr->throttling.state;
+        if (current_state > throttling_limit) {
+                /*
+                 * The current state can meet the requirement of
+                 * _TPC limit. But it is reasonable that OSPM changes
+                 * t-states from high to low for better performance.
+                 * Of course the limit condition of thermal
+                 * and user should be considered.
+                 */
+                limit = &pr->limit;
+                target_state = throttling_limit;
+                if (limit->thermal.tx > target_state)
+                        target_state = limit->thermal.tx;
+                if (limit->user.tx > target_state)
+                        target_state = limit->user.tx;
+        } else if (current_state == throttling_limit) {
+                /*
+                 * Unnecessary to change the throttling state
+                 */
+                return 0;
+        } else {
+                /*
+                 * If the current state is lower than the limit of _TPC, it
+                 * will be forced to switch to the throttling state defined
+                 * by throttling_platfor_limit.
+                 * Because the previous state meets with the limit condition
+                 * of thermal and user, it is unnecessary to check it again.
+                 */
+                target_state = throttling_limit;
+        }
+        return acpi_processor_set_throttling(pr, target_state);
 }
 
 /*