HID: multitouch: optimize the sticky fingers timer

Instead of unconditionally expiring the timer and calling a long
mt_release_contacts(), we can check if some slots are used when the
timer expires.

We can also remove the timer if we happen to receive all the releases.

The logic behind the MT_IO_FLAGS_PENDING_SLOTS could be implemented by
counting how many slots are active, but using bits feels slightly more
efficient.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: Arek Burdach <arek.burdach@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 25641b2f90abb2f3f3411c397146b8f8988f2b05..f3e35e7a189d30aba1b6619ddba328cbec75a836 100644 (file)
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -79,6 +79,8 @@ MODULE_LICENSE("GPL");
 #define MT_BUTTONTYPE_CLICKPAD         0
 
 #define MT_IO_FLAGS_RUNNING            0
+#define MT_IO_FLAGS_ACTIVE_SLOTS       1
+#define MT_IO_FLAGS_PENDING_SLOTS      2
 
 struct mt_slot {
        __s32 x, y, cx, cy, p, w, h;
@@ -705,6 +707,8 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
                        input_event(input, EV_ABS, ABS_MT_PRESSURE, s->p);
                        input_event(input, EV_ABS, ABS_MT_TOUCH_MAJOR, major);
                        input_event(input, EV_ABS, ABS_MT_TOUCH_MINOR, minor);
+
+                       set_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags);
                }
        }
 
@@ -720,6 +724,11 @@ static void mt_sync_frame(struct mt_device *td, struct input_dev *input)
        input_mt_sync_frame(input);
        input_sync(input);
        td->num_received = 0;
+       if (test_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags))
+               set_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags);
+       else
+               clear_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags);
+       clear_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags);
 }
 
 static int mt_touch_event(struct hid_device *hid, struct hid_field *field,
@@ -859,8 +868,13 @@ static void mt_touch_report(struct hid_device *hid, struct hid_report *report)
         * only affect laggish machines and the ones that have a firmware
         * defect.
         */
-       if (td->mtclass.quirks & MT_QUIRK_STICKY_FINGERS)
-               mod_timer(&td->release_timer, jiffies + msecs_to_jiffies(100));
+       if (td->mtclass.quirks & MT_QUIRK_STICKY_FINGERS) {
+               if (test_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags))
+                       mod_timer(&td->release_timer,
+                                 jiffies + msecs_to_jiffies(100));
+               else
+                       del_timer(&td->release_timer);
+       }
 
        clear_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
 }
@@ -1210,7 +1224,8 @@ static void mt_expired_timeout(unsigned long arg)
         */
        if (test_and_set_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
                return;
-       mt_release_contacts(hdev);
+       if (test_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags))
+               mt_release_contacts(hdev);
        clear_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
 }