[PATCH v13 13/15] HID: nintendo: prevent needless queueing of the rumble worker

["Daniel J. Ogorchock" <djogorchock@gmail.com>]

This patch adds a check for if the rumble queue ringbuffer is empty
prior to queuing the rumble workqueue. If the current rumble setting is
using a non-zero amplitude though, it will queue the worker anyway. This
is because the controller will automatically disable the rumble effect
if it isn't "refreshed".

This change improves bluetooth communication reliability with the
controller, since it reduces the amount of traffic.

Signed-off-by: Daniel J. Ogorchock <djogorchock@gmail.com>
---
 drivers/hid/hid-nintendo.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-nintendo.c b/drivers/hid/hid-nintendo.c
index cdb931d9bfae4..7e9b7ebc5a674 100644
--- a/drivers/hid/hid-nintendo.c
+++ b/drivers/hid/hid-nintendo.c
@@ -378,6 +378,7 @@ struct joycon_ctlr {
 	u16 rumble_lh_freq;
 	u16 rumble_rl_freq;
 	u16 rumble_rh_freq;
+	bool rumble_zero_amp;
 };
 
 /* Helper macros for checking controller type */
@@ -777,7 +778,9 @@ static void joycon_parse_report(struct joycon_ctlr *ctlr,
 
 	spin_lock_irqsave(&ctlr->lock, flags);
 	if (IS_ENABLED(CONFIG_NINTENDO_FF) && rep->vibrator_report &&
-	    (msecs - ctlr->rumble_msecs) >= JC_RUMBLE_PERIOD_MS)
+	    (msecs - ctlr->rumble_msecs) >= JC_RUMBLE_PERIOD_MS &&
+	    (ctlr->rumble_queue_head != ctlr->rumble_queue_tail ||
+	     !ctlr->rumble_zero_amp))
 		queue_work(ctlr->rumble_queue, &ctlr->rumble_worker);
 
 	/* Parse the battery status */
@@ -1036,6 +1039,8 @@ static int joycon_set_rumble(struct joycon_ctlr *ctlr, u16 amp_r, u16 amp_l,
 	freq_r_high = ctlr->rumble_rh_freq;
 	freq_l_low = ctlr->rumble_ll_freq;
 	freq_l_high = ctlr->rumble_lh_freq;
+	/* this flag is used to reduce subcommand traffic */
+	ctlr->rumble_zero_amp = (amp_l == 0) && (amp_r == 0);
 	spin_unlock_irqrestore(&ctlr->lock, flags);
 
 	/* right joy-con */
-- 
2.31.1