HID: nintendo: fix rumble rate limiter

It's been discovered that BT controller disconnect events correlate to
erratic input report timestamp deltas.

In experimentation, it's been found that ensuring that multiple
timestamp deltas are consistent prior to transmitting a rumble packet
drastically reduces the occurence rate of BT disconnects.

Alter the joycon_enforce_subcmd_rate() function to use this new
approach.

Signed-off-by: Daniel J. Ogorchock <djogorchock@gmail.com>
Reviewed-by: Silvan Jegen <s.jegen@gmail.com
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Alexandre Frade <kernel@xanmod.org>

drivers/hid/hid-nintendo.c

@@ -433,7 +433,9 @@ struct joycon_ctlr {
 	u8 usb_ack_match;
 	u8 subcmd_ack_match;
 	bool received_input_report;
+	unsigned int last_input_report_msecs;
 	unsigned int last_subcmd_sent_msecs;
+	unsigned int consecutive_valid_report_deltas;
 
 	/* factory calibration data */
 	struct joycon_stick_cal left_stick_cal_x;
@@ -543,19 +545,54 @@ static void joycon_wait_for_input_report(struct joycon_ctlr *ctlr)
  * Sending subcommands and/or rumble data at too high a rate can cause bluetooth
  * controller disconnections.
  */
+#define JC_INPUT_REPORT_MIN_DELTA	8
+#define JC_INPUT_REPORT_MAX_DELTA	17
+#define JC_SUBCMD_TX_OFFSET_MS		4
+#define JC_SUBCMD_VALID_DELTA_REQ	3
+#define JC_SUBCMD_RATE_MAX_ATTEMPTS	500
+#define JC_SUBCMD_RATE_LIMITER_USB_MS	20
+#define JC_SUBCMD_RATE_LIMITER_BT_MS	60
+#define JC_SUBCMD_RATE_LIMITER_MS(ctlr)	((ctlr)->hdev->bus == BUS_USB ? JC_SUBCMD_RATE_LIMITER_USB_MS : JC_SUBCMD_RATE_LIMITER_BT_MS)
 static void joycon_enforce_subcmd_rate(struct joycon_ctlr *ctlr)
 {
-	static const unsigned int max_subcmd_rate_ms = 25;
-	unsigned int current_ms = jiffies_to_msecs(jiffies);
-	unsigned int delta_ms = current_ms - ctlr->last_subcmd_sent_msecs;
+	unsigned int current_ms;
+	unsigned long subcmd_delta;
+	int consecutive_valid_deltas = 0;
+	int attempts = 0;
+	unsigned long flags;
+
+	if (unlikely(ctlr->ctlr_state != JOYCON_CTLR_STATE_READ))
+		return;
 
-	while (delta_ms < max_subcmd_rate_ms &&
-	       ctlr->ctlr_state == JOYCON_CTLR_STATE_READ) {
+	do {
 		joycon_wait_for_input_report(ctlr);
 		current_ms = jiffies_to_msecs(jiffies);
-		delta_ms = current_ms - ctlr->last_subcmd_sent_msecs;
+		subcmd_delta = current_ms - ctlr->last_subcmd_sent_msecs;
+
+		spin_lock_irqsave(&ctlr->lock, flags);
+		consecutive_valid_deltas = ctlr->consecutive_valid_report_deltas;
+		spin_unlock_irqrestore(&ctlr->lock, flags);
+
+		attempts++;
+	} while ((consecutive_valid_deltas < JC_SUBCMD_VALID_DELTA_REQ ||
+		  subcmd_delta < JC_SUBCMD_RATE_LIMITER_MS(ctlr)) &&
+		 ctlr->ctlr_state == JOYCON_CTLR_STATE_READ &&
+		 attempts < JC_SUBCMD_RATE_MAX_ATTEMPTS);
+
+	if (attempts >= JC_SUBCMD_RATE_MAX_ATTEMPTS) {
+		hid_warn(ctlr->hdev, "%s: exceeded max attempts", __func__);
+		return;
 	}
+
 	ctlr->last_subcmd_sent_msecs = current_ms;
+
+	/*
+	 * Wait a short time after receiving an input report before
+	 * transmitting. This should reduce odds of a TX coinciding with an RX.
+	 * Minimizing concurrent BT traffic with the controller seems to lower
+	 * the rate of disconnections.
+	 */
+	msleep(JC_SUBCMD_TX_OFFSET_MS);
 }
 
 static int joycon_hid_send_sync(struct joycon_ctlr *ctlr, u8 *data, size_t len,
@@ -1223,6 +1260,7 @@ static void joycon_parse_report(struct joycon_ctlr *ctlr,
 	u8 tmp;
 	u32 btns;
 	unsigned long msecs = jiffies_to_msecs(jiffies);
+	unsigned long report_delta_ms = msecs - ctlr->last_input_report_msecs;
 
 	spin_lock_irqsave(&ctlr->lock, flags);
 	if (IS_ENABLED(CONFIG_NINTENDO_FF) && rep->vibrator_report &&
@@ -1364,6 +1402,31 @@ static void joycon_parse_report(struct joycon_ctlr *ctlr,
 
 	input_sync(dev);
 
+	spin_lock_irqsave(&ctlr->lock, flags);
+	ctlr->last_input_report_msecs = msecs;
+	/*
+	 * Was this input report a reasonable time delta compared to the prior
+	 * report? We use this information to decide when a safe time is to send
+	 * rumble packets or subcommand packets.
+	 */
+	if (report_delta_ms >= JC_INPUT_REPORT_MIN_DELTA &&
+	    report_delta_ms <= JC_INPUT_REPORT_MAX_DELTA) {
+		if (ctlr->consecutive_valid_report_deltas < JC_SUBCMD_VALID_DELTA_REQ)
+			ctlr->consecutive_valid_report_deltas++;
+	} else {
+		ctlr->consecutive_valid_report_deltas = 0;
+	}
+	/*
+	 * Our consecutive valid report tracking is only relevant for
+	 * bluetooth-connected controllers. For USB devices, we're beholden to
+	 * USB's underlying polling rate anyway. Always set to the consecutive
+	 * delta requirement.
+	 */
+	if (ctlr->hdev->bus == BUS_USB)
+		ctlr->consecutive_valid_report_deltas = JC_SUBCMD_VALID_DELTA_REQ;
+
+	spin_unlock_irqrestore(&ctlr->lock, flags);
+
 	/*
 	 * Immediately after receiving a report is the most reliable time to
 	 * send a subcommand to the controller. Wake any subcommand senders