Bluetooth: Add support for Shorter Connection Interval (SCI) feature

Add HCI command, event and feature bit definitions for the Bluetooth
6.2 Shorter Connection Interval feature:

Commands:
 - HCI_OP_LE_CONN_RATE (0x20a1) - Connection Rate Request
 - HCI_OP_LE_SET_DEF_RATE (0x20a2) - Set Default Rate Parameters
 - HCI_OP_LE_READ_CONN_INTERVAL (0x20a3) - Read Min Supported
   Connection Interval

Events:
 - HCI_EVT_LE_CONN_RATE_CHANGE (0x37) - Connection Rate Change

Feature bits:
 - HCI_LE_SCI - Shorter Connection Intervals
 - HCI_LE_SCI_HOST - Shorter Connection Intervals (Host Support)

During controller init, when SCI is supported:
 - Set Shorter Connection Intervals (Host Support) feature via
   LE Set Host Feature
 - Read Minimum Supported Connection Interval
 - Set Default Rate Parameters

The Connection Rate Change event handler updates the connection
interval, latency and supervision timeout on the hci_conn.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

include/net/bluetooth/hci.h

@@ -653,6 +653,8 @@ enum {
 #define HCI_LE_LL_EXT_FEATURE		0x80
 #define HCI_LE_CS			0x40
 #define HCI_LE_CS_HOST			0x80
+#define HCI_LE_SCI			0x01	/* byte 9 - Shorter Connection Intervals */
+#define HCI_LE_SCI_HOST			0x02	/* byte 9 - Shorter Connection Intervals (Host) */
 
 /* Connection modes */
 #define HCI_CM_ACTIVE	0x0000
@@ -2489,6 +2491,46 @@ struct hci_cp_le_set_host_feature_v2 {
 	__u8	bit_value;
 } __packed;
 
+#define HCI_OP_LE_CONN_RATE			0x20a1
+struct hci_cp_le_conn_rate {
+	__le16	handle;
+	__le16	interval_min;
+	__le16	interval_max;
+	__le16	subrate_min;
+	__le16	subrate_max;
+	__le16	max_latency;
+	__le16	cont_num;
+	__le16	supv_timeout;
+	__le16	min_ce_len;
+	__le16	max_ce_len;
+} __packed;
+
+#define HCI_OP_LE_SET_DEF_RATE			0x20a2
+struct hci_cp_le_set_def_rate {
+	__le16	interval_min;
+	__le16	interval_max;
+	__le16	subrate_min;
+	__le16	subrate_max;
+	__le16	max_latency;
+	__le16	cont_num;
+	__le16	supv_timeout;
+	__le16	min_ce_len;
+	__le16	max_ce_len;
+} __packed;
+
+#define HCI_OP_LE_READ_CONN_INTERVAL		0x20a3
+struct hci_le_conn_interval_group {
+	__le16	min;
+	__le16	max;
+	__le16	stride;
+} __packed;
+
+struct hci_rp_le_read_conn_interval {
+	__u8	status;
+	__u8	num_grps;
+	struct hci_le_conn_interval_group grps[];
+} __packed;
+
 /* ---- HCI Events ---- */
 struct hci_ev_status {
 	__u8    status;
@@ -3303,6 +3345,17 @@ struct hci_evt_le_cs_test_end_complete {
 	__u8	status;
 } __packed;
 
+#define HCI_EVT_LE_CONN_RATE_CHANGE			0x37
+struct hci_evt_le_conn_rate_change {
+	__u8	status;
+	__le16	handle;
+	__le16	interval;
+	__le16	subrate;
+	__le16	latency;
+	__le16	cont_number;
+	__le16	supv_timeout;
+} __packed;
+
 #define HCI_EV_VENDOR			0xff
 
 /* Internal events generated by Bluetooth stack */

include/net/bluetooth/hci_core.h

@@ -416,6 +416,7 @@ struct hci_dev {
 	__u16		le_conn_max_interval;
 	__u16		le_conn_latency;
 	__u16		le_supv_timeout;
+	__u16		le_min_rate_interval;
 	__u16		le_def_tx_len;
 	__u16		le_def_tx_time;
 	__u16		le_max_tx_len;
@@ -720,6 +721,11 @@ struct hci_conn {
 	__u16		le_conn_interval;
 	__u16		le_conn_latency;
 	__u16		le_supv_timeout;
+	__u16		le_rate_interval;
+	__u16		le_subrate;
+	__u16		le_rate_latency;
+	__u16		le_cont_num;
+	__u16		le_rate_supv_timeout;
 	__u8		le_adv_data[HCI_MAX_EXT_AD_LENGTH];
 	__u8		le_adv_data_len;
 	__u8		le_per_adv_data[HCI_MAX_PER_AD_TOT_LEN];
@@ -2079,6 +2085,9 @@ void hci_conn_del_sysfs(struct hci_conn *conn);
 #define le_cs_host_capable(dev) \
 	((dev)->le_features[5] & HCI_LE_CS_HOST)
 
+#define le_sci_capable(dev) \
+	((dev)->le_features[9] & HCI_LE_SCI)
+
 #define mws_transport_config_capable(dev) (((dev)->commands[30] & 0x08) && \
 	(!hci_test_quirk((dev), HCI_QUIRK_BROKEN_MWS_TRANSPORT_CONFIG)))
 

net/bluetooth/hci_event.c

@@ -1241,6 +1241,39 @@ static u8 hci_cc_le_read_local_features(struct hci_dev *hdev, void *data,
 	return rp->status;
 }
 
+static u8 hci_cc_le_read_conn_interval(struct hci_dev *hdev, void *data,
+				       struct sk_buff *skb)
+{
+	struct hci_rp_le_read_conn_interval *rp = data;
+	u16 min_interval = 0;
+	int i;
+
+	bt_dev_dbg(hdev, "status 0x%2.2x", rp->status);
+
+	if (rp->status)
+		return rp->status;
+
+	if (skb->len < flex_array_size(rp, grps, rp->num_grps)) {
+		bt_dev_err(hdev, "Invalid response length for 0x%4.4x",
+			   HCI_OP_LE_READ_CONN_INTERVAL);
+		return HCI_ERROR_UNSPECIFIED;
+	}
+
+	/* Store the smallest minimum supported connection interval reported by
+	 * the controller so the default rate parameters can be clamped to it.
+	 */
+	for (i = 0; i < rp->num_grps; i++) {
+		u16 min = le16_to_cpu(rp->grps[i].min);
+
+		if (!min_interval || min < min_interval)
+			min_interval = min;
+	}
+
+	hdev->le_min_rate_interval = min_interval;
+
+	return rp->status;
+}
+
 static u8 hci_cc_le_read_adv_tx_power(struct hci_dev *hdev, void *data,
 				      struct sk_buff *skb)
 {
@@ -4153,6 +4186,9 @@ static const struct hci_cc {
 	       sizeof(struct hci_rp_le_read_buffer_size)),
 	HCI_CC(HCI_OP_LE_READ_LOCAL_FEATURES, hci_cc_le_read_local_features,
 	       sizeof(struct hci_rp_le_read_local_features)),
+	HCI_CC_VL(HCI_OP_LE_READ_CONN_INTERVAL, hci_cc_le_read_conn_interval,
+		  sizeof(struct hci_rp_le_read_conn_interval),
+		  HCI_MAX_EVENT_SIZE),
 	HCI_CC(HCI_OP_LE_READ_ADV_TX_POWER, hci_cc_le_read_adv_tx_power,
 	       sizeof(struct hci_rp_le_read_adv_tx_power)),
 	HCI_CC(HCI_OP_USER_CONFIRM_REPLY, hci_cc_user_confirm_reply,
@@ -7363,6 +7399,31 @@ static void hci_le_read_all_remote_features_evt(struct hci_dev *hdev,
 	hci_dev_unlock(hdev);
 }
 
+static void hci_le_conn_rate_change_evt(struct hci_dev *hdev, void *data,
+					struct sk_buff *skb)
+{
+	struct hci_evt_le_conn_rate_change *ev = data;
+	struct hci_conn *conn;
+
+	bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
+
+	if (ev->status)
+		return;
+
+	hci_dev_lock(hdev);
+
+	conn = hci_conn_hash_lookup_handle(hdev, __le16_to_cpu(ev->handle));
+	if (conn) {
+		conn->le_rate_interval = le16_to_cpu(ev->interval);
+		conn->le_subrate = le16_to_cpu(ev->subrate);
+		conn->le_rate_latency = le16_to_cpu(ev->latency);
+		conn->le_cont_num = le16_to_cpu(ev->cont_number);
+		conn->le_rate_supv_timeout = le16_to_cpu(ev->supv_timeout);
+	}
+
+	hci_dev_unlock(hdev);
+}
+
 #define HCI_LE_EV_VL(_op, _func, _min_len, _max_len) \
 [_op] = { \
 	.func = _func, \
@@ -7474,6 +7535,9 @@ static const struct hci_le_ev {
 		     sizeof(struct
 			    hci_evt_le_read_all_remote_features_complete),
 		     HCI_MAX_EVENT_SIZE),
+	/* [0x37 = HCI_EVT_LE_CONN_RATE_CHANGE] */
+	HCI_LE_EV(HCI_EVT_LE_CONN_RATE_CHANGE, hci_le_conn_rate_change_evt,
+		  sizeof(struct hci_evt_le_conn_rate_change)),
 };
 
 static void hci_le_meta_evt(struct hci_dev *hdev, void *data,

net/bluetooth/hci_sync.c

@@ -4541,6 +4541,10 @@ static int hci_le_set_event_mask_sync(struct hci_dev *hdev)
 		events[6] |= 0x02;	/* LE CS Subevent Result Continue event */
 		events[6] |= 0x04;	/* LE CS Test End Complete event */
 	}
+
+	if (le_sci_capable(hdev))
+		events[6] |= 0x40;	/* LE Connection Rate Change event */
+
 	return __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_EVENT_MASK,
 				     sizeof(events), events, HCI_CMD_TIMEOUT);
 }
@@ -4709,12 +4713,59 @@ static int hci_le_set_host_feature_sync(struct hci_dev *hdev, u16 bit, u8 value)
 				     sizeof(cp), &cp, HCI_CMD_TIMEOUT);
 }
 
+static int hci_le_read_conn_interval_sync(struct hci_dev *hdev)
+{
+	if (!le_sci_capable(hdev))
+		return 0;
+
+	return __hci_cmd_sync_status(hdev, HCI_OP_LE_READ_CONN_INTERVAL,
+				     0, NULL, HCI_CMD_TIMEOUT);
+}
+
+static int hci_le_set_def_rate_sync(struct hci_dev *hdev)
+{
+	struct hci_cp_le_set_def_rate cp;
+	u16 interval_min = 0x000a;	/* 1.25 ms */
+	u16 interval_max = 0x0078;	/* 15 ms */
+
+	if (!le_sci_capable(hdev))
+		return 0;
+
+	/* Clamp the interval range to the controller's minimum supported
+	 * connection interval (read via HCI_OP_LE_READ_CONN_INTERVAL) so the
+	 * default rate parameters are not rejected. The maximum is raised as
+	 * well if needed to keep interval_min <= interval_max.
+	 */
+	if (hdev->le_min_rate_interval > interval_min) {
+		interval_min = hdev->le_min_rate_interval;
+		if (interval_min > interval_max)
+			interval_max = interval_min;
+	}
+
+	memset(&cp, 0, sizeof(cp));
+
+	/* Use the HIDS 1.2 recommended Full Range mode values as the default
+	 * rate parameters (see HOGP v1.2 spec). Connection intervals are in
+	 * units of 0.125 ms and the supervision timeout is in units of 10 ms.
+	 */
+	cp.interval_min = cpu_to_le16(interval_min);
+	cp.interval_max = cpu_to_le16(interval_max);
+	cp.subrate_min = cpu_to_le16(0x0001);
+	cp.subrate_max = cpu_to_le16(0x0004);
+	cp.max_latency = cpu_to_le16(0x0000);
+	cp.cont_num = cpu_to_le16(0x0001);
+	cp.supv_timeout = cpu_to_le16(0x000c);	/* 120 ms */
+
+	return __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_DEF_RATE,
+				     sizeof(cp), &cp, HCI_CMD_TIMEOUT);
+}
+
 /* Set Host Features, each feature needs to be sent separately since
  * HCI_OP_LE_SET_HOST_FEATURE doesn't support setting all of them at once.
  */
 static int hci_le_set_host_features_sync(struct hci_dev *hdev)
 {
-	int err;
+	int err = 0;
 
 	if (cis_capable(hdev)) {
 		/* Connected Isochronous Channels (Host Support) */
@@ -4725,9 +4776,16 @@ static int hci_le_set_host_features_sync(struct hci_dev *hdev)
 			return err;
 	}
 
-	if (le_cs_capable(hdev))
+	if (le_cs_capable(hdev)) {
 		/* Channel Sounding (Host Support) */
 		err = hci_le_set_host_feature_sync(hdev, 47, 0x01);
+		if (err)
+			return err;
+	}
+
+	if (le_sci_capable(hdev))
+		/* Shorter Connection Intervals (Host Support) */
+		err = hci_le_set_host_feature_sync(hdev, 73, 0x01);
 
 	return err;
 }
@@ -4760,6 +4818,10 @@ static const struct hci_init_stage le_init3[] = {
 	HCI_INIT(hci_set_le_support_sync),
 	/* HCI_OP_LE_SET_HOST_FEATURE */
 	HCI_INIT(hci_le_set_host_features_sync),
+	/* HCI_OP_LE_READ_CONN_INTERVAL */
+	HCI_INIT(hci_le_read_conn_interval_sync),
+	/* HCI_OP_LE_SET_DEF_RATE */
+	HCI_INIT(hci_le_set_def_rate_sync),
 	{}
 };