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Subject: Re: [RFC PATCH v4 3/5] Bluetooth: Handle BR/EDR devices during
 suspend
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20200303170610.RFC.v4.3.Icc7c35e1cabf10f8a383a009694987520f1d1b35@changeid>
Date:   Sun, 8 Mar 2020 09:30:30 +0100
Cc:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Alain Michaud <alainm@chromium.org>,
        linux-bluetooth@vger.kernel.org,
        chromeos-bluetooth-upstreaming@chromium.org,
        "David S. Miller" <davem@davemloft.net>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jakub Kicinski <kuba@kernel.org>
Content-Transfer-Encoding: 8BIT
Message-Id: <52D3794C-88F4-4A6D-9E64-98CC1AAC058F@holtmann.org>
References: <20200304010650.259961-1-abhishekpandit@chromium.org>
 <20200303170610.RFC.v4.3.Icc7c35e1cabf10f8a383a009694987520f1d1b35@changeid>
To:     Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Abhishek,

> To handle BR/EDR devices, we first disable page scan and disconnect all
> connected devices. Once that is complete, we add event filters (for
> devices that can wake the system) and re-enable page scan.
> 
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> ---
> 
> Changes in v4: None
> Changes in v3:
> * Refactored to only handle BR/EDR devices
> 
> Changes in v2:
> * Refactored filters and whitelist settings to its own patch
> * Refactored update_white_list to have clearer edge cases
> * Add connected devices to whitelist (previously missing corner case)
> 
> include/net/bluetooth/hci.h      |  17 ++++--
> include/net/bluetooth/hci_core.h |   9 ++-
> net/bluetooth/hci_core.c         |  21 ++++++-
> net/bluetooth/hci_event.c        |  24 ++++++++
> net/bluetooth/hci_request.c      | 101 +++++++++++++++++++++++++++++++
> 5 files changed, 162 insertions(+), 10 deletions(-)
> 
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index 0b3ebd35681d..414f91dec221 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -941,10 +941,14 @@ struct hci_cp_sniff_subrate {
> #define HCI_OP_RESET			0x0c03
> 
> #define HCI_OP_SET_EVENT_FLT		0x0c05
> -struct hci_cp_set_event_flt {
> -	__u8     flt_type;
> -	__u8     cond_type;
> -	__u8     condition[];
> +#define HCI_SET_EVENT_FLT_SIZE		9
> +struct hci_cp_set_event_filter {
> +	__u8		flt_type;
> +	__u8		cond_type;
> +	struct {
> +		bdaddr_t bdaddr;
> +		__u8 auto_accept;
> +	} __packed	addr_conn_flt;
> } __packed;
> 
> /* Filter types */
> @@ -958,8 +962,9 @@ struct hci_cp_set_event_flt {
> #define HCI_CONN_SETUP_ALLOW_BDADDR	0x02
> 
> /* CONN_SETUP Conditions */
> -#define HCI_CONN_SETUP_AUTO_OFF	0x01
> -#define HCI_CONN_SETUP_AUTO_ON	0x02
> +#define HCI_CONN_SETUP_AUTO_OFF		0x01
> +#define HCI_CONN_SETUP_AUTO_ON		0x02
> +#define HCI_CONN_SETUP_AUTO_ON_WITH_RS	0x03
> 
> #define HCI_OP_READ_STORED_LINK_KEY	0x0c0d
> struct hci_cp_read_stored_link_key {
> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> index b82a89b88d1b..4eb5b2786048 100644
> --- a/include/net/bluetooth/hci_core.h
> +++ b/include/net/bluetooth/hci_core.h
> @@ -91,6 +91,10 @@ struct discovery_state {
> #define SUSPEND_NOTIFIER_TIMEOUT	msecs_to_jiffies(2000) /* 2 seconds */
> 
> enum suspend_tasks {
> +	SUSPEND_SCAN_DISABLE,
> +	SUSPEND_SCAN_ENABLE,
> +	SUSPEND_DISCONNECTING,
> +
> 	SUSPEND_POWERING_DOWN,
> 
> 	SUSPEND_PREPARE_NOTIFIER,
> @@ -99,7 +103,8 @@ enum suspend_tasks {
> 
> enum suspended_state {
> 	BT_RUNNING = 0,
> -	BT_SUSPENDED,
> +	BT_SUSPEND_DISCONNECT,
> +	BT_SUSPEND_COMPLETE,
> };
> 
> struct hci_conn_hash {
> @@ -408,6 +413,8 @@ struct hci_dev {
> 	struct work_struct	suspend_prepare;
> 	enum suspended_state	suspend_state_next;
> 	enum suspended_state	suspend_state;
> +	bool			scanning_paused;
> +	bool			suspended;
> 
> 	wait_queue_head_t	suspend_wait_q;
> 	DECLARE_BITMAP(suspend_tasks, __SUSPEND_NUM_TASKS);
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index ad89ff3f8f57..72e53fde2a74 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -3302,16 +3302,31 @@ static int hci_suspend_notifier(struct notifier_block *nb, unsigned long action,
> 		goto done;
> 
> 	if (action == PM_SUSPEND_PREPARE) {
> -		hdev->suspend_state_next = BT_SUSPENDED;
> +		/* Suspend consists of two actions:
> +		 *  - First, disconnect everything and make the controller not
> +		 *    connectable (disabling scanning)
> +		 *  - Second, program event filter/whitelist and enable scan
> +		 */
> +		hdev->suspend_state_next = BT_SUSPEND_DISCONNECT;
> 		set_bit(SUSPEND_PREPARE_NOTIFIER, hdev->suspend_tasks);
> 		queue_work(hdev->req_workqueue, &hdev->suspend_prepare);
> -
> 		ret = hci_suspend_wait_event(hdev);
> +
> +		/* If the disconnect portion failed, don't attempt to complete
> +		 * by configuring the whitelist. The suspend notifier will
> +		 * follow a cancelled suspend with a PM_POST_SUSPEND
> +		 * notification.
> +		 */
> +		if (!ret) {
> +			hdev->suspend_state_next = BT_SUSPEND_COMPLETE;
> +			set_bit(SUSPEND_PREPARE_NOTIFIER, hdev->suspend_tasks);
> +			queue_work(hdev->req_workqueue, &hdev->suspend_prepare);
> +			ret = hci_suspend_wait_event(hdev);
> +		}
> 	} else if (action == PM_POST_SUSPEND) {
> 		hdev->suspend_state_next = BT_RUNNING;
> 		set_bit(SUSPEND_PREPARE_NOTIFIER, hdev->suspend_tasks);
> 		queue_work(hdev->req_workqueue, &hdev->suspend_prepare);
> -
> 		ret = hci_suspend_wait_event(hdev);
> 	}
> 
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 591e7477e925..e3c36230f705 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -2474,6 +2474,7 @@ static void hci_inquiry_result_evt(struct hci_dev *hdev, struct sk_buff *skb)
> static void hci_conn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb)
> {
> 	struct hci_ev_conn_complete *ev = (void *) skb->data;
> +	struct inquiry_entry *ie;
> 	struct hci_conn *conn;
> 
> 	BT_DBG("%s", hdev->name);
> @@ -2482,6 +2483,21 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb)
> 
> 	conn = hci_conn_hash_lookup_ba(hdev, ev->link_type, &ev->bdaddr);
> 	if (!conn) {
> +		/* Connection may not exist if auto-connected. Check the inquiry
> +		 * cache to see if we've already discovered this bdaddr before.
> +		 * If found and link is an ACL type, create a connection class
> +		 * automatically.
> +		 */
> +		ie = hci_inquiry_cache_lookup(hdev, &ev->bdaddr);
> +		if (ie && ev->link_type == ACL_LINK) {
> +			conn = hci_conn_add(hdev, ev->link_type, &ev->bdaddr,
> +					    HCI_ROLE_SLAVE);
> +			if (!conn) {
> +				bt_dev_err(hdev, "no memory for new conn");
> +				goto unlock;
> +			}
> +		}
> +
> 		if (ev->link_type != SCO_LINK)
> 			goto unlock;
> 
> @@ -2743,6 +2759,14 @@ static void hci_disconn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb)
> 	hci_disconn_cfm(conn, ev->reason);
> 	hci_conn_del(conn);
> 
> +	/* The suspend notifier is waiting for all devices to disconnect so
> +	 * clear the bit from pending tasks and inform the wait queue.
> +	 */
> +	if (list_empty(&hdev->conn_hash.list) &&
> +	    test_and_clear_bit(SUSPEND_DISCONNECTING, hdev->suspend_tasks)) {
> +		wake_up(&hdev->suspend_wait_q);
> +	}
> +
> 	/* Re-enable advertising if necessary, since it might
> 	 * have been disabled by the connection. From the
> 	 * HCI_LE_Set_Advertise_Enable command description in
> diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
> index 08908469c043..4d67b1d08608 100644
> --- a/net/bluetooth/hci_request.c
> +++ b/net/bluetooth/hci_request.c
> @@ -918,12 +918,62 @@ static u8 get_adv_instance_scan_rsp_len(struct hci_dev *hdev, u8 instance)
> 	return adv_instance->scan_rsp_len;
> }
> 
> +static void hci_req_clear_event_filter(struct hci_request *req)
> +{
> +	struct hci_cp_set_event_filter f;
> +
> +	memset(&f, 0, sizeof(f));
> +	f.flt_type = HCI_FLT_CLEAR_ALL;
> +	hci_req_add(req, HCI_OP_SET_EVENT_FLT, 1, &f);
> +
> +	/* Update page scan state (since we may have modified it when setting
> +	 * the event filter).
> +	 */
> +	__hci_req_update_scan(req);
> +}
> +
> +static void hci_req_set_event_filter(struct hci_request *req)
> +{
> +	struct bdaddr_list *b;
> +	struct hci_cp_set_event_filter f;
> +	struct hci_dev *hdev = req->hdev;
> +	u8 scan;
> +
> +	/* Always clear event filter when starting */
> +	hci_req_clear_event_filter(req);
> +
> +	list_for_each_entry(b, &hdev->wakeable, list) {
> +		memset(&f, 0, sizeof(f));
> +		bacpy(&f.addr_conn_flt.bdaddr, &b->bdaddr);
> +		f.flt_type = HCI_FLT_CONN_SETUP;
> +		f.cond_type = HCI_CONN_SETUP_ALLOW_BDADDR;
> +		f.addr_conn_flt.auto_accept = HCI_CONN_SETUP_AUTO_ON;
> +
> +		BT_DBG("Adding event filters for %pMR", &b->bdaddr);
> +		hci_req_add(req, HCI_OP_SET_EVENT_FLT, sizeof(f), &f);
> +	}
> +
> +	scan = !list_empty(&hdev->wakeable) ? SCAN_PAGE : SCAN_DISABLED;
> +	hci_req_add(req, HCI_OP_WRITE_SCAN_ENABLE, 1, &scan);
> +}
> +
> +static void suspend_req_complete(struct hci_dev *hdev, u8 status, u16 opcode)
> +{
> +	BT_DBG("Request complete opcode=0x%x, status=0x%x", opcode, status);
> +	if (test_and_clear_bit(SUSPEND_SCAN_ENABLE, hdev->suspend_tasks) ||
> +	    test_and_clear_bit(SUSPEND_SCAN_DISABLE, hdev->suspend_tasks)) {
> +		wake_up(&hdev->suspend_wait_q);
> +	}
> +}
> +
> /* Call with hci_dev_lock */
> void hci_req_prepare_suspend(struct hci_dev *hdev, enum suspended_state next)
> {
> 	int old_state;
> 	struct hci_conn *conn;
> 	struct hci_request req;
> +	u8 page_scan;
> +	int disconnect_counter;
> 
> 	if (next == hdev->suspend_state) {
> 		BT_DBG("Same state before and after: %d", next);
> @@ -931,6 +981,54 @@ void hci_req_prepare_suspend(struct hci_dev *hdev, enum suspended_state next)
> 	}
> 
> 	hdev->suspend_state = next;
> +	hci_req_init(&req, hdev);
> +
> +	if (next == BT_SUSPEND_DISCONNECT) {
> +		/* Mark device as suspended */
> +		hdev->suspended = true;
> +
> +		/* Disable page scan */
> +		page_scan = SCAN_DISABLED;
> +		hci_req_add(&req, HCI_OP_WRITE_SCAN_ENABLE, 1, &page_scan);
> +
> +		/* Mark task needing completion */
> +		set_bit(SUSPEND_SCAN_DISABLE, hdev->suspend_tasks);
> +
> +		/* Prevent disconnects from causing scanning to be re-enabled */
> +		hdev->scanning_paused = true;
> +
> +		/* Run commands before disconnecting */
> +		hci_req_run(&req, suspend_req_complete);
> +
> +		disconnect_counter = 0;
> +		/* Soft disconnect everything (power off) */
> +		list_for_each_entry(conn, &hdev->conn_hash.list, list) {
> +			hci_disconnect(conn, HCI_ERROR_REMOTE_POWER_OFF);
> +			disconnect_counter++;
> +		}
> +
> +		if (disconnect_counter > 0) {
> +			BT_DBG("Had %d disconnects. Will wait on them",
> +			       disconnect_counter);
> +			set_bit(SUSPEND_DISCONNECTING, hdev->suspend_tasks);
> +		}
> +	} else if (next == BT_SUSPEND_COMPLETE) {
> +		/* Unpause to take care of updating scanning params */
> +		hdev->scanning_paused = false;
> +		/* Enable event filter for paired devices */
> +		hci_req_set_event_filter(&req);
> +		/* Pause scan changes again. */
> +		hdev->scanning_paused = true;
> +		hci_req_run(&req, suspend_req_complete);
> +	} else {
> +		hdev->suspended = false;
> +		hdev->scanning_paused = false;
> +
> +		hci_req_clear_event_filter(&req);
> +		hci_req_run(&req, suspend_req_complete);
> +	}
> +
> +	hdev->suspend_state = next;
> 
> done:
> 	clear_bit(SUSPEND_PREPARE_NOTIFIER, hdev->suspend_tasks);
> @@ -2034,6 +2132,9 @@ void __hci_req_update_scan(struct hci_request *req)
> 	if (mgmt_powering_down(hdev))
> 		return;
> 
> +	if (hdev->scanning_paused)
> +		return;
> +
> 	if (hci_dev_test_flag(hdev, HCI_CONNECTABLE) ||
> 	    disconnected_whitelist_entries(hdev))
> 		scan = SCAN_PAGE;

looks good. Just fold the struct list_head wakeable; change from 1/5 into this and use bt_dev_dbg.

Regards

Marcel