From patchwork Wed Feb 19 18:13:32 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pauli Virtanen X-Patchwork-Id: 13982614 Received: from meesny.iki.fi (meesny.iki.fi [195.140.195.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6D1041A7264; Wed, 19 Feb 2025 18:13:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=195.140.195.201 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739988836; cv=pass; b=FwOTDlBfRaliUSr1rrVMq3bjm1bDCajAZQ+77dyigKaXOOy+sQbe6ESQoHK7O3B+a2QilrbVCKEGpdbY1kMTWnHHrhz3qTBc18UjuPVkfnsBJeNZvcAAFVqrTDU+FP+fwwEWiuog/t6mdzOoa9OH+wdukA24Ti7nyHsiZd2JzXo= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739988836; c=relaxed/simple; bh=H3WFiZ6Lg19AdQqBFHLqhRqZsA/ZRyzUZwtPyPfU6BU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=EU/uTO+wkX3QCKxRahvIBtY37bWg1/0vGHWMHZnTFypvvW2YsCc5A4oKQkI0CNFr6EFB9EPIuHviq60DDfVTaH9LUyuJN8cul3NE/mDQemYOveR+SVgzgksyy474TlhgofjJD34wO0UjZSitaXxDQznUulOQHM3ncHn9paeeDp8= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=iki.fi; spf=pass smtp.mailfrom=iki.fi; dkim=pass (1024-bit key) header.d=iki.fi header.i=@iki.fi header.b=RFZU5qVH; arc=pass smtp.client-ip=195.140.195.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=iki.fi Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=iki.fi Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=iki.fi header.i=@iki.fi header.b="RFZU5qVH" Received: from monolith.lan (unknown [193.138.7.178]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: pav) by meesny.iki.fi (Postfix) with ESMTPSA id 4YykzW3cCvzyQQ; Wed, 19 Feb 2025 20:13:43 +0200 (EET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=iki.fi; s=meesny; t=1739988826; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=hOkm928FH1MXpDJcxJZjAaAV4tVx2mcqhCypx8RXFKo=; b=RFZU5qVHVP7l6n//421bwYECDfZx7wSxoigACfkpE7YUWchicIImxE82CGnpke1AciWj10 +qPggQi/TbLADK/2zhfkmT22whWflD57ESu0tZnteOJypH/+ZuKBMbAe8zcpjUz6E1CMSN A463+0Anepsi6TqpJyaFXD7RdSyM/Co= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=iki.fi; s=meesny; t=1739988826; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=hOkm928FH1MXpDJcxJZjAaAV4tVx2mcqhCypx8RXFKo=; b=oPUNjtQsW1AFibX6fSlgcigzFZFdXlBGarcDDE7dI2bS0vRRERki0C8wbkOZ5/ERnZ7kKb EDOzSapB84e283tnCD1FvyMNPEYJ2lfEBZFrmaHh9Qra2YdOgjUQtcy8pDnBHVEJENN/Rg Fnr2GlBN3APsq4segiFDR1dSsQL4d6M= ARC-Authentication-Results: i=1; ORIGINATING; auth=pass smtp.auth=pav smtp.mailfrom=pav@iki.fi ARC-Seal: i=1; s=meesny; d=iki.fi; t=1739988826; a=rsa-sha256; cv=none; b=QOvH79VUMMuz8bj+8ZIAE09MBNXRBOmkc90nxaWIoVUwebqVV178TIidCWXRfA6+c47gDk Shv7u5U+s6TDrxMGmZIUwFD++0IARIH2X4ykm7YE9m6uzL1wSAJVzvPzhcaScKj/WAIGP9 sGDnJUPx1FqZF6CJGj1XLX7h9yMKbI8= From: Pauli Virtanen To: linux-bluetooth@vger.kernel.org Cc: Pauli Virtanen , Luiz Augusto von Dentz , netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, willemdebruijn.kernel@gmail.com Subject: [PATCH v4 0/5] net: Bluetooth: add TX timestamping for ISO/L2CAP/SCO Date: Wed, 19 Feb 2025 20:13:32 +0200 Message-ID: X-Mailer: git-send-email 2.48.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add support for TX timestamping in Bluetooth ISO/L2CAP/SCO sockets. Add new COMPLETION timestamp type, to report a software timestamp when the hardware reports a packet completed. (Cc netdev for this) Previous discussions: https://lore.kernel.org/linux-bluetooth/cover.1739097311.git.pav@iki.fi/ https://lore.kernel.org/all/6642c7f3427b5_20539c2949a@willemb.c.googlers.com.notmuch/ https://lore.kernel.org/all/cover.1710440392.git.pav@iki.fi/ Changes ======= v4: - Change meaning of SOF_TIMESTAMPING_TX_COMPLETION, to save a bit in skb_shared_info.tx_flags: It now enables COMPLETION only for packets that also have software SND enabled. The flag can now be enabled only via a socket option, but coupling with SND allows user to still choose for which packets SND+COMPLETION should be generated. This choice maybe is OK for applications which can skip SND if they're not interested. However, this would make the timestamping API not uniform, as the other TX flags can be enabled via CMSG. IIUC, sizeof skb_shared_info cannot be easily changed and I'm not sure there is somewhere else in general skb info, where one could safely put the extra separate flag bit for COMPLETION. So here's alternative suggestion. - Better name in sof_timestamping_names - I decided to keep using sockcm_init(), to avoid open coding READ_ONCE and since it's passed to sock_cmsg_send() which anyway also may init such fields. v3: - Add new COMPLETION timestamp type, and emit it in HCI completion. - Emit SND instead of SCHED, when sending to driver. - Do not emit SCHED timestamps. - Don't safeguard tx_q length explicitly. Now that hci_sched_acl_blk() is no more, the scheduler flow control is guaranteed to keep it bounded. - Fix L2CAP stream sockets to use the bytestream timestamp conventions. Overview ======== The packet flow in Bluetooth is the following. Timestamps added here indicated: user sendmsg() generates skbs | * skb waits in net/bluetooth queue for a free HW packet slot | * orphan skb, send to driver -> TSTAMP_SND | * driver: send packet data to transport (eg. USB) | * wait for transport completion | * driver: transport tx completion, free skb (some do this immediately) | * packet waits in HW side queue | * HCI report for packet completion -> TSTAMP_COMPLETION (for non-SCO) In addition, we may want to do the following in future (but not implemented in this series as we don't have ISO sequence number synchronization yet which is needed first, moreover e.g. Intel controllers return only zeros in timestamps): * if packet is ISO, send HCI LE Read ISO TX Sync | * HCI response -> hardware TSTAMP_SND for the packet the response corresponds to if it was waiting for one, might not be possible to get a tstamp for every packet Bluetooth does not have tx timestamps in the completion reports from hardware, and only for ISO packets there are HCI commands in specification for querying timestamps afterward. The drivers do not provide ways to get timestamps either, I'm also not aware if some devices would have vendor-specific commands to get them. Driver-side timestamps ====================== Generating SND on driver side may be slightly more accurate, but that requires changing the BT driver API to not orphan skbs first. In theory this probably won't cause problems, but it is not done in this patchset. For some of the drivers it won't gain much. E.g. btusb immediately submits the URB, so if one would emit SND just before submit (as drivers/net/usb/usbnet.c does), it is essentially identical to emitting before sending to driver. btintel_pcie looks like it does synchronous send, so looks the same. hci_serdev has internal queue, iiuc flushing as fast as data can be transferred, but it shouldn't be waiting for hardware slots due to HCI flow control. Unless HW buffers are full, packets mostly wait on the HW side. E.g. with btusb (non-SCO) median time from sendmsg() to URB generation is ~0.1 ms, to USB completion ~0.5 ms, and HCI completion report at ~5 ms. The exception is SCO, for which HCI flow control is disabled, so they do not get completion events so it's possible to build up queues inside the driver. For SCO, COMPLETION needs to be generated from driver side, eg. for btusb maybe at URB completion. This could be useful for SCO PCM modes (but which are more or less obsolete nowadays), where USB isoc data rate matches audio data rate, so queues on USB side may build up. Use cases ========= In audio use cases we want to track and avoid queues building up, to control latency, especially in cases like ISO where the controller has a fixed schedule that the sending application must match. E.g. application can aim to keep 1 packet in HW queue, so it has 2*7.5ms of slack for being woken up too late. Applications can use SND & COMPLETION timestamps to track in-kernel and in-HW packet queues separately. This can matter for ISO, where the specification allows HW to use the timings when it gets packets to determine what packets are synchronized together. Applications can use SND to track that. Tests ===== See https://lore.kernel.org/linux-bluetooth/cover.1739026302.git.pav@iki.fi/ Pauli Virtanen (5): net-timestamp: COMPLETION timestamp on packet tx completion Bluetooth: add support for skb TX SND/COMPLETION timestamping Bluetooth: ISO: add TX timestamping Bluetooth: L2CAP: add TX timestamping Bluetooth: SCO: add TX timestamping socket-level mechanism Documentation/networking/timestamping.rst | 9 ++ include/net/bluetooth/bluetooth.h | 1 + include/net/bluetooth/hci_core.h | 13 +++ include/net/bluetooth/l2cap.h | 3 +- include/uapi/linux/errqueue.h | 1 + include/uapi/linux/net_tstamp.h | 6 +- net/bluetooth/6lowpan.c | 2 +- net/bluetooth/hci_conn.c | 118 ++++++++++++++++++++++ net/bluetooth/hci_core.c | 17 +++- net/bluetooth/hci_event.c | 4 + net/bluetooth/iso.c | 24 ++++- net/bluetooth/l2cap_core.c | 41 +++++++- net/bluetooth/l2cap_sock.c | 15 ++- net/bluetooth/sco.c | 19 +++- net/bluetooth/smp.c | 2 +- net/core/sock.c | 2 + net/ethtool/common.c | 1 + 17 files changed, 258 insertions(+), 20 deletions(-)