From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC5B8C433F5 for ; Fri, 17 Sep 2021 12:35:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B8C3610E9 for ; Fri, 17 Sep 2021 12:35:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244348AbhIQMhU convert rfc822-to-8bit (ORCPT ); Fri, 17 Sep 2021 08:37:20 -0400 Received: from coyote.holtmann.net ([212.227.132.17]:60836 "EHLO mail.holtmann.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244280AbhIQMhT (ORCPT ); Fri, 17 Sep 2021 08:37:19 -0400 Received: from smtpclient.apple (p5b3d2185.dip0.t-ipconnect.de [91.61.33.133]) by mail.holtmann.org (Postfix) with ESMTPSA id AA9E7CED2C; Fri, 17 Sep 2021 14:35:52 +0200 (CEST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.13\)) Subject: Re: [PATCH] Bluetooth: btusb: Lower passive lescan interval on Marvell 88W8897 From: Marcel Holtmann In-Reply-To: <20210917122718.86776-1-verdre@v0yd.nl> Date: Fri, 17 Sep 2021 14:35:52 +0200 Cc: Amitkumar Karwar , Ganapathi Bhat , Xinming Hu , Kalle Valo , "David S. Miller" , Jakub Kicinski , Johan Hedberg , Luiz Augusto von Dentz , Tsuchiya Yuto , linux-wireless@vger.kernel.org, linux-bluetooth , open list , Maximilian Luz , Andy Shevchenko , =?utf-8?Q?Pali_Roh=C3=A1r?= Content-Transfer-Encoding: 8BIT Message-Id: References: <20210917122718.86776-1-verdre@v0yd.nl> To: =?utf-8?Q?Jonas_Dre=C3=9Fler?= X-Mailer: Apple Mail (2.3654.120.0.1.13) Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Hi Jonas, > The Marvell 88W8897 combined wifi and bluetooth card (pcie+usb version) > is used in a lot of Microsoft Surface devices, and all those devices > suffer from very low 2.4GHz wifi connection speeds while bluetooth is > enabled. The reason for that is that the default passive scanning > interval for Bluetooth Low Energy devices is quite high on Linux > (interval of 60 msec and scan window of 30 msec, see le_scan_interval > and le_scan_window in hci_core.c), and the Marvell chip is known for its > bad bt+wifi coexisting performance. > > So decrease that passive scan interval and make the scan window shorter > on this particular device to allow for spending more time transmitting > wifi signals: The new scan interval is 250 msec (0x190 * 0.625 msec) and > the new scan window is 6.25 msec (0xa * 0.625 msec). > > This change has a very large impact on the 2.4GHz wifi speeds and gets > it up to performance comparable with the Windows driver, which seems to > apply a similar quirk. > > The scan interval and scan window length were tested and found to work > very well with a bunch of Bluetooth Low Energy devices, including the > Surface Pen, a Bluetooth Speaker and two modern Bluetooth headphones. > All devices were discovered immediately after turning them on. Even > lower values were also tested, but these introduced longer delays until > devices get discovered. > > Signed-off-by: Jonas Dreßler > --- > drivers/bluetooth/btusb.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c > index 60d2fce59a71..05b11179c839 100644 > --- a/drivers/bluetooth/btusb.c > +++ b/drivers/bluetooth/btusb.c > @@ -59,6 +59,7 @@ static struct usb_driver btusb_driver; > #define BTUSB_WIDEBAND_SPEECH 0x400000 > #define BTUSB_VALID_LE_STATES 0x800000 > #define BTUSB_QCA_WCN6855 0x1000000 > +#define BTUSB_LOWER_LESCAN_INTERVAL 0x2000000 > #define BTUSB_INTEL_BROKEN_INITIAL_NCMD 0x4000000 > > static const struct usb_device_id btusb_table[] = { > @@ -356,6 +357,7 @@ static const struct usb_device_id blacklist_table[] = { > { USB_DEVICE(0x1286, 0x2044), .driver_info = BTUSB_MARVELL }, > { USB_DEVICE(0x1286, 0x2046), .driver_info = BTUSB_MARVELL }, > { USB_DEVICE(0x1286, 0x204e), .driver_info = BTUSB_MARVELL }, > + { USB_DEVICE(0x1286, 0x204c), .driver_info = BTUSB_LOWER_LESCAN_INTERVAL }, > > /* Intel Bluetooth devices */ > { USB_DEVICE(0x8087, 0x0025), .driver_info = BTUSB_INTEL_COMBINED }, > @@ -3813,6 +3815,19 @@ static int btusb_probe(struct usb_interface *intf, > if (id->driver_info & BTUSB_MARVELL) > hdev->set_bdaddr = btusb_set_bdaddr_marvell; > > + /* The Marvell 88W8897 combined wifi and bluetooth card is known for > + * very bad bt+wifi coexisting performance. > + * > + * Decrease the passive BT Low Energy scan interval a bit > + * (0x0190 * 0.625 msec = 250 msec) and make the scan window shorter > + * (0x000a * 0,625 msec = 6.25 msec). This allows for significantly > + * higher wifi throughput while passively scanning for BT LE devices. > + */ > + if (id->driver_info & BTUSB_LOWER_LESCAN_INTERVAL) { > + hdev->le_scan_interval = 0x0190; > + hdev->le_scan_window = 0x000a; > + } > + you can not do it this way. Modifying hci_dev internals from within the driver is not acceptable. Regards Marcel