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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04851C0032E for ; Wed, 25 Oct 2023 14:44:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234466AbjJYOoq (ORCPT ); Wed, 25 Oct 2023 10:44:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232800AbjJYOoo (ORCPT ); Wed, 25 Oct 2023 10:44:44 -0400 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by lindbergh.monkeyblade.net (Postfix) with SMTP id 79140B0 for ; Wed, 25 Oct 2023 07:44:42 -0700 (PDT) Received: (qmail 496317 invoked by uid 1000); 25 Oct 2023 10:44:41 -0400 Date: Wed, 25 Oct 2023 10:44:41 -0400 From: Alan Stern To: Hardik Gajjar Cc: gregkh@linuxfoundation.org, mathias.nyman@intel.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, erosca@de.adit-jv.com Subject: Re: [PATCH v5] usb: Reduce 'set_address' command timeout with a new quirk Message-ID: <2345e113-71cd-4cf2-b910-45dd1bca3f13@rowland.harvard.edu> References: <20231025141316.117514-1-hgajjar@de.adit-jv.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231025141316.117514-1-hgajjar@de.adit-jv.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 25, 2023 at 04:13:16PM +0200, Hardik Gajjar wrote: > This patch introduces a new USB quirk, USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT, > which modifies the timeout value for the 'set_address' command. The > standard timeout for this command is 5000 ms, as recommended in the USB > 3.2 specification (section 9.2.6.1). > > However, certain scenarios, such as connecting devices through an APTIV hub, > can lead to timeout errors when the device enumerates as full speed initially > and later switches to high speed during chirp negotiation. > > In such cases, USB analyzer logs reveal that the bus suspends for 5 seconds > due to incorrect chirp parsing and resumes only after two consecutive > timeout errors trigger a hub driver reset. > > Packet(54) Dir(?) Full Speed J(997.100 us) Idle( 2.850 us) > _______| Time Stamp(28 . 105 910 682) > _______|_________________________________________________________________Ch0 > Packet(55) Dir(?) Full Speed J(997.118 us) Idle( 2.850 us) > _______| Time Stamp(28 . 106 910 632) > _______|_________________________________________________________________Ch0 > Packet(56) Dir(?) Full Speed J(399.650 us) Idle(222.582 us) > _______| Time Stamp(28 . 107 910 600) > _______|_________________________________________________________________Ch0 > Packet(57) Dir Chirp J( 23.955 ms) Idle(115.169 ms) > _______| Time Stamp(28 . 108 532 832) > _______|_________________________________________________________________Ch0 > Packet(58) Dir(?) Full Speed J (Suspend)( 5.347 sec) Idle( 5.366 us) > _______| Time Stamp(28 . 247 657 600) > _______|_________________________________________________________________Ch0 > > This 5-second delay in device enumeration is undesirable, particularly in > automotive applications where quick enumeration is crucial > (ideally within 3 seconds). > > The newly introduced quirks provide the flexibility to align with a > 3-second time limit, as required in specific contexts like automotive > applications. > > By reducing the 'set_address' command timeout to 500 ms, the > system can respond more swiftly to errors, initiate rapid recovery, and > ensure efficient device enumeration. This change is vital for scenarios > where rapid smartphone enumeration and screen projection are essential. > To use the quirk, please write "vendor_id:product_id:p" to > /sys/bus/usb/drivers/hub/module/parameter/quirks > > For example, > echo "0x2c48:0x0132:p" > /sys/bus/usb/drivers/hub/module/parameter/quirks" > > Signed-off-by: Hardik Gajjar > --- > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 0a1731a0f0ef..3c03f23bd5d5 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -6817,6 +6817,9 @@ > pause after every control message); > o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra > delay after resetting its port); > + p = USB_QUIRK_SHORT_DEVICE_ADDR_TIMEOUT (Timeout > + of set_address command reducing from > + 5000 ms to 500 ms) As a matter of grammatical style, it would be better to rephrase this as: Reduce timeout of set_address command from 5000 ms to 500 ms Apart from that one little nit, for the usbcore portions of the patch: Reviewed-by: Alan Stern Alan Stern