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 B5DC4C4167B for ; Fri, 1 Dec 2023 16:13:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378288AbjLAQNv (ORCPT ); Fri, 1 Dec 2023 11:13:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1378234AbjLAQNu (ORCPT ); Fri, 1 Dec 2023 11:13:50 -0500 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by lindbergh.monkeyblade.net (Postfix) with SMTP id 1B57010F3 for ; Fri, 1 Dec 2023 08:13:54 -0800 (PST) Received: (qmail 291319 invoked by uid 1000); 1 Dec 2023 11:13:53 -0500 Date: Fri, 1 Dec 2023 11:13:53 -0500 From: Alan Stern To: Hardik Gajjar Cc: gregkh@linuxfoundation.org, corbet@lwn.net, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, erosca@de.adit-jv.com, tj@kernel.org, paulmck@kernel.org, Martin.Mueller5@de.bosch.com Subject: Re: [PATCH v3] usb: hub: Add quirk to decrease IN-ep poll interval for Microchip USB491x hub Message-ID: <39f334d2-abe6-4b4d-a48c-b22a907c6ea6@rowland.harvard.edu> References: <20231201144705.97385-1-hgajjar@de.adit-jv.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231201144705.97385-1-hgajjar@de.adit-jv.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 01, 2023 at 03:47:05PM +0100, Hardik Gajjar wrote: > There is a potential delay in notifying Linux USB drivers of downstream > USB bus activity when connecting a high-speed or superSpeed device via the > Microchip USB491x hub. This delay is due to the fixed bInterval value of > 12 in the silicon of the Microchip USB491x hub. > > Microchip requested to ignore the device descriptor and decrease that > value to 9 as it was too late to modify that in silicon. > > This patch speeds up the USB enummeration process that helps to pass > Apple Carplay certifications and improve the User experience when utilizing > the USB device via Microchip Multihost USB491x Hub. > > A new hub quirk HUB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL speeds up > the notification process for Microchip USB491x hub by limiting > the maximum bInterval value to 9. > > Signed-off-by: Hardik Gajjar > --- > changes since version 1: > - Move implementation from config.c and quirk.c to hub.c as this is hub > specific changes. > - Improve commit message. > - Link to v1 - https://lore.kernel.org/all/20231123081948.58776-1-hgajjar@de.adit-jv.com/ > > changes since version 2: > - Call usb_set_interface after updating the bInterval to Tell the HCD about modification > - Link to v2 - https://lore.kernel.org/all/20231130084855.119937-1-hgajjar@de.adit-jv.com/ > --- > drivers/usb/core/hub.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > index b4584a0cd484..b5ac29c5f016 100644 > --- a/drivers/usb/core/hub.c > +++ b/drivers/usb/core/hub.c > @@ -47,12 +47,18 @@ > #define USB_VENDOR_TEXAS_INSTRUMENTS 0x0451 > #define USB_PRODUCT_TUSB8041_USB3 0x8140 > #define USB_PRODUCT_TUSB8041_USB2 0x8142 > +#define USB_VENDOR_MICROCHIP 0x0424 > +#define USB_PRODUCT_USB4913 0x4913 > +#define USB_PRODUCT_USB4914 0x4914 > +#define USB_PRODUCT_USB4915 0x4915 > #define HUB_QUIRK_CHECK_PORT_AUTOSUSPEND 0x01 > #define HUB_QUIRK_DISABLE_AUTOSUSPEND 0x02 > +#define HUB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL 0x08 Why use 0x08 instead of 0x04? Alan Stern