From patchwork Thu Jul 15 13:15:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathias Nyman X-Patchwork-Id: 477833 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 2FBBEC07E96 for ; Thu, 15 Jul 2021 13:13:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1114D613BB for ; Thu, 15 Jul 2021 13:13:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237422AbhGONQt (ORCPT ); Thu, 15 Jul 2021 09:16:49 -0400 Received: from mga07.intel.com ([134.134.136.100]:18215 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232518AbhGONQs (ORCPT ); Thu, 15 Jul 2021 09:16:48 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10045"; a="274370844" X-IronPort-AV: E=Sophos;i="5.84,242,1620716400"; d="scan'208";a="274370844" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jul 2021 06:13:54 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.84,242,1620716400"; d="scan'208";a="655738900" Received: from mattu-haswell.fi.intel.com ([10.237.72.170]) by fmsmga005.fm.intel.com with ESMTP; 15 Jul 2021 06:13:52 -0700 From: Mathias Nyman To: Cc: , , Mathias Nyman Subject: [PATCH 1/2] usb: hub: Fix link power management max exit latency (MEL) calculations Date: Thu, 15 Jul 2021 16:15:43 +0300 Message-Id: <20210715131544.1984726-1-mathias.nyman@linux.intel.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Maximum Exit Latency (MEL) value is used by host to know how much in advance it needs to start waking up a U1/U2 suspended link in order to service a periodic transfer in time. Current MEL calculation only includes the time to wake up the path from U1/U2 to U0. This is called tMEL1 in USB 3.1 section C 1.5.2 Total MEL = tMEL1 + tMEL2 +tMEL3 + tMEL4 which should additinally include: - tMEL2 which is the time it takes for PING message to reach device - tMEL3 time for device to process the PING and submit a PING_RESPONSE - tMEL4 time for PING_RESPONSE to traverse back upstream to host. Add the missing tMEL2, tMEL3 and tMEL4 to MEL calculation. Signed-off-by: Mathias Nyman --- drivers/usb/core/hub.c | 52 +++++++++++++++++++++++------------------- 1 file changed, 28 insertions(+), 24 deletions(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index d1efc7141333..a35d0bedafa3 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -48,6 +48,7 @@ #define USB_TP_TRANSMISSION_DELAY 40 /* ns */ #define USB_TP_TRANSMISSION_DELAY_MAX 65535 /* ns */ +#define USB_PING_RESPONSE_TIME 400 /* ns */ /* Protect struct usb_device->state and ->children members * Note: Both are also protected by ->dev.sem, except that ->state can @@ -182,8 +183,9 @@ int usb_device_supports_lpm(struct usb_device *udev) } /* - * Set the Maximum Exit Latency (MEL) for the host to initiate a transition from - * either U1 or U2. + * Set the Maximum Exit Latency (MEL) for the host to wakup up the path from + * U1/U2, send a PING to the device and receive a PING_RESPONSE. + * See USB 3.1 section C.1.5.2 */ static void usb_set_lpm_mel(struct usb_device *udev, struct usb3_lpm_parameters *udev_lpm_params, @@ -193,35 +195,37 @@ static void usb_set_lpm_mel(struct usb_device *udev, unsigned int hub_exit_latency) { unsigned int total_mel; - unsigned int device_mel; - unsigned int hub_mel; /* - * Calculate the time it takes to transition all links from the roothub - * to the parent hub into U0. The parent hub must then decode the - * packet (hub header decode latency) to figure out which port it was - * bound for. - * - * The Hub Header decode latency is expressed in 0.1us intervals (0x1 - * means 0.1us). Multiply that by 100 to get nanoseconds. + * tMEL1. time to transition path from host to device into U0. + * MEL for parent already contains the delay up to parent, so only add + * the exit latency for the last link (pick the slower exit latency), + * and the hub header decode latency. See USB 3.1 section C 2.2.1 + * Store MEL in nanoseconds */ total_mel = hub_lpm_params->mel + - (hub->descriptor->u.ss.bHubHdrDecLat * 100); + max(udev_exit_latency, hub_exit_latency) * 1000 + + hub->descriptor->u.ss.bHubHdrDecLat * 100; /* - * How long will it take to transition the downstream hub's port into - * U0? The greater of either the hub exit latency or the device exit - * latency. - * - * The BOS U1/U2 exit latencies are expressed in 1us intervals. - * Multiply that by 1000 to get nanoseconds. + * tMEL2. Time to submit PING packet. Sum of tTPTransmissionDelay for + * each link + wHubDelay for each hub. Add only for last link. + * tMEL4, the time for PING_RESPONSE to traverse upstream is similar. + * Multiply by 2 to include it as well. */ - device_mel = udev_exit_latency * 1000; - hub_mel = hub_exit_latency * 1000; - if (device_mel > hub_mel) - total_mel += device_mel; - else - total_mel += hub_mel; + total_mel += (__le16_to_cpu(hub->descriptor->u.ss.wHubDelay) + + USB_TP_TRANSMISSION_DELAY) * 2; + + /* + * tMEL3, tPingResponse. Time taken by device to generate PING_RESPONSE + * after receiving PING. Also add 2100ns as stated in USB 3.1 C 1.5.2.4 + * to cover the delay if the PING_RESPONSE is queued behind a Max Packet + * Size DP. + * Note these delays should be added only once for the entire path, so + * add them to the MEL of the device connected to the roothub. + */ + if (!hub->hdev->parent) + total_mel += USB_PING_RESPONSE_TIME + 2100; udev_lpm_params->mel = total_mel; }