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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 5591DC4338F for ; Sat, 21 Aug 2021 07:04:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EAF761056 for ; Sat, 21 Aug 2021 07:04:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232242AbhHUHEy (ORCPT ); Sat, 21 Aug 2021 03:04:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231738AbhHUHEx (ORCPT ); Sat, 21 Aug 2021 03:04:53 -0400 Received: from mail-wr1-x42d.google.com (mail-wr1-x42d.google.com [IPv6:2a00:1450:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 108F4C061575 for ; Sat, 21 Aug 2021 00:04:14 -0700 (PDT) Received: by mail-wr1-x42d.google.com with SMTP id q10so17437279wro.2 for ; Sat, 21 Aug 2021 00:04:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rtst-co-kr.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=WgM87f7rpLd/jbOLyf9WZP12/bowR6IrwwDEu2GtuV8=; b=Pv336bT6BS8zVUAFL8pWU1CGoQdBEw/yAxLORZT8Cj/Ba0BPBttWUz+vdEQINtnec5 q2RFdHep9cG1R6MfS7RuAsBAUf71QOvvsylwQVXcszxZWZLGdJfao5uT5J80KXdOtlu9 SHtyBk5SWC/eZGBBjo+tV85udJiqv5I8QHTKOfnvsQMkqX7SlRtnfYau5O4uzOrkvo+l rMFJR4MAD1C3+4bzI0SoUQ3gTZd6u6nch6F4B+kxdf2ImkNJD5dIfgb1PX9TFJTZz2vf KbzOGeFnG9Mwqm9PfoEJXDhVxDOelhrZAmwoosSLEOPzfXQGSu5fxkL7R5sg5qkiGjhx WiHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=WgM87f7rpLd/jbOLyf9WZP12/bowR6IrwwDEu2GtuV8=; b=DWm6ZFnhYhfOxcV4ERemR0K91UolrIZyHVR8TH92QC5rCvPkRvObDpmlo+9PVlJ4SL FySGAu7aPeBkwclP864kkNe21oEq0HOxNNfk3uOhxCxcFNxnCKJ1ZaZQ4Xzqkjv8/Wol wGRNwap46qvDFCWCfPgEGGb677XF7UaJbYI/kX1GfQdYOAKC4Hjp5V401jsaTmFVj4Z1 1cdYPRs8HYFHOF9thncFrh6KLi1YjeH0nDdZNfRIAaj/A635ZkXBW2JRX5MF4rRyyToL ybC9yGLT6gZI/tLPNm9FtLr2+vljLZgTgSvQEQeJX6aLo65kmCAQODuw7agjKNaTGDNT sx/w== X-Gm-Message-State: AOAM532kd0i4Z0OBwmBMb9rSF9P9SuLNgUPhe3oxJL0ADTzsAaKZ/9kR yNBu10s1MlqObEk1by248iYqe8xFqpilphb0yKGIxw== X-Google-Smtp-Source: ABdhPJxcQ/ExlMzakQLKVKtgk8fM+2HQQTzsMvU9f1V4BSUasYqP11DQmXznbj5+lLlT6kQekSR6zYmUaeHXoLJb/44= X-Received: by 2002:adf:e7d1:: with SMTP id e17mr2450792wrn.151.1629529452393; Sat, 21 Aug 2021 00:04:12 -0700 (PDT) MIME-Version: 1.0 References: <20210817095313.GA671484@ubuntu> <20210818161752.vu6abfv3e6bfqz23@linutronix.de> <20210819084759.stnmit32vs2be46m@linutronix.de> <20210821050511.GA14810@Peter> In-Reply-To: <20210821050511.GA14810@Peter> From: Jeaho Hwang Date: Sat, 21 Aug 2021 16:04:01 +0900 Message-ID: Subject: Re: [PATCH v2] usb: chipidea: local_irq_save/restore added for hw_ep_prime To: Peter Chen Cc: Sebastian Andrzej Siewior , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , linux-rt-users@vger.kernel.org, Linux team , =?UTF-8?B?67OA66y06rSRKEJ5ZW9uIE1vbyBLd2FuZykv7J6Q64+Z7ZmU7JewKUF1dG9tYXRpb24gUGxhdGZvcm0=?= =?UTF-8?B?7Jew6rWs7YyA?= , =?UTF-8?B?7LWc6riw7ZmNKENob2kgS2kgSG9uZykv7J6Q64+Z7ZmU7JewKUF1dG9tYXRpb24gUGxhdGZvcm3sl7A=?= =?UTF-8?B?6rWs7YyA?= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org 2021=EB=85=84 8=EC=9B=94 21=EC=9D=BC (=ED=86=A0) =EC=98=A4=ED=9B=84 2:05, P= eter Chen =EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1: > > On 21-08-20 14:15:55, Jeaho Hwang wrote: > > 2021=EB=85=84 8=EC=9B=94 19=EC=9D=BC (=EB=AA=A9) =EC=98=A4=ED=9B=84 5:4= 8, Sebastian Andrzej Siewior > > =EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1: > > > > > > On 2021-08-19 08:50:27 [+0900], Jeaho Hwang wrote: > > > > Without RT, udc_irq runs as a forced threaded irq handler, so it ru= ns > > > > without any interruption or preemption. NO similar case is found on > > > > non-RT. > > > > > > I see only a devm_request_irq() so no force-threading here. Booting w= ith > > > threadirqs would not lead to the problem since commit > > > 81e2073c175b8 ("genirq: Disable interrupts for force threaded hand= lers") > > > > > > > I was wrong. udc threaded irq handler allows twd interrupt even on > > non-RT and with threaded irq. > > I believed Chen's comment "The function hw_ep_prime is only called at > > udc_irq which is registered as top-half irq handlers. Why the timer > > interrupt is occurred when hw_ep_prime is executing?". > > Hi Jeaho, > > How could you let udc irq as threaded irq? The chipidea interrupt > is registered using devm_request_irq. > HI Peter. We configured the kernel as "low latency desktop" and added "threadirqs" inside the cmdline parameter. Then udc irq handler runs as a thread and shows no suspicious working. I Hope It will help. Thanks. > > We have additional experiments and got the results like below. RNDIS > > host was Windows. > > > > RT, 1ms delay between first ENDPTSETUPSTAT read and priming : error > > case occurred > > RT, 1ms delay + irq_save : no error case occurred. > > non-RT, threaded irq, 1ms delay : no error case occurred even twd > > fires inside the function execution. > > Again, how do you observe it? > > Peter > > > > > It doesn't seem to be a timing issue. But irq definitely affects > > priming on the RT kernel. Do you RT experts have any idea about the > > causes? > > If isr_tr_complete_handler fails ep priming it calls _ep_set_halt and > > goes an infinite loop in hw_ep_set_halt. It was an actual problem we > > experienced. > > So we protect irqs inside hw_ep_priming not to make error cases and > > also add a timeout inside the hw_ep_set_halt loop for a walkaround. > > The timeout patch is submitted to linux-usb. > > ( https://marc.info/?l=3Dlinux-usb&m=3D162918269024007&w=3D2 ) > > > > We withdrew this patch since we don't know if disabling irq is the > > best solution to solve the problem and udc would work fine with > > hw_ep_set_halt walkaround even though hw_ep_prime fails. > > But we are still trying to find out the cause of this symptom so We'd > > so appreciate it if RT or USB experts share some ideas or ways to > > report somewhere. Xilinx doesn't provide any support without their > > official kernel :( > > > > Thanks for the discussion Sebastian. > > > > Jeaho Hwang. > > > > > =E2=80=A6 > > > > > If this function here is sensitive to timing (say the cpu_relax()= loop > > > > > gets interrupt for 1ms) then it has to be documented as such. > > > > > > > > The controller sets ENDPTSETUPSTAT register if the host sent a setu= p packet. > > > > yes it is a timing problem. I will document that and resubmit again= if > > > > you agree that local_irq_save could help from the timing problem. > > > > > > > > Thanks for the advice. > > > > > > If it is really a timing issue in the function as you describe below > > > then disabling interrupts would help and it is indeed an RT only issu= e. > > > > > > So you read OP_ENDPTSETUPSTAT, it is 0, all good. > > > You write OP_ENDPTPRIME, wait for it to be cleared. > > > Then you read OP_ENDPTSETUPSTAT again and if it is 0, all good. > > > > > > And the TWD interrupt could delay say the second read would read 1 an= d > > > it is invalidated. Which looks odd. > > > However, it is "okay" if the TWD interrupt happens after the second > > > read? Even if the host sends a setup packet, nothing breaks? > > > Do you have numbers on how long irq-off section is here? It seems to > > > depend on how long the HW needs to clear the OP_ENDPTPRIME bits. > > > > > > Sebastian > > > > > > > > -- > > =ED=99=A9=EC=9E=AC=ED=98=B8, Jay Hwang, linux team manager of RTst > > 010-7242-1593 > > -- > > Thanks, > Peter Chen > --=20 =ED=99=A9=EC=9E=AC=ED=98=B8, Jay Hwang, linux team manager of RTst