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=-15.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 ADB80C433F5 for ; Thu, 9 Sep 2021 17:02:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9582A61104 for ; Thu, 9 Sep 2021 17:02:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239995AbhIIREB (ORCPT ); Thu, 9 Sep 2021 13:04:01 -0400 Received: from so254-9.mailgun.net ([198.61.254.9]:51384 "EHLO so254-9.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234524AbhIIREA (ORCPT ); Thu, 9 Sep 2021 13:04:00 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1631206971; h=In-Reply-To: Content-Type: MIME-Version: References: Message-ID: Subject: Cc: To: From: Date: Sender; bh=qrLWpwJqydDyGvQEH1EuVqU9HUIie2BZyQM8A4ufF9w=; b=TKDkBtYnVpnwkpXpSELN7bogc1hI7xvh9+V2iMYSl/DWNE2I51IqdeNOVjJ84ir/aXM0BeM8 +mvpeeUP6TySFw7U9ojTKwBoLHAhIfnzRJRdANZzl7gNrNtIkd8p9YlehNb4wYaUKkVlepx4 Kh02I7HY3b8IdS6D+ci5VyGJ6Bw= X-Mailgun-Sending-Ip: 198.61.254.9 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n05.prod.us-west-2.postgun.com with SMTP id 613a3e32aa8996eab7db370a (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 09 Sep 2021 17:02:42 GMT Sender: jackp=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 3EA46C4360D; Thu, 9 Sep 2021 17:02:42 +0000 (UTC) Received: from jackp-linux.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: jackp) by smtp.codeaurora.org (Postfix) with ESMTPSA id EDEDEC43460; Thu, 9 Sep 2021 17:02:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 smtp.codeaurora.org EDEDEC43460 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=codeaurora.org Date: Thu, 9 Sep 2021 10:02:36 -0700 From: Jack Pham To: Felipe Balbi Cc: Greg Kroah-Hartman , Thinh Nguyen , Wesley Cheng , linux-usb@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH] usb: dwc3: gadget: Skip resizing EP's TX FIFO if already resized Message-ID: <20210909170236.GA20111@jackp-linux.qualcomm.com> References: <20210909083120.15350-1-jackp@codeaurora.org> <87fsueb0ko.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87fsueb0ko.fsf@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi Felipe, On Thu, Sep 09, 2021 at 11:41:38AM +0300, Felipe Balbi wrote: > Jack Pham writes: > > > Some functions may dynamically enable and disable their endpoints > > regularly throughout their operation, particularly when Set Interface > > is employed to switch between Alternate Settings. For instance the > > UAC2 function has its respective endpoints for playback & capture > > associated with AltSetting 1, in which case those endpoints would not > > get enabled until the host activates the AltSetting. And they > > conversely become disabled when the interfaces' AltSetting 0 is > > chosen. > > > > With the DWC3 FIFO resizing algorithm recently added, every > > usb_ep_enable() call results in a call to resize that EP's TXFIFO, > > but if the same endpoint is enabled again and again, this incorrectly > > leads to FIFO RAM allocation exhaustion as the mechanism did not > > account for the possibility that endpoints can be re-enabled many > > times. > > > > Example log splat: > > > > dwc3 a600000.dwc3: Fifosize(3717) > RAM size(3462) ep3in depth:217973127 > > configfs-gadget gadget: u_audio_start_capture:521 Error! > > dwc3 a600000.dwc3: request 000000000be13e18 was not queued to ep3in > > > > This is easily fixed by bailing out of dwc3_gadget_resize_tx_fifos() > > if an endpoint is already resized, avoiding the calculation error > > resulting from accumulating the EP's FIFO depth repeatedly. > > > > Fixes: 9f607a309fbe9 ("usb: dwc3: Resize TX FIFOs to meet EP bursting requirements") > > Signed-off-by: Jack Pham > > --- > > drivers/usb/dwc3/gadget.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c > > index 804b50548163..c647c76d7361 100644 > > --- a/drivers/usb/dwc3/gadget.c > > +++ b/drivers/usb/dwc3/gadget.c > > @@ -747,6 +747,10 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep) > > if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1) > > return 0; > > > > + /* bail if already resized */ > > + if (dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1))) > > + return 0; > > + > > heh, not to say "I told you so", but... > > That being said, your test is not very good. The whole idea for resizing > the FIFOs is that in some applications we only use e.g. 2 endpoints and > there is considerable FIFO space left unused. > > The goal is to use that unused FIFO space to squeeze more throughput out > of the pipe, since it amortizes SW latency. > > This patch is essentially the same as reverting the original commit :-) No, it's not quite the same as nullifying the resizing algorithm. This patch is predicated on a key part of the resizing algorithm where dwc3_gadget_clear_tx_fifos() occurs upon receiving Set_Configuration in ep0.c. Which means that each new connection starts off with a blank slate with all the GTXFIFOSIZ(n) registers cleared. Then each EP gets resized one at a time when usb_ep_enable() is called. The problem this patch is fixing is avoiding *re-resizing*, the idea being that if an EP was already resized once during a session (from Set Configuration until the next reset or disconnect), then it should be good to go even if it gets disabled and re-enabled again. Since we lack any boolean state variable in struct dwc3_ep reflecting whether it had already been resized, re-reading the GTXFIFOSIZ register is the next best equivalent. Note also that this check occurs after the if (!dwc->do_fifo_resize) check so this is applicable only if the entire "tx-fifo-resize" mechanism is enabled. Jack -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project