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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 456E7C43381 for ; Tue, 19 Feb 2019 12:20:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07193217D7 for ; Tue, 19 Feb 2019 12:20:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=nbd.name header.i=@nbd.name header.b="VsRwsTvf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727276AbfBSMUY (ORCPT ); Tue, 19 Feb 2019 07:20:24 -0500 Received: from nbd.name ([46.4.11.11]:46788 "EHLO nbd.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726141AbfBSMUX (ORCPT ); Tue, 19 Feb 2019 07:20:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=JAkZYl750xAbqR/qGFm6EMVVoCkPCDFci13PFkZvWuM=; b=VsRwsTvfwKPC+Hfxf6tLQy1lV6 cTzV+xA8BKYtZnj7JJzn5LP++KSe6vApmPKhJYR033Ej43mGU76z8sHUafYAfYeM22iH6/CYURwUe YtBkooE1jY+SgC4Gcgxi8h/yvunoa7IYbXMAHHIz7kRbmmslEzUtXYVP2YU1MjktsmyM=; Subject: Re: [BUG] mt76x0u: Probing issues on Raspberry Pi 3 B+ To: Stanislaw Gruszka Cc: Stefan Wahren , Lorenzo Bianconi , Alan Stern , Doug Anderson , Minas Harutyunyan , USB list , linux-wireless References: <20190214092530.GA17273@redhat.com> <878a7160-2e91-d057-6d27-c6b9d85f700e@i2se.com> <20190215071226.GA2372@redhat.com> <1411983628.668277.1550315118443@email.ionos.de> <20190216140739.GA2236@redhat.com> <2009016263.528260.1550344627996@email.ionos.de> <20190218135247.GA9602@redhat.com> <0e29e99a-6ed4-40fe-1f38-30f1b5530a16@nbd.name> <20190218150303.GD9602@redhat.com> <20190219104208.GA22999@redhat.com> From: Felix Fietkau Openpgp: preference=signencrypt Autocrypt: addr=nbd@nbd.name; prefer-encrypt=mutual; keydata= mQGiBEah5CcRBADIY7pu4LIv3jBlyQ/2u87iIZGe6f0f8pyB4UjzfJNXhJb8JylYYRzIOSxh ExKsdLCnJqsG1PY1mqTtoG8sONpwsHr2oJ4itjcGHfn5NJSUGTbtbbxLro13tHkGFCoCr4Z5 Pv+XRgiANSpYlIigiMbOkide6wbggQK32tC20QxUIwCg4k6dtV/4kwEeiOUfErq00TVqIiEE AKcUi4taOuh/PQWx/Ujjl/P1LfJXqLKRPa8PwD4j2yjoc9l+7LptSxJThL9KSu6gtXQjcoR2 vCK0OeYJhgO4kYMI78h1TSaxmtImEAnjFPYJYVsxrhay92jisYc7z5R/76AaELfF6RCjjGeP wdalulG+erWju710Bif7E1yjYVWeA/9Wd1lsOmx6uwwYgNqoFtcAunDaMKi9xVQW18FsUusM TdRvTZLBpoUAy+MajAL+R73TwLq3LnKpIcCwftyQXK5pEDKq57OhxJVv1Q8XkA9Dn1SBOjNB l25vJDFAT9ntp9THeDD2fv15yk4EKpWhu4H00/YX8KkhFsrtUs69+vZQwbQcRmVsaXggRmll dGthdSA8bmJkQG5iZC5uYW1lPohgBBMRAgAgBQJGoeQnAhsjBgsJCAcDAgQVAggDBBYCAwEC HgECF4AACgkQ130UHQKnbvXsvgCgjsAIIOsY7xZ8VcSm7NABpi91yTMAniMMmH7FRenEAYMa VrwYTIThkTlQuQINBEah5FQQCACMIep/hTzgPZ9HbCTKm9xN4bZX0JjrqjFem1Nxf3MBM5vN CYGBn8F4sGIzPmLhl4xFeq3k5irVg/YvxSDbQN6NJv8o+tP6zsMeWX2JjtV0P4aDIN1pK2/w VxcicArw0VYdv2ZCarccFBgH2a6GjswqlCqVM3gNIMI8ikzenKcso8YErGGiKYeMEZLwHaxE Y7mTPuOTrWL8uWWRL5mVjhZEVvDez6em/OYvzBwbkhImrryF29e3Po2cfY2n7EKjjr3/141K DHBBdgXlPNfDwROnA5ugjjEBjwkwBQqPpDA7AYPvpHh5vLbZnVGu5CwG7NAsrb2isRmjYoqk wu++3117AAMFB/9S0Sj7qFFQcD4laADVsabTpNNpaV4wAgVTRHKV/kC9luItzwDnUcsZUPdQ f3MueRJ3jIHU0UmRBG3uQftqbZJj3ikhnfvyLmkCNe+/hXhPu9sGvXyi2D4vszICvc1KL4RD aLSrOsROx22eZ26KqcW4ny7+va2FnvjsZgI8h4sDmaLzKczVRIiLITiMpLFEU/VoSv0m1F4B FtRgoiyjFzigWG0MsTdAN6FJzGh4mWWGIlE7o5JraNhnTd+yTUIPtw3ym6l8P+gbvfoZida0 TspgwBWLnXQvP5EDvlZnNaKa/3oBes6z0QdaSOwZCRA3QSLHBwtgUsrT6RxRSweLrcabiEkE GBECAAkFAkah5FQCGwwACgkQ130UHQKnbvW2GgCfTKx80VvCR/PvsUlrvdOLsIgeRGAAn1ee RjMaxwtSdaCKMw3j33ZbsWS4 Message-ID: <58097bb1-d726-c48e-2a40-2e12098dfb15@nbd.name> Date: Tue, 19 Feb 2019 13:19:26 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <20190219104208.GA22999@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On 2019-02-19 11:42, Stanislaw Gruszka wrote: > On Mon, Feb 18, 2019 at 07:52:27PM +0100, Felix Fietkau wrote: >> On 2019-02-18 16:03, Stanislaw Gruszka wrote: >> > On Mon, Feb 18, 2019 at 03:43:26PM +0100, Felix Fietkau wrote: >> >> On 2019-02-18 14:52, Stanislaw Gruszka wrote: >> >> > On Sat, Feb 16, 2019 at 08:17:07PM +0100, Stefan Wahren wrote: >> >> >> this is a misunderstanding. The warning is about memory alignment to 32 bit addresses, not about page alignment. This is a typical ARM restriction. Maybe we need to make sure in mt76 that the DMA buffer needs to be aligned. But it's also possible that the warning isn't the root cause of our problem. >> >> >> >> >> > >> >> > I see, it needs 4 bytes alignment . There is already dwc2 code checks >> >> > that and allocate new buffer if the alignment is not right: >> >> > dwc2_alloc_dma_aligned_buffer(), but it does nothing if urb->sg >> >> > is not NULL. I thought mt76usb already provide aligned buffers, but >> >> > looks it does not for one TX special case, which are PROBE REQUEST >> >> > frames. Other frames are aligned by inserting L2 header pad. One >> >> > solution for this would be just submit urb with NULL sg (same as >> >> > Lorenzo's patches do, but still allocating buffers via buf->sg), >> >> > but I think, you have right, we should provide 4 bytes aligned buffers >> >> > by default as other DMA hardware may require that. I'm attaching yet >> >> > another patch to test, which fix up alignment for PROBE REQUEST frames. >> >> This approach looks completely wrong to me. MMIO based hardware does not >> >> need 4-byte aligned buffers at all, other USB controllers do not need >> >> this either. >> >> As Lorenzo already pointed out, re-aligning the buffer is *very* >> >> expensive, so we should not do this in the driver just to work around >> >> quirks in a particular USB host driver. >> > >> > I decided to this patch because I thought some other USB & MMIO DMA >> > platforms might also require this alignment. But it was never triggered >> > in MMIO because on those mt76 is used in AP mode, hence no PROBE >> > REQUEST frames (and scan can be passive on STA mode). >> mt76 is regularly used and tested in STA and Mesh mode as well. >> No DMA alignment related issues there. > > The question is why we need to do 2 bytes header pad ? Is this because > ieee802.11 header length for mt76 hardware has to be multiple of 4 or > it has to be aligned to 4 bytes? It would be strange if length has > to be fixed to 4 bytes and alignment not. However this could be > needed on some platforms and not on others. Not sure why it was added in the hardware, but the MAC assumes that the header is padded to a multiple of 4 bytes in the buffer after it has been copied to device memory via DMA or USB. Because of that, it has nothing to do with the alignment of the source buffer, so the two should not be mixed up. >> >> The way I see it, we have two choices. >> >> 1. Fix dwc2 to do its alignment quirk for the urb->sg != NULL case >> >> 2. Rely on urb->transfer_buffer and keep urb->sg NULL >> > >> > I agree, if this is only needed for dwc2. Though I would investigate >> > if this is not a bug on other platforms as well. >> >From what I can see, using Lorenzo's patches seems to be the better >> solution, since they avoid these corner cases in dwc2 (and maybe other >> drivers as well). I will apply them and then we'll see if we need to do >> any further improvements later on. > > They work on rpi dwc2, but they do not address root of the problem. > There is clearly something wrong how mt76usb handle SG, what is not > fixed. And adding disable_usb_sg module parameter for hcd's supporting > SG should be red flag. I think we're simply dealing with multiple issues here, only some of which are fixed by Lorenzo's patches. I'm pretty sure it's still wrong for mt76 to try to align its buffers, since the Linux USB API supports non-aligned transfer buffers and it should be up to the controller driver to deal with that. dwc2 tries to do that, but that has limitations which I already pointed out and which are properly dealt with by Lorenzo's patches. Any other issues with sg should be investigated separately, they are probably unrelated to this one. - Felix