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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 4ACA4C433E0 for ; Mon, 15 Feb 2021 21:28:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B43E64DF4 for ; Mon, 15 Feb 2021 21:28:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229718AbhBOV2E (ORCPT ); Mon, 15 Feb 2021 16:28:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229717AbhBOV2D (ORCPT ); Mon, 15 Feb 2021 16:28:03 -0500 Received: from mail-yb1-xb36.google.com (mail-yb1-xb36.google.com [IPv6:2607:f8b0:4864:20::b36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E5356C06178B for ; Mon, 15 Feb 2021 13:27:07 -0800 (PST) Received: by mail-yb1-xb36.google.com with SMTP id p186so8524711ybg.2 for ; Mon, 15 Feb 2021 13:27:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=t3E5HIvJpmCJKKGhV4yDRws8HLa9LQ9/qceNMUiRu8c=; b=bBgXGWTdYcTDa8t6fcMwsRlWYc5Y1TndEDFz/4eUixRrAgdkN6ePgJPXLrrmqIxYLw O5MoN8JfVBRNfEIhRNi/KBC742zudWpRI+9MhLKpaQNk6wWiXhIhRgFrimbPfkANmE2c BraA/rL0wKABCMoJqHk8DujPL3of9VYIU/8liiheFaU4qONbc88zCdUs7n2iYYA3dWD1 v3zMpC38CXHGX/+UhDhge2zo58nLARKKkBmSLiaTeAfVCGuYHTBXLOaQrQYf3LPmfvSd yGTSvYpRXgTYiu7L/tvsRDR+M7ETuPeR+khsiLlhCsCUW+BSb0mBpaF1C5U9NLOGzzx6 qTXA== 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; bh=t3E5HIvJpmCJKKGhV4yDRws8HLa9LQ9/qceNMUiRu8c=; b=bppwPLgSrve1jYVJKj/T9vbC3VYGE9JcxG+CdKbrdxOOnNZOzQctkhkKinNdaCfY/t ZUO9QEddtGOlMrVAHs4y+lf0AvYwX8Mi2+XS/UaXEa8LrPiz4XBU55fkw0VwDGVcqqLU cSzoa9e0sd0HPOdP5xKsVVNMbbEs6VOUzyuN3BeJL1+xSV+mA7qGTUXR/j3YFCnR2z6G Kh5bxQvELghlaunZioQd6kGsU60Wl6pRkBlRbMtjNxTB8VQIvnnTFGDgsZmzPAIMAZ+Q CMRWhKSRacJJruN4exXaO0nDPihl6Jl+64LpeP0CgChY+0qKWyDyB9dzROaqgPAIj0Ib L6hA== X-Gm-Message-State: AOAM530Y291ZfQYy7VyNLVeDNh/m6fUYEQehmYLJLnO59oopLPpStM3V X2LC+oBisCFAKbrmpd12r7BF/q6I6oq5AYo2FHVx/w== X-Google-Smtp-Source: ABdhPJxX0RZwX9HWNB/HlZa/4ApbKsvCwfTglop0LrMflmMdROIaq+FilrrCNr6DVAAhj4RkRzXxMPx0xYtjVuYe/xg= X-Received: by 2002:a05:6902:1025:: with SMTP id x5mr25256350ybt.96.1613424426724; Mon, 15 Feb 2021 13:27:06 -0800 (PST) MIME-Version: 1.0 References: <20210205222644.2357303-1-saravanak@google.com> In-Reply-To: From: Saravana Kannan Date: Mon, 15 Feb 2021 13:26:30 -0800 Message-ID: Subject: Re: [PATCH v4 0/8] Make fw_devlink=on more forgiving To: Geert Uytterhoeven Cc: Jonathan Corbet , Greg Kroah-Hartman , "Rafael J. Wysocki" , Kevin Hilman , Ulf Hansson , Len Brown , Len Brown , Pavel Machek , Michael Turquette , Stephen Boyd , Rob Herring , Frank Rowand , Marc Zyngier , Thomas Gleixner , "open list:DOCUMENTATION" , Linux Kernel Mailing List , Linux PM list , linux-clk , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , ACPI Devel Maling List , Marek Szyprowski , Android Kernel Team , Linux-Renesas Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Mon, Feb 15, 2021 at 4:38 AM Geert Uytterhoeven wrote: > > Hi Saravana, > > On Fri, Feb 12, 2021 at 4:00 AM Saravana Kannan wrote: > > On Thu, Feb 11, 2021 at 5:00 AM Geert Uytterhoeven wrote: > > > - I2C on R-Car Gen3 does not seem to use DMA, according to > > > /sys/kernel/debug/dmaengine/summary: > > > > > > -dma4chan0 | e66d8000.i2c:tx > > > -dma4chan1 | e66d8000.i2c:rx > > > -dma5chan0 | e6510000.i2c:tx > > > > I think I need more context on the problem before I can try to fix it. > > I'm also very unfamiliar with that file. With fw_devlink=permissive, > > I2C was using DMA? If so, the next step is to see if the I2C relative > > probe order with DMA is getting changed and if so, why. > > More detailed log: > > platform e66d8000.i2c: Linked as a consumer to e6150000.clock-controller > platform e66d8000.i2c: Linked as a sync state only consumer to e6055400.gpio > > Why is e66d8000.i2c not linked as a consumer to e6700000.dma-controller? Because fw_devlink.strict=1 is not set and dma/iommu is considered an "optional"/"driver decides" dependency. > platform e6700000.dma-controller: Linked as a consumer to > e6150000.clock-controller Is this the only supplier of dma-controller? > platform e66d8000.i2c: Added to deferred list > platform e6700000.dma-controller: Added to deferred list > > bus: 'platform': driver_probe_device: matched device > e6700000.dma-controller with driver rcar-dmac > bus: 'platform': really_probe: probing driver rcar-dmac with > device e6700000.dma-controller > platform e6700000.dma-controller: Driver rcar-dmac requests probe deferral > > bus: 'platform': driver_probe_device: matched device e66d8000.i2c > with driver i2c-rcar > bus: 'platform': really_probe: probing driver i2c-rcar with device > e66d8000.i2c > > I2C becomes available... > > i2c-rcar e66d8000.i2c: request_channel failed for tx (-517) > [...] > > but DMA is not available yet, so the driver falls back to PIO. > > driver: 'i2c-rcar': driver_bound: bound to device 'e66d8000.i2c' > bus: 'platform': really_probe: bound device e66d8000.i2c to driver i2c-rcar > > platform e6700000.dma-controller: Retrying from deferred list > bus: 'platform': driver_probe_device: matched device > e6700000.dma-controller with driver rcar-dmac > bus: 'platform': really_probe: probing driver rcar-dmac with > device e6700000.dma-controller > platform e6700000.dma-controller: Driver rcar-dmac requests probe deferral > platform e6700000.dma-controller: Added to deferred list > platform e6700000.dma-controller: Retrying from deferred list > bus: 'platform': driver_probe_device: matched device > e6700000.dma-controller with driver rcar-dmac > bus: 'platform': really_probe: probing driver rcar-dmac with > device e6700000.dma-controller > driver: 'rcar-dmac': driver_bound: bound to device 'e6700000.dma-controller' > bus: 'platform': really_probe: bound device > e6700000.dma-controller to driver rcar-dmac > > DMA becomes available. > > Here userspace is entered. /sys/kernel/debug/dmaengine/summary shows > that the I2C controllers do not have DMA channels allocated, as the > kernel has performed no more I2C transfers after DMA became available. > > Using i2cdetect shows that DMA is used, which is good: > > i2c-rcar e66d8000.i2c: got DMA channel for rx > > With permissive devlinks, the clock controller consumers are not added > to the deferred probing list, and probe order is slightly different. > The I2C controllers are still probed before the DMA controllers. > But DMA becomes available a bit earlier, before the probing of the last > I2C slave driver. This seems like a race? I'm guessing it's two different threads probing those two devices? And it just happens to work for "permissive" assuming the boot timing doesn't change? > Hence /sys/kernel/debug/dmaengine/summary shows that > some I2C transfers did use DMA. > > So the real issue is that e66d8000.i2c not linked as a consumer to > e6700000.dma-controller. That's because fw_devlink.strict=1 isn't set. If you need DMA to be treated as a mandatory supplier, you'll need to set the flag. Is fw_devlink=on really breaking anything here? It just seems like "permissive" got lucky with the timing and it could break at any point in the future. Thought? -Saravana