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=-13.2 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,URIBL_BLOCKED,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 91474C433E9 for ; Wed, 17 Feb 2021 23:58:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 590ED64EAD for ; Wed, 17 Feb 2021 23:58:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230315AbhBQX6i (ORCPT ); Wed, 17 Feb 2021 18:58:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230303AbhBQX6g (ORCPT ); Wed, 17 Feb 2021 18:58:36 -0500 Received: from mail-yb1-xb34.google.com (mail-yb1-xb34.google.com [IPv6:2607:f8b0:4864:20::b34]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E943FC061786 for ; Wed, 17 Feb 2021 15:57:55 -0800 (PST) Received: by mail-yb1-xb34.google.com with SMTP id n195so392666ybg.9 for ; Wed, 17 Feb 2021 15:57:55 -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=gyyd+fg6rE1jikDjwjComYSD9NHlv04HXSqrgjKmU18=; b=g74HmmdJSYKVCHRbytSRkHgd4z3jdETXm4uDfSzCa6DrvZZX/JtQKKxBIabrkWOhUx JzLhYIdmK9+4a+TIIIpgQpcTPa10bFzsd5Obcs+85Zd2729d+a79LfumiVXstLdfaFeX 3PmgDObTOtKT2+StqbGtYMqk/V2b7H2RjvrEJZE8xbEFQvimTrlbT1Juz9HtX3utvtrx 2tMaWKn9BEQ2GIPCsLDcVVnRIXv31H00A2I2ET5OzWRD0nJe1PzwB1JZPL3YCssCVygf 7HuR5fDQf9DNuu2M8Ow1OdqHHmgf9NFSWIRYWIqVn9YTIynb5OGRcisVQcnO3WBoRasl 1T+Q== 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=gyyd+fg6rE1jikDjwjComYSD9NHlv04HXSqrgjKmU18=; b=X5aq806Me9ZyGZ/M6TkguKyaPBQxvwf0EEo0GFeGTiN4QDEGwjHgK/ZrV6W0GRF2+9 RkCX55rWkEaGgz1CZaD4b5ZO1Q9zuz6mMXLoMXzC9olmECQUMlmDU9YO7ZIPpb/8kbfk cj4C+N4HrdMLLfHVvWtycL7sEkMxSe4OJu3lW1KuMBPPfb+k9Xi2lk/jo03NgwuvxwY8 N0EOq/m5fa/mf8r+Jk1xfZZKdbpogXl7uZuud+75+sc2Ku9hdbC3IQhEK82oBPGtk0X/ WmXPqsW7/wfF6MKDrya9B4d2tNZNC7R+l5IH17JVL34GeX/wqi22X6p9zek2JRcMvHjx 3sXw== X-Gm-Message-State: AOAM53115eus7/u3vEHySPhRNj54/XeaGk7fSdeqYdijzJsBijoj5Lpd 92jw41DnPXO2H2hfTcIu05OsHk7CSnrJ29+yXj2SNw== X-Google-Smtp-Source: ABdhPJyOSQa4Jj9rh8MYWVVAqAFPqUPnVtB1UzPtZJ/GyByZHitchaJCswelIanrPLQJ+P5TzrwtxVaA8GlnZr7rWrE= X-Received: by 2002:a25:8b8b:: with SMTP id j11mr2655973ybl.310.1613606274746; Wed, 17 Feb 2021 15:57:54 -0800 (PST) MIME-Version: 1.0 References: <20210205222644.2357303-1-saravanak@google.com> In-Reply-To: From: Saravana Kannan Date: Wed, 17 Feb 2021 15:57:18 -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-acpi@vger.kernel.org On Tue, Feb 16, 2021 at 12:31 PM Geert Uytterhoeven wrote: > > Hi Saravana, > > On Tue, Feb 16, 2021 at 7:49 PM Saravana Kannan wrote: > > On Tue, Feb 16, 2021 at 12:05 AM Geert Uytterhoeven > > wrote: > > > On Mon, Feb 15, 2021 at 10:27 PM Saravana Kannan wrote: > > > > On Mon, Feb 15, 2021 at 4:38 AM Geert Uytterhoeven wrote: > > > > > 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. > > > > > > Oh, I thought dma/iommu were considered mandatory initially, > > > but dropped as dependencies in the late boot process? > > > > No, I didn't do that in case the drivers that didn't need the > > IOMMU/DMA were sensitive to probe order. > > > > My goal was for fw_devlink=on to not affect probe order for devices > > that currently don't need to defer probe. But see below... > > > > > > > > > > > > > > platform e6700000.dma-controller: Linked as a consumer to > > > > > e6150000.clock-controller > > > > > > > > Is this the only supplier of dma-controller? > > > > > > No, e6180000.system-controller is also a supplier. > > > > > > > > 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? > > > > > > I don't think there is a race. > > > > Can you explain more please? This below makes it sound like DMA just > > sneaks in at the last minute. > > Yes it does, as the DMAC also has a consumer link to the IOMMU. > If you ignore the consumer link from I2C to DMAC, the I2C device has > less dependencies than the DMAC, so the I2C device, and the > devices on the I2C bus, are probed much earlier than the DMAC. Can you give this a shot? https://lore.kernel.org/lkml/20210217235130.1744843-1-saravanak@google.com/T/#u It should make sure fw_devlink doesn't add a device to the deferred probe list too soon and change the probe ordering unnecessarily. -Saravana