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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E7EFBC433E1 for ; Wed, 24 Jun 2020 06:45:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC7202088E for ; Wed, 24 Jun 2020 06:45:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="vMBeoFBR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389370AbgFXGpo (ORCPT ); Wed, 24 Jun 2020 02:45:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389352AbgFXGpn (ORCPT ); Wed, 24 Jun 2020 02:45:43 -0400 Received: from mail-wm1-x343.google.com (mail-wm1-x343.google.com [IPv6:2a00:1450:4864:20::343]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82D66C061573 for ; Tue, 23 Jun 2020 23:45:42 -0700 (PDT) Received: by mail-wm1-x343.google.com with SMTP id 22so1231090wmg.1 for ; Tue, 23 Jun 2020 23:45:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=92ct+kIyuYCkffCnaII7e190oKIVCgMIRLBRHDA+hrQ=; b=vMBeoFBR6gWv1XCSeTiSfq4tCcSz6ogFdWuTufhhEEp+YjMHBGUPqKmSHaviBuZMzi jJOmcl8gsMyNsctNAEYmqZD8ara+sb6s9sKlGL+AS3XZlxZGcbKFDg+TxZWu35DDTghi p45RtWBLtPn5Fm2YVLfxcwi8+uRptoq4dghIgqr2Ze3PDzozh3pE1pNbyfC6dfeDTrIq l1Z0odWvxsFi9ZULzqIhf30Gqb5mwhrpmXjOZDPwIFTGGsBGl5osmP4XDaCl3Z0LirID 0TwpDNaxsfwOyKZixZoSN9iCtFiOCJ8q7utyir8piieszXTmAqHtqwjjgVW1u3r1Saiw hLug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=92ct+kIyuYCkffCnaII7e190oKIVCgMIRLBRHDA+hrQ=; b=HF9ytNSGUgPsEl6YyqcDyCqxlOg2f4R5ZqHkUTC0IWYGyrKCJ5qn03uYuWBTKzMmRk Yqwq63wpi/PK67OW+UDKqqaNGBPrvAgn4jPHOBcgnblfCpA0h1Dw0D9x2lKtt0h6YdHF DeSo86MvIIdDr/gm2ZpVOlXqxIc78mNWeLYT5DKK1PMeYw+ajxriptA3FNhJWpHvyCfk XQENehciLtxdSbdA79u0k56ACDCQkyarFAPuVSfbnscRSBFmmAnLj+rYlNVIiiGceunv z/ftYtlqf9bTPWhNZmLwRxFA8DtBY4A4Za6j22UlwquJ300+QaIYdD9uhLTapPaw3XJ2 Kjzg== X-Gm-Message-State: AOAM533HLvjbPjqdkqgfX2GGBXZBIn9RPd++yXD82JYdLhEcxD6bb7D7 1/5ORqD6VGXNmJvyDUgHJ1Oi/Q== X-Google-Smtp-Source: ABdhPJyVDUfjm/E/allflF2ZvSZxow7JcquGxPsnUrNFqdBmD70tuJE9qiLNwz0mWV2sr/rUv8+dfg== X-Received: by 2002:a1c:1b0d:: with SMTP id b13mr7401130wmb.169.1592981141078; Tue, 23 Jun 2020 23:45:41 -0700 (PDT) Received: from dell ([2.27.35.144]) by smtp.gmail.com with ESMTPSA id u23sm11771941wru.94.2020.06.23.23.45.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2020 23:45:40 -0700 (PDT) Date: Wed, 24 Jun 2020 07:45:38 +0100 From: Lee Jones To: Frank Rowand Cc: andy.shevchenko@gmail.com, michael@walle.cc, robh+dt@kernel.org, broonie@kernel.org, devicetree@vger.kernel.org, linus.walleij@linaro.org, linux@roeck-us.net, andriy.shevchenko@linux.intel.com, robin.murphy@arm.com, gregkh@linuxfoundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes Message-ID: <20200624064538.GD954398@dell> References: <20200611191002.2256570-1-lee.jones@linaro.org> <2a25af37-a9b8-e4f3-6092-06c1c907dc9f@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2a25af37-a9b8-e4f3-6092-06c1c907dc9f@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 23 Jun 2020, Frank Rowand wrote: > On 2020-06-11 14:10, Lee Jones wrote: > > Currently, when a child platform device (sometimes referred to as a > > sub-device) is registered via the Multi-Functional Device (MFD) API, > > the framework attempts to match the newly registered platform device > > with its associated Device Tree (OF) node. Until now, the device has > > been allocated the first node found with an identical OF compatible > > string. Unfortunately, if there are, say for example '3' devices > > which are to be handled by the same driver and therefore have the same > > compatible string, each of them will be allocated a pointer to the > > *first* node. > > > > An example Device Tree entry might look like this: > > > > mfd_of_test { > > compatible = "mfd,of-test-parent"; > > #address-cells = <0x02>; > > #size-cells = <0x02>; > > > > child@aaaaaaaaaaaaaaaa { > > compatible = "mfd,of-test-child"; > > reg = <0xaaaaaaaa 0xaaaaaaaa 0 0x11>, > > <0xbbbbbbbb 0xbbbbbbbb 0 0x22>; > > }; > > > > child@cccccccc { > > compatible = "mfd,of-test-child"; > > reg = <0x00000000 0xcccccccc 0 0x33>; > > }; > > > > child@dddddddd00000000 { > > compatible = "mfd,of-test-child"; > > reg = <0xdddddddd 0x00000000 0 0x44>; > > }; > > }; > > > > When used with example sub-device registration like this: > > > > static const struct mfd_cell mfd_of_test_cell[] = { > > OF_MFD_CELL("mfd-of-test-child", NULL, NULL, 0, 0, "mfd,of-test-child"), > > OF_MFD_CELL("mfd-of-test-child", NULL, NULL, 0, 1, "mfd,of-test-child"), > > OF_MFD_CELL("mfd-of-test-child", NULL, NULL, 0, 2, "mfd,of-test-child") > > }; > > > > ... the current implementation will result in all devices being allocated > > the first OF node found containing a matching compatible string: > > > > [0.712511] mfd-of-test-child mfd-of-test-child.0: Probing platform device: 0 > > [0.712710] mfd-of-test-child mfd-of-test-child.0: Using OF node: child@aaaaaaaaaaaaaaaa > > [0.713033] mfd-of-test-child mfd-of-test-child.1: Probing platform device: 1 > > [0.713381] mfd-of-test-child mfd-of-test-child.1: Using OF node: child@aaaaaaaaaaaaaaaa > > [0.713691] mfd-of-test-child mfd-of-test-child.2: Probing platform device: 2 > > [0.713889] mfd-of-test-child mfd-of-test-child.2: Using OF node: child@aaaaaaaaaaaaaaaa > > > > After this patch each device will be allocated a unique OF node: > > > > [0.712511] mfd-of-test-child mfd-of-test-child.0: Probing platform device: 0 > > [0.712710] mfd-of-test-child mfd-of-test-child.0: Using OF node: child@aaaaaaaaaaaaaaaa > > [0.713033] mfd-of-test-child mfd-of-test-child.1: Probing platform device: 1 > > [0.713381] mfd-of-test-child mfd-of-test-child.1: Using OF node: child@cccccccc > > [0.713691] mfd-of-test-child mfd-of-test-child.2: Probing platform device: 2 > > [0.713889] mfd-of-test-child mfd-of-test-child.2: Using OF node: child@dddddddd00000000 > > > > Which is fine if all OF nodes are identical. However if we wish to > > apply an attribute to particular device, we really need to ensure the > > correct OF node will be associated with the device containing the > > correct address. We accomplish this by matching the device's address > > expressed in DT with one provided during sub-device registration. > > Like this: > > > > static const struct mfd_cell mfd_of_test_cell[] = { > > OF_MFD_CELL_REG("mfd-of-test-child", NULL, NULL, 0, 1, "mfd,of-test-child", 0xdddddddd00000000), > > OF_MFD_CELL_REG("mfd-of-test-child", NULL, NULL, 0, 2, "mfd,of-test-child", 0xaaaaaaaaaaaaaaaa), > > OF_MFD_CELL_REG("mfd-of-test-child", NULL, NULL, 0, 3, "mfd,of-test-child", 0x00000000cccccccc) > > }; > > > > This will ensure a specific device (designated here using the > > platform_ids; 1, 2 and 3) is matched with a particular OF node: > > > > [0.712511] mfd-of-test-child mfd-of-test-child.0: Probing platform device: 0 > > [0.712710] mfd-of-test-child mfd-of-test-child.0: Using OF node: child@dddddddd00000000 > > [0.713033] mfd-of-test-child mfd-of-test-child.1: Probing platform device: 1 > > [0.713381] mfd-of-test-child mfd-of-test-child.1: Using OF node: child@aaaaaaaaaaaaaaaa > > [0.713691] mfd-of-test-child mfd-of-test-child.2: Probing platform device: 2 > > [0.713889] mfd-of-test-child mfd-of-test-child.2: Using OF node: child@cccccccc > > > > This implementation is still not infallible, hence the mention of > > "best effort" in the commit subject. Since we have not *insisted* on > > the existence of 'reg' properties (in some scenarios they just do not > > make sense) and no device currently uses the new 'of_reg' attribute, > > we have to make an on-the-fly judgement call whether to associate the > > OF node anyway. Which we do in cases where parent drivers haven't > > specified a particular OF node to match to. So there is a *slight* > > possibility of the following result (note: the implementation here is > > convoluted, but it shows you one means by which this process can > > still break): > > > > /* > > * First entry will match to the first OF node with matching compatible > > * Second will fail, since the first took its OF node and is no longer available > > * Third will succeed > > */ > > static const struct mfd_cell mfd_of_test_cell[] = { > > OF_MFD_CELL("mfd-of-test-child", NULL, NULL, 0, 1, "mfd,of-test-child"), > > OF_MFD_CELL_REG("mfd-of-test-child", NULL, NULL, 0, 2, "mfd,of-test-child", 0xaaaaaaaaaaaaaaaa), > > OF_MFD_CELL_REG("mfd-of-test-child", NULL, NULL, 0, 3, "mfd,of-test-child", 0x00000000cccccccc) > > }; > > > > The result: > > > > [0.753869] mfd-of-test-parent mfd_of_test: Registering 3 devices > > [0.756597] mfd-of-test-child: Failed to locate of_node [id: 2] > > [0.759999] mfd-of-test-child mfd-of-test-child.1: Probing platform device: 1 > > [0.760314] mfd-of-test-child mfd-of-test-child.1: Using OF node: child@aaaaaaaaaaaaaaaa > > [0.760908] mfd-of-test-child mfd-of-test-child.2: Probing platform device: 2 > > [0.761183] mfd-of-test-child mfd-of-test-child.2: No OF node associated with this device > > [0.761621] mfd-of-test-child mfd-of-test-child.3: Probing platform device: 3 > > [0.761899] mfd-of-test-child mfd-of-test-child.3: Using OF node: child@cccccccc > > > > We could code around this with some pre-parsing semantics, but the > > added complexity required to cover each and every corner-case is not > > justified. Merely patching the current failing (via this patch) is > > already working with some pretty small corner-cases. Other issues > > should be patched in the parent drivers which can be achieved simply > > by implementing OF_MFD_CELL_REG(). > > > > Signed-off-by: Lee Jones > > --- > > > > Changelog: > > > > v1 => v2: > > * Simply return -EAGAIN if node is already in use > > * Allow for valid of_reg=0 by introducing use_of_reg boolean flag > > * Split helpers out into separate patch > > > > drivers/mfd/mfd-core.c | 99 +++++++++++++++++++++++++++++++++++----- > > include/linux/mfd/core.h | 10 ++++ > > 2 files changed, 97 insertions(+), 12 deletions(-) [...] > > diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h > > index d01d1299e49dc..a148b907bb7f1 100644 > > --- a/include/linux/mfd/core.h > > +++ b/include/linux/mfd/core.h > > @@ -78,6 +78,16 @@ struct mfd_cell { > > */ > > const char *of_compatible; > > > > + /* > > + * Address as defined in Device Tree. Used to compement 'of_compatible' > > + * (above) when matching OF nodes with devices that have identical > > + * compatible strings > > + */ > > Instead of the above comment, suggest something like instead (I have not properly > line wrapped, to make it easier to see the difference): > > > + /* > > + * Address as defined in Device Tree mfd child node "reg" property. Used in combination with 'of_compatible' > > + * (above) when matching OF nodes with devices that have identical > > + * compatible strings > > + */ I'll split the difference and make it more clear, thanks. -- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog