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=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,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 4E3A2C072B5 for ; Fri, 24 May 2019 17:56:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 202872133D for ; Fri, 24 May 2019 17:56:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PC0DnxCH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728007AbfEXR42 (ORCPT ); Fri, 24 May 2019 13:56:28 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:45009 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726071AbfEXR42 (ORCPT ); Fri, 24 May 2019 13:56:28 -0400 Received: by mail-pl1-f194.google.com with SMTP id c5so4452446pll.11; Fri, 24 May 2019 10:56:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=+4dUJ/hnokGjsx8/lVgqKqVKEuRSybVsaRBnvdF4Ydg=; b=PC0DnxCHpyrvI07oguIz4W11H2VDPektdbmFePYqnjzMliY0lltRJdJSzJGNLoxp/r RZM/1MDsMz1LfbTV5sYnoUjwkX82g18a8OFj+EiJZJswueh4vKKyiwrSAoD58NrReBiG Zrs6JhXhwwnCO5sHvhbRj2HN6thomEdazjjlPAhWdo67k5rcqiqL8k3/uaUBL8TEr3+B DuFbbcA5dhzncKSiWHjKGGjQzXxjtySena2FWmhyO2ftN8Cg1BZIVinsN3Ne2YpJwIbz 7acpfnI4XCuRg1C/PZJ0R8EVtvDHR+c49+COWujXiJKsn+Hsy+2mGWJu6a/zL3HnXlIv BWxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+4dUJ/hnokGjsx8/lVgqKqVKEuRSybVsaRBnvdF4Ydg=; b=SR0fUTkAGelmj170fwOJqOPqIDcxtoGRboT1uC7qiqUbctOM6zKOscXpBZDZKJRcd9 ufC+S3Cd98xOTGbrZu9LoRNoQbhGoTbjFwFC5Uj1wAAAEMIhVhvJr6gNDmQ/lFo9uuiU aO/iy5H7X8S534s05qXGlXxzDoTrUF1sw01uJNLhRQrGs/6Lnu46Z8XIIHMc8npC76B+ RauLzML4fsaGvKJVxF7P1tOScBM+I7s/9mXqKsZskFQV2E+XGaUiZH3UDhOFXQovEQSk UJirmUEH0W/jpTDkWsX3AapPkmc2kO5eps8N1T0bUwPKkkHGUoyi/TEkD289MChXwviJ uqxg== X-Gm-Message-State: APjAAAUBwdt/kbiXCjmsAHr/jksDoDJ7DHlkzNzoDIvl4+JO+IF0vRc5 207HxcNfFIzzNg9lXOyoKvc= X-Google-Smtp-Source: APXvYqwzVVKjKnOJmUq2+WW5KCVQvlDb85InX65Q39KvGOBxb4ZTvqsmrD/jrcKi/v0YIbrwiVPJLw== X-Received: by 2002:a17:902:f081:: with SMTP id go1mr60870708plb.211.1558720587159; Fri, 24 May 2019 10:56:27 -0700 (PDT) Received: from [192.168.1.70] (c-24-6-192-50.hsd1.ca.comcast.net. [24.6.192.50]) by smtp.gmail.com with ESMTPSA id f2sm2631944pgs.83.2019.05.24.10.56.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 24 May 2019 10:56:26 -0700 (PDT) Subject: Re: [PATCH v1 1/5] of/platform: Speed up of_find_device_by_node() To: Saravana Kannan , Rob Herring , Mark Rutland , Greg Kroah-Hartman , "Rafael J. Wysocki" Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com References: <20190524010117.225219-1-saravanak@google.com> <20190524010117.225219-2-saravanak@google.com> From: Frank Rowand Message-ID: <6f4ca588-106f-93d1-8579-9e8d32c8031d@gmail.com> Date: Fri, 24 May 2019 10:56:25 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190524010117.225219-2-saravanak@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sarvana, I'm not reviewing patches 1-5 in any detail, given my reply to patch 0. But I had already skimmed through this patch before I received the email for patch 0, so I want to make one generic comment below, to give some feedback as you continue thinking through possible implementations to solve the underlying problems. On 5/23/19 6:01 PM, Saravana Kannan wrote: > Add a pointer from device tree node to the device created from it. > This allows us to find the device corresponding to a device tree node > without having to loop through all the platform devices. > > However, fallback to looping through the platform devices to handle > any devices that might set their own of_node. > > Signed-off-by: Saravana Kannan > --- > drivers/of/platform.c | 20 +++++++++++++++++++- > include/linux/of.h | 3 +++ > 2 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index 04ad312fd85b..1115a8d80a33 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -42,6 +42,8 @@ static int of_dev_node_match(struct device *dev, void *data) > return dev->of_node == data; > } > > +static DEFINE_SPINLOCK(of_dev_lock); > + > /** > * of_find_device_by_node - Find the platform_device associated with a node > * @np: Pointer to device tree node > @@ -55,7 +57,18 @@ struct platform_device *of_find_device_by_node(struct device_node *np) > { > struct device *dev; > > - dev = bus_find_device(&platform_bus_type, NULL, np, of_dev_node_match); > + /* > + * Spinlock needed to make sure np->dev doesn't get freed between NULL > + * check inside and kref count increment inside get_device(). This is > + * achieved by grabbing the spinlock before setting np->dev = NULL in > + * of_platform_device_destroy(). > + */ > + spin_lock(&of_dev_lock); > + dev = get_device(np->dev); > + spin_unlock(&of_dev_lock); > + if (!dev) > + dev = bus_find_device(&platform_bus_type, NULL, np, > + of_dev_node_match); > return dev ? to_platform_device(dev) : NULL; > } > EXPORT_SYMBOL(of_find_device_by_node); > @@ -196,6 +209,7 @@ static struct platform_device *of_platform_device_create_pdata( > platform_device_put(dev); > goto err_clear_flag; > } > + np->dev = &dev->dev; > > return dev; > > @@ -556,6 +570,10 @@ int of_platform_device_destroy(struct device *dev, void *data) > if (of_node_check_flag(dev->of_node, OF_POPULATED_BUS)) > device_for_each_child(dev, NULL, of_platform_device_destroy); > > + /* Spinlock is needed for of_find_device_by_node() to work */ > + spin_lock(&of_dev_lock); > + dev->of_node->dev = NULL; > + spin_unlock(&of_dev_lock); > of_node_clear_flag(dev->of_node, OF_POPULATED); > of_node_clear_flag(dev->of_node, OF_POPULATED_BUS); > > diff --git a/include/linux/of.h b/include/linux/of.h > index 0cf857012f11..f2b4912cbca1 100644 > --- a/include/linux/of.h > +++ b/include/linux/of.h > @@ -48,6 +48,8 @@ struct property { > struct of_irq_controller; > #endif > > +struct device; > + > struct device_node { > const char *name; > phandle phandle; > @@ -68,6 +70,7 @@ struct device_node { > unsigned int unique_id; > struct of_irq_controller *irq_trans; > #endif > + struct device *dev; /* Device created from this node */ We have actively been working on shrinking the size of struct device_node, as part of reducing the devicetree memory usage. As such, we need strong justification for adding anything to this struct. For example, proof that there is a performance problem that can only be solved by increasing the memory usage. -Frank > }; > > #define MAX_PHANDLE_ARGS 16 >