From patchwork Mon Apr 11 11:38:20 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Linus Walleij X-Patchwork-Id: 608757 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3qk7PS4Hznz9sBM for ; Mon, 11 Apr 2016 21:38:52 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.b=LDNr+zT1; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753969AbcDKLid (ORCPT ); Mon, 11 Apr 2016 07:38:33 -0400 Received: from mail-lf0-f43.google.com ([209.85.215.43]:34747 "EHLO mail-lf0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754090AbcDKLia (ORCPT ); Mon, 11 Apr 2016 07:38:30 -0400 Received: by mail-lf0-f43.google.com with SMTP id j11so152308340lfb.1 for ; Mon, 11 Apr 2016 04:38:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id; bh=JR28aSf5vMODbBbnvoggBZLDDee0PItmFWkgqrA9578=; b=LDNr+zT1bm8EhrXOrW0r1IYM8DYkBDEY8fhE8z0jGtdZW5FcCuRWoploYdsErNn02a hpKjSmfpu+gbMblpJyh5p89MKuH8BsvAyVMib8Hlv5Ub1F6MH63Pi7boNcWZwHetqoRP xQFq9lD8kPJPdU4tdsJeEft97lTTPAR+bCnok= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=JR28aSf5vMODbBbnvoggBZLDDee0PItmFWkgqrA9578=; b=foEtssjzhMH2MVGx0FYhnA6LivD1ui1mRzzJ728neEzPGwo95x/Tcta8dG/ZRitRYO NtjtgHKZg2C/3zOtQfC7HUjEGN/7yP+MCcVxq2mfcUcZl5J6OKDbvfo3DZLIJWy53MGH tXKFk5v1DsizCQdMv3FnUx9b78ONvGixavMEFOlrkWecdpr31vSPmZqBzwQ/YheTkmWC kqVP10ea8Ede2aJCdIA3V80G76xQJdqR0wjEvW8Uv+CjhCriFreQCs37LVXdxNw5Wx8q xLmf7bs99WjUAxxEggM5p0eXeXb+DGcNK34OHSgOP65+0y98C+vipKpZCW/XofEbsu/F TaFw== X-Gm-Message-State: AD7BkJJD797muQOSlqIJWTzNheEFSEZEkDaQxG0AjWTD4vcOnQyKtii/sCcr99J4oNnSQiH2 X-Received: by 10.112.56.43 with SMTP id x11mr8210863lbp.145.1460374708887; Mon, 11 Apr 2016 04:38:28 -0700 (PDT) Received: from localhost.localdomain ([85.235.10.227]) by smtp.gmail.com with ESMTPSA id h8sm4371208lbd.48.2016.04.11.04.38.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Apr 2016 04:38:27 -0700 (PDT) From: Linus Walleij To: Wolfram Sang , linux-i2c@vger.kernel.org Cc: Linus Walleij , Mark Brown , Ulf Hansson , "Rafael J. Wysocki" , linux-pm@vger.kernel.org Subject: [PATCH] i2c: let I2C masters ignore their children for PM Date: Mon, 11 Apr 2016 13:38:20 +0200 Message-Id: <1460374700-23269-1-git-send-email-linus.walleij@linaro.org> X-Mailer: git-send-email 2.4.3 Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org When using a certain I2C device with runtime PM enabled on a certain I2C bus adaper the following happens: struct amba_device *foo \ struct i2c_adapter *bar \ struct i2c_client *baz The AMBA device foo has its device PM struct set to ignore children with pm_suspend_ignore_children(&foo->dev, true). This makes runtime PM work just fine locally in the driver: the fact that devices on the bus are suspended or resumed individually does not affect its operation, and the hardware does not power up unless transferring messages. However this child ignorance property is not inherited into the struct i2c_adapter *bar. On system suspend things will work fine. On system resume the following annoying phenomenon occurs: - In the pm_runtime_force_resume() path of struct i2c_client *baz, pm_runtime_set_active(&baz->dev); is eventually called. - This becomes __pm_runtime_set_status(&baz->dev, RPM_ACTIVE); - __pm_runtime_set_status() detects that RPM state is changed, and checks whether the parent is: not active (RPM_ACTIVE) and not ignoring its children If this happens it concludes something is wrong, because a parent that is not ignoring its children must be active before any children activate. - Since the struct i2c_adapter *bar does not ignore its children, the PM core thinks that it must indeed go online before its children, the check bails out with -EBUSY, i.e. the i2c_client *baz thinks it can't work because it's parent is not online, and it respects its parent. - In the driver the .resume() callback returns -EBUSY from the runtime_force_resume() call as per above. This leaves the device in a suspended state, leading to bad behaviour later when the device is used. The following debug print is made with an extra printg patch but illustrates the problem: [ 17.040832] bh1780 2-0029: parent (i2c-2) is not active parent->power.ignore_children = 0 [ 17.040832] bh1780 2-0029: pm_runtime_force_resume: pm_runtime_set_active() failed (-16) [ 17.040863] dpm_run_callback(): pm_runtime_force_resume+0x0/0x88 returns -16 [ 17.040863] PM: Device 2-0029 failed to resume: error -16 Fix this by letting all struct i2c_adapter:s ignore their children: i2c children have no business doing keeping their parents awake: they are completely autonomous devices that just use their parent to talk, a usecase which must be power managed in the host on a per-message basis. Cc: Wolfram Sang Cc: Mark Brown Cc: Ulf Hansson Cc: Rafael J. Wysocki Cc: linux-pm@vger.kernel.org Signed-off-by: Linus Walleij Reviewed-by: Ulf Hansson --- ChangeLog v1->v2: - Change subject from "let I2C masters inherit suspend child ignorance" to "let I2C masters ignore their children for PM" - Use the big hammer and do the sensible thing: mark all i2c adapters as ignoring their children when it comes to power management. --- drivers/i2c/i2c-core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 0f2f8484e8ec..5e114342dcbc 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -1566,6 +1566,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap) pm_runtime_no_callbacks(&adap->dev); pm_runtime_enable(&adap->dev); + pm_suspend_ignore_children(&adap->dev, true); #ifdef CONFIG_I2C_COMPAT res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev,