From patchwork Thu Nov 14 17:53:40 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pierre-Louis Bossart X-Patchwork-Id: 11244095 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2307F17E6 for ; Thu, 14 Nov 2019 17:56:39 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AA1672071B for ; Thu, 14 Nov 2019 17:56:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="YNA9ccC/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA1672071B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id D80A81672; Thu, 14 Nov 2019 18:55:46 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz D80A81672 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1573754196; bh=amrqqRX5wteWEjhOBJjhzJNPzmCqY0Nh2r/8Ag9LLko=; h=From:To:Date:In-Reply-To:References:Cc:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=YNA9ccC/LPIuBnXso1GPXDgnyXmJnhkMmLbt0v9ujgEoZSKAI0CCfq6XBf0uoH3dQ rpGPzs45msFr5m0bjL9ktD+bZZnLktK2yCxjcNZPKPl58e+rdEyp2oIWe86kJloR5e NLJn79hHaogkeax0yhoNPEV34k1kUMS8Fj5bbt1U= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id 8BF62F80104; Thu, 14 Nov 2019 18:54:09 +0100 (CET) X-Original-To: alsa-devel@alsa-project.org Delivered-To: alsa-devel@alsa-project.org Received: by alsa1.perex.cz (Postfix, from userid 50401) id D0D25F800EF; Thu, 14 Nov 2019 18:54:04 +0100 (CET) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on alsa1.perex.cz X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=SPF_HELO_NONE,SPF_NONE, URIBL_BLOCKED autolearn=disabled version=3.4.0 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 9F4A4F800CF for ; Thu, 14 Nov 2019 18:54:00 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 9F4A4F800CF X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Nov 2019 09:53:56 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,304,1569308400"; d="scan'208";a="203132948" Received: from chiahuil-mobl.amr.corp.intel.com (HELO pbossart-mobl3.amr.corp.intel.com) ([10.255.228.77]) by fmsmga008.fm.intel.com with ESMTP; 14 Nov 2019 09:53:54 -0800 From: Pierre-Louis Bossart To: alsa-devel@alsa-project.org Date: Thu, 14 Nov 2019 11:53:40 -0600 Message-Id: <20191114175345.21836-2-pierre-louis.bossart@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191114175345.21836-1-pierre-louis.bossart@linux.intel.com> References: <20191114175345.21836-1-pierre-louis.bossart@linux.intel.com> MIME-Version: 1.0 Cc: Pierre-Louis Bossart , tiwai@suse.de, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Ranjani Sridharan , vkoul@kernel.org, broonie@kernel.org, srinivas.kandagatla@linaro.org, jank@cadence.com, slawomir.blauciak@intel.com, Sanyog Kale , Bard liao , Rander Wang Subject: [alsa-devel] [PATCH v3 1/6] soundwire: sdw_slave: add probe_complete structure and new fields X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" When a Slave device becomes synchronized with the bus, it may report its presence in PING frames, as well as optionally asserting an in-band PREQ signal. The bus driver will detect a new Device0, start the enumeration process and assign it a non-zero device number. The SoundWire enumeration provides an arbitration to deal with multiple Slaves reporting ATTACHED at the same time. The bus driver will also invoke the driver .probe() callback associated with this device. The probe() depends on the Linux device core, which handles the match operations and may result in modules being loaded. Once the non-zero device number is programmed, the Slave will report its new status in PING frames and the Master hardware will typically report this status change with an interrupt. At this point, the .update_status() callback of the codec driver will be invoked (usually from an interrupt thread or workqueue scheduled from the interrupt thread). The first race condition which can happen is between the .probe(), which allocates the resources, and .update_status() where initializations are typically handled. The .probe() is only called once during the initial boot, while .update_status() will be called for every bus hardware reset and if the Slave device loses synchronization (an unlikely event but with non-zero probability). The time difference between the end of the enumeration process and a change of status reported by the hardware may be as small as one SoundWire PING frame. The scheduling of the interrupt thread, which invokes .update_status() is not deterministic, but can be small enough to create a race condition. With a 48 kHz frame rate and ideal scheduling cases, the .probe() may be pre-empted within double-digit microseconds. Since there is no guarantee that the .probe() completes by the time .update_status() is invoked as a result of an interrupt, it's not unusual for the .update_status() to rely on data structures that have not been allocated yet, leading to kernel oopses. This patch adds a probe_complete utility, which is used in the sdw_update_slave_status() routine. The codec driver does not need to do anything and can safely assume all resources are allocated in its update_status() callback. Signed-off-by: Pierre-Louis Bossart --- include/linux/soundwire/sdw.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h index 28745b9ba279..cb1db4a7475d 100644 --- a/include/linux/soundwire/sdw.h +++ b/include/linux/soundwire/sdw.h @@ -547,6 +547,10 @@ struct sdw_slave_ops { * @node: node for bus list * @port_ready: Port ready completion flag for each Slave port * @dev_num: Device Number assigned by Bus + * @probed: boolean tracking driver state + * @probe_complete: completion utility to control potential races + * on startup between driver probe/initialization and SoundWire + * Slave state changes/implementation-defined interrupts */ struct sdw_slave { struct sdw_slave_id id; @@ -561,6 +565,8 @@ struct sdw_slave { struct list_head node; struct completion *port_ready; u16 dev_num; + bool probed; + struct completion probe_complete; }; #define dev_to_sdw_dev(_dev) container_of(_dev, struct sdw_slave, dev)