From patchwork Thu Jul 21 23:12:17 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 9242639 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id C1D5260756 for ; Thu, 21 Jul 2016 23:12:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B19B527C0B for ; Thu, 21 Jul 2016 23:12:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A541A27F90; Thu, 21 Jul 2016 23:12:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0D96627C0B for ; Thu, 21 Jul 2016 23:12:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751411AbcGUXM1 (ORCPT ); Thu, 21 Jul 2016 19:12:27 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:42616 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751211AbcGUXM1 (ORCPT ); Thu, 21 Jul 2016 19:12:27 -0400 Received: from debutante.sirena.org.uk ([2a01:348:6:8808:fab::3] helo=debutante) by mezzanine.sirena.org.uk with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1bQN8e-0005KJ-LC; Thu, 21 Jul 2016 23:12:21 +0000 Received: from broonie by debutante with local (Exim 4.87) (envelope-from ) id 1bQN8b-0000k4-KN; Fri, 22 Jul 2016 00:12:17 +0100 From: Mark Brown To: Rich Felker Cc: linux-spi@vger.kernel.org, Mark Brown Date: Fri, 22 Jul 2016 00:12:17 +0100 Message-Id: <1469142737-2814-1-git-send-email-broonie@kernel.org> X-Mailer: git-send-email 2.8.1 X-SA-Exim-Connect-IP: 2a01:348:6:8808:fab::3 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: [PATCH] spi: Split bus and I/O locking X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The current SPI code attempts to use bus_lock_mutex for two purposes. One is to implement spi_bus_lock() which grants exclusive access to the bus. The other is to serialize access to the physical hardware. This duplicate purpose causes confusion which leads to cases where access is not locked when a caller holds the bus lock mutex. Fix this by splitting out the I/O functionality into a new io_mutex. This means taking both mutexes in the DMA path, replacing the existing mutex with the new I/O one in the message pump (the mutex now always being taken in the message pump) and taking the bus lock mutex in spi_sync(), allowing __spi_sync() to have no mutex handling. While we're at it hoist the mutex further up the message pump before we power up the device so that all power up/down of the block is covered by it and there are no races with in-line pumping of messages. Signed-off-by: Mark Brown --- *Completely* untested, I've not even tried to run this yet - just quickly throwing it out for testing. drivers/spi/spi.c | 38 ++++++++++++++++++-------------------- include/linux/spi/spi.h | 6 +++++- 2 files changed, 23 insertions(+), 21 deletions(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index be96fcd072e4..fd32dcf599a8 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1088,7 +1088,6 @@ EXPORT_SYMBOL_GPL(spi_finalize_current_transfer); * __spi_pump_messages - function which processes spi message queue * @master: master to process queue for * @in_kthread: true if we are in the context of the message pump thread - * @bus_locked: true if the bus mutex is held when calling this function * * This function checks if there is any spi message in the queue that * needs processing and if so call out to the driver to initialize hardware @@ -1098,8 +1097,7 @@ EXPORT_SYMBOL_GPL(spi_finalize_current_transfer); * inside spi_sync(); the queue extraction handling at the top of the * function should deal with this safely. */ -static void __spi_pump_messages(struct spi_master *master, bool in_kthread, - bool bus_locked) +static void __spi_pump_messages(struct spi_master *master, bool in_kthread) { unsigned long flags; bool was_busy = false; @@ -1171,6 +1169,8 @@ static void __spi_pump_messages(struct spi_master *master, bool in_kthread, master->busy = true; spin_unlock_irqrestore(&master->queue_lock, flags); + mutex_lock(&master->io_mutex); + if (!was_busy && master->auto_runtime_pm) { ret = pm_runtime_get_sync(master->dev.parent); if (ret < 0) { @@ -1195,9 +1195,6 @@ static void __spi_pump_messages(struct spi_master *master, bool in_kthread, } } - if (!bus_locked) - mutex_lock(&master->bus_lock_mutex); - trace_spi_message_start(master->cur_msg); if (master->prepare_message) { @@ -1227,8 +1224,7 @@ static void __spi_pump_messages(struct spi_master *master, bool in_kthread, } out: - if (!bus_locked) - mutex_unlock(&master->bus_lock_mutex); + mutex_unlock(&master->io_mutex); /* Prod the scheduler in case transfer_one() was busy waiting */ if (!ret) @@ -1244,7 +1240,7 @@ static void spi_pump_messages(struct kthread_work *work) struct spi_master *master = container_of(work, struct spi_master, pump_messages); - __spi_pump_messages(master, true, master->bus_lock_flag); + __spi_pump_messages(master, true); } static int spi_init_queue(struct spi_master *master) @@ -1917,6 +1913,7 @@ int spi_register_master(struct spi_master *master) spin_lock_init(&master->queue_lock); spin_lock_init(&master->bus_lock_spinlock); mutex_init(&master->bus_lock_mutex); + mutex_init(&master->io_mutex); master->bus_lock_flag = 0; init_completion(&master->xfer_completion); if (!master->max_dma_len) @@ -2800,6 +2797,7 @@ int spi_flash_read(struct spi_device *spi, } mutex_lock(&master->bus_lock_mutex); + mutex_lock(&master->io_mutex); if (master->dma_rx) { rx_dev = master->dma_rx->device->dev; ret = spi_map_buf(master, rx_dev, &msg->rx_sg, @@ -2812,6 +2810,7 @@ int spi_flash_read(struct spi_device *spi, if (msg->cur_msg_mapped) spi_unmap_buf(master, rx_dev, &msg->rx_sg, DMA_FROM_DEVICE); + mutex_unlock(&master->io_mutex); mutex_unlock(&master->bus_lock_mutex); if (master->auto_runtime_pm) @@ -2833,8 +2832,7 @@ static void spi_complete(void *arg) complete(arg); } -static int __spi_sync(struct spi_device *spi, struct spi_message *message, - int bus_locked) +static int __spi_sync(struct spi_device *spi, struct spi_message *message) { DECLARE_COMPLETION_ONSTACK(done); int status; @@ -2852,9 +2850,6 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message, SPI_STATISTICS_INCREMENT_FIELD(&master->statistics, spi_sync); SPI_STATISTICS_INCREMENT_FIELD(&spi->statistics, spi_sync); - if (!bus_locked) - mutex_lock(&master->bus_lock_mutex); - /* If we're not using the legacy transfer method then we will * try to transfer in the calling context so special case. * This code would be less tricky if we could remove the @@ -2872,9 +2867,6 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message, status = spi_async_locked(spi, message); } - if (!bus_locked) - mutex_unlock(&master->bus_lock_mutex); - if (status == 0) { /* Push out the messages in the calling context if we * can. @@ -2884,7 +2876,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message, spi_sync_immediate); SPI_STATISTICS_INCREMENT_FIELD(&spi->statistics, spi_sync_immediate); - __spi_pump_messages(master, false, bus_locked); + __spi_pump_messages(master, false); } wait_for_completion(&done); @@ -2917,7 +2909,13 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message, */ int spi_sync(struct spi_device *spi, struct spi_message *message) { - return __spi_sync(spi, message, spi->master->bus_lock_flag); + int ret; + + mutex_lock(&spi->master->bus_lock_mutex); + ret = __spi_sync(spi, message); + mutex_unlock(&spi->master->bus_lock_mutex); + + return ret; } EXPORT_SYMBOL_GPL(spi_sync); @@ -2939,7 +2937,7 @@ EXPORT_SYMBOL_GPL(spi_sync); */ int spi_sync_locked(struct spi_device *spi, struct spi_message *message) { - return __spi_sync(spi, message, 1); + return __spi_sync(spi, message); } EXPORT_SYMBOL_GPL(spi_sync_locked); diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index ab7215c63873..25d6e83e5afe 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -312,8 +312,9 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv) * @flags: other constraints relevant to this driver * @max_transfer_size: function that returns the max transfer size for * a &spi_device; may be %NULL, so the default %SIZE_MAX will be used. + * @io_mutex: mutex for physical bus access * @bus_lock_spinlock: spinlock for SPI bus locking - * @bus_lock_mutex: mutex for SPI bus locking + * @bus_lock_mutex: mutex for exclusion of multiple callers * @bus_lock_flag: indicates that the SPI bus is locked for exclusive use * @setup: updates the device mode and clocking records used by a * device's SPI controller; protocol code may call this. This @@ -447,6 +448,9 @@ struct spi_master { */ size_t (*max_transfer_size)(struct spi_device *spi); + /* I/O mutex */ + struct mutex io_mutex; + /* lock and mutex for SPI bus locking */ spinlock_t bus_lock_spinlock; struct mutex bus_lock_mutex;