From: Mark Brown broonie@kernel.org
[ Upstream commit 6098475d4cb48d821bdf453c61118c56e26294f0 ]
Currently we have a global spi_add_lock which we take when adding new devices so that we can check that we're not trying to reuse a chip select that's already controlled. This means that if the SPI device is itself a SPI controller and triggers the instantiation of further SPI devices we trigger a deadlock as we try to register and instantiate those devices while in the process of doing so for the parent controller and hence already holding the global spi_add_lock. Since we only care about concurrency within a single SPI bus move the lock to be per controller, avoiding the deadlock.
This can be easily triggered in the case of spi-mux.
Reported-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spi.c | 17 ++++++----------- include/linux/spi/spi.h | 3 +++ 2 files changed, 9 insertions(+), 11 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index f95f7666cb5b..2c342bded058 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -480,12 +480,6 @@ static LIST_HEAD(spi_controller_list); */ static DEFINE_MUTEX(board_lock);
-/* - * Prevents addition of devices with same chip select and - * addition of devices below an unregistering controller. - */ -static DEFINE_MUTEX(spi_add_lock); - /** * spi_alloc_device - Allocate a new SPI device * @ctlr: Controller to which device is connected @@ -638,9 +632,9 @@ int spi_add_device(struct spi_device *spi) * chipselect **BEFORE** we call setup(), else we'll trash * its configuration. Lock against concurrent add() calls. */ - mutex_lock(&spi_add_lock); + mutex_lock(&ctlr->add_lock); status = __spi_add_device(spi); - mutex_unlock(&spi_add_lock); + mutex_unlock(&ctlr->add_lock); return status; } EXPORT_SYMBOL_GPL(spi_add_device); @@ -660,7 +654,7 @@ static int spi_add_device_locked(struct spi_device *spi) /* Set the bus ID string */ spi_dev_set_name(spi);
- WARN_ON(!mutex_is_locked(&spi_add_lock)); + WARN_ON(!mutex_is_locked(&ctlr->add_lock)); return __spi_add_device(spi); }
@@ -2832,6 +2826,7 @@ int spi_register_controller(struct spi_controller *ctlr) spin_lock_init(&ctlr->bus_lock_spinlock); mutex_init(&ctlr->bus_lock_mutex); mutex_init(&ctlr->io_mutex); + mutex_init(&ctlr->add_lock); ctlr->bus_lock_flag = 0; init_completion(&ctlr->xfer_completion); if (!ctlr->max_dma_len) @@ -2968,7 +2963,7 @@ void spi_unregister_controller(struct spi_controller *ctlr)
/* Prevent addition of new devices, unregister existing ones */ if (IS_ENABLED(CONFIG_SPI_DYNAMIC)) - mutex_lock(&spi_add_lock); + mutex_lock(&ctlr->add_lock);
device_for_each_child(&ctlr->dev, NULL, __unregister);
@@ -2999,7 +2994,7 @@ void spi_unregister_controller(struct spi_controller *ctlr) mutex_unlock(&board_lock);
if (IS_ENABLED(CONFIG_SPI_DYNAMIC)) - mutex_unlock(&spi_add_lock); + mutex_unlock(&ctlr->add_lock); } EXPORT_SYMBOL_GPL(spi_unregister_controller);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 97b8d12b5f2b..5d80c6fd2a22 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -527,6 +527,9 @@ struct spi_controller { /* I/O mutex */ struct mutex io_mutex;
+ /* Used to avoid adding the same CS twice */ + struct mutex add_lock; + /* lock and mutex for SPI bus locking */ spinlock_t bus_lock_spinlock; struct mutex bus_lock_mutex;