diff options
author | Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> | 2020-01-14 18:08:35 -0600 |
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committer | Vinod Koul <vkoul@kernel.org> | 2020-02-25 15:57:01 +0530 |
commit | 2140b66b5d3ecf6c7c0fa9dc5eebb41855765ace (patch) | |
tree | 81685de05051ea3febde16436dfbace43dfec4de /drivers/soundwire | |
parent | eff346f24ba97c3a7c16261d3157adf61ac8960c (diff) | |
download | linux-2140b66b5d3ecf6c7c0fa9dc5eebb41855765ace.tar.bz2 |
soundwire: bus: fix race condition with probe_complete signaling
The driver probe takes care of basic initialization and is invoked
when a Slave becomes attached, after a match between the Slave DevID
registers and ACPI/DT entries.
The update_status callback is invoked when a Slave state changes,
e.g. when it is assigned a non-zero Device Number and it reports with
an ATTACHED/ALERT state.
The state change detection is usually hardware-based and based on the
SoundWire frame rate (e.g. double-digit microseconds) while the probe
is a pure software operation, which may involve a kernel module
load. In corner cases, it's possible that the state changes before the
probe completes.
This patch suggests the use of wait_for_completion to avoid races on
startup, so that the update_status callback does not rely on invalid
pointers/data structures.
Signed-off-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200115000844.14695-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/soundwire')
-rw-r--r-- | drivers/soundwire/bus.c | 25 | ||||
-rw-r--r-- | drivers/soundwire/bus.h | 1 | ||||
-rw-r--r-- | drivers/soundwire/bus_type.c | 5 | ||||
-rw-r--r-- | drivers/soundwire/slave.c | 2 |
4 files changed, 30 insertions, 3 deletions
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 6106577fb3ed..4980dfd6f3a3 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -970,10 +970,29 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) static int sdw_update_slave_status(struct sdw_slave *slave, enum sdw_slave_status status) { - if (slave->ops && slave->ops->update_status) - return slave->ops->update_status(slave, status); + unsigned long time; - return 0; + if (!slave->probed) { + /* + * the slave status update is typically handled in an + * interrupt thread, which can race with the driver + * probe, e.g. when a module needs to be loaded. + * + * make sure the probe is complete before updating + * status. + */ + time = wait_for_completion_timeout(&slave->probe_complete, + msecs_to_jiffies(DEFAULT_PROBE_TIMEOUT)); + if (!time) { + dev_err(&slave->dev, "Probe not complete, timed out\n"); + return -ETIMEDOUT; + } + } + + if (!slave->ops || !slave->ops->update_status) + return 0; + + return slave->ops->update_status(slave, status); } /** diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h index cb482da914da..acb8d11a4c84 100644 --- a/drivers/soundwire/bus.h +++ b/drivers/soundwire/bus.h @@ -5,6 +5,7 @@ #define __SDW_BUS_H #define DEFAULT_BANK_SWITCH_TIMEOUT 3000 +#define DEFAULT_PROBE_TIMEOUT 2000 #if IS_ENABLED(CONFIG_ACPI) int sdw_acpi_find_slaves(struct sdw_bus *bus); diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c index 4a465f55039f..17f096dd6806 100644 --- a/drivers/soundwire/bus_type.c +++ b/drivers/soundwire/bus_type.c @@ -110,6 +110,11 @@ static int sdw_drv_probe(struct device *dev) slave->bus->clk_stop_timeout = max_t(u32, slave->bus->clk_stop_timeout, slave->prop.clk_stop_timeout); + slave->probed = true; + complete(&slave->probe_complete); + + dev_dbg(dev, "probe complete\n"); + return 0; } diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c index 19919975bb6d..08db0488e02d 100644 --- a/drivers/soundwire/slave.c +++ b/drivers/soundwire/slave.c @@ -47,6 +47,8 @@ static int sdw_slave_add(struct sdw_bus *bus, slave->bus = bus; slave->status = SDW_SLAVE_UNATTACHED; slave->dev_num = 0; + init_completion(&slave->probe_complete); + slave->probed = false; mutex_lock(&bus->bus_lock); list_add_tail(&slave->node, &bus->slaves); |