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>
diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index cb482da..acb8d11 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);