On 29/08/2022 10:44, Richard Fitzgerald wrote:
Don't re-enumerate a peripheral on #0 until we have seen and
handled an UNATTACHED notification for that peripheral.
Without this, it is possible for the UNATTACHED status to be missed
and so the slave->status remains at ATTACHED. If slave->status never
changes to UNATTACHED the child driver will never be notified of the
UNATTACH, and the code in sdw_handle_slave_status() will skip the
second part of enumeration because the slave->status has not changed.
This scenario can happen because PINGs are handled in a workqueue
function which is working from a snapshot of an old PING, and there
is no guarantee when this function will run.
A peripheral could report attached in the PING being handled by
sdw_handle_slave_status(), but has since reverted to device #0 and is
then found in the loop in sdw_program_device_num(). Previously the
code would not have updated slave->status to UNATTACHED because it had
not yet handled a PING where that peripheral had UNATTACHED.
This situation happens fairly frequently with multiple peripherals on
a bus that are intentionally reset (for example after downloading
firmware).
Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
---
drivers/soundwire/bus.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index cb77da84a4f9..a3d3d66b3410 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -766,6 +766,13 @@ static int sdw_program_device_num(struct sdw_bus *bus)
if (sdw_compare_devid(slave, id) == 0) {
found = true;
+ /*
+ * Don't re-enumerate a device until we've seen
+ * it UNATTACH.
+ */
+ if (slave->status != SDW_SLAVE_UNATTACHED)
+ break;
This should return. We're going to keep seeing this peripheral as the
next to be enumerated until we program its device ID.
+
/*
* Assign a new dev_num to this Slave and
* not mark it present. It will be marked
