| Message ID | 20220829094458.1169504-2-rf@opensource.cirrus.com |
|---|---|
| State | New |
| Headers | show |
| Series | soundwire: bus: Fix for missing UNATTACH when re-enumerating | expand |
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@opensource.cirrus.com> > --- > 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
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; + /* * Assign a new dev_num to this Slave and * not mark it present. It will be marked
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@opensource.cirrus.com> --- drivers/soundwire/bus.c | 7 +++++++ 1 file changed, 7 insertions(+)