Humm, I am struggling a bit more on this patch. On 8/25/22 14:22, Richard Fitzgerald wrote: > Rearrange sdw_handle_slave_status() so that any peripherals > on device #0 that are given a device ID are reported as > unattached. The ensures that UNATTACH status is not lost. > > Handle unenumerated devices first and update the > sdw_slave_status array to indicate IDs that must have become > UNATTACHED. > > Look for UNATTACHED devices after this so we can pick up > peripherals that were UNATTACHED in the original PING status > and those that were still ATTACHED at the time of the PING but > then reverted to unenumerated and were found by > sdw_program_device_num(). Are those two cases really lost completely? It's a bit surprising, I do recall that we added a recheck on the status, see the 'update_status' label in cdns_update_slave_status_work > As sdw_update_slave_status() is always processing a snapshot of > a PING from some time in the past, it is possible that the status > is changing while sdw_update_slave_status() is running. > > A peripheral could report attached in the PING, but detach and > revert to device #0 and then be found in the loop in > sdw_program_device_num(). Previously the code would not have > updated slave->status to UNATTACHED because there was never a > PING with that status. If the slave->status is not updated to > UNATTACHED the next PING will report it as ATTACHED, but its > slave->status is already ATTACHED so the re-attach will not be > properly handled. The idea of detecting first devices that become unattached - and later deal with device0 when they re-attach - was based on the fact that synchronization takes time. The absolute minimum is 16 frames per the SoundWire spec. I don't see how testing for the status[0] first in sdw_handle_slave_status() helps, the value is taken at the same time as status[1..11]. If you really want to take the last information, we should re-read the status from a new PING frame. > This situations 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 | 39 ++++++++++++++++++++++++++------------- > 1 file changed, 26 insertions(+), 13 deletions(-) > > diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c > index bb8ce26c68b3..1212148ac251 100644 > --- a/drivers/soundwire/bus.c > +++ b/drivers/soundwire/bus.c > @@ -718,7 +718,8 @@ void sdw_extract_slave_id(struct sdw_bus *bus, > } > EXPORT_SYMBOL(sdw_extract_slave_id); > > -static int sdw_program_device_num(struct sdw_bus *bus) > +static int sdw_program_device_num(struct sdw_bus *bus, > + enum sdw_slave_status status[]) > { > u8 buf[SDW_NUM_DEV_ID_REGISTERS] = {0}; > struct sdw_slave *slave, *_s; > @@ -776,6 +777,12 @@ static int sdw_program_device_num(struct sdw_bus *bus) > return ret; > } > > + /* > + * It could have dropped off the bus since the > + * PING response so update the status array. > + */ > + status[slave->dev_num] = SDW_SLAVE_UNATTACHED; > + > break; > } > } > @@ -1735,10 +1742,21 @@ int sdw_handle_slave_status(struct sdw_bus *bus, > { > enum sdw_slave_status prev_status; > struct sdw_slave *slave; > + bool programmed_dev_num = false; > bool attached_initializing; > int i, ret = 0; > > - /* first check if any Slaves fell off the bus */ > + /* Handle any unenumerated peripherals */ > + if (status[0] == SDW_SLAVE_ATTACHED) { > + dev_dbg(bus->dev, "Slave attached, programming device number\n"); > + ret = sdw_program_device_num(bus, status); > + if (ret < 0) > + dev_warn(bus->dev, "Slave attach failed: %d\n", ret); > + > + programmed_dev_num = true; > + } > + > + /* Check if any fell off the bus */ > for (i = 1; i <= SDW_MAX_DEVICES; i++) { > mutex_lock(&bus->bus_lock); > if (test_bit(i, bus->assigned) == false) { > @@ -1764,17 +1782,12 @@ int sdw_handle_slave_status(struct sdw_bus *bus, > } > } > > - if (status[0] == SDW_SLAVE_ATTACHED) { > - dev_dbg(bus->dev, "Slave attached, programming device number\n"); > - ret = sdw_program_device_num(bus); > - if (ret < 0) > - dev_err(bus->dev, "Slave attach failed: %d\n", ret); > - /* > - * programming a device number will have side effects, > - * so we deal with other devices at a later time > - */ > - return ret; > - } > + /* > + * programming a device number will have side effects, > + * so we deal with other devices at a later time > + */ > + if (programmed_dev_num) > + return 0; > > /* Continue to check other slave statuses */ > for (i = 1; i <= SDW_MAX_DEVICES; i++) {