On 9/14/22 14:09, Richard Fitzgerald wrote:
Only exit sdw_handle_slave_status() right after calling sdw_program_device_num() if it actually programmed an ID into at least one device.
sdw_handle_slave_status() should protect itself against phantom device #0 ATTACHED indications. In that case there is no actual device still on #0. The early exit relies on there being a status change to ATTACHED on the reprogrammed device to trigger another call to sdw_handle_slave_status() which will then handle the status of all peripherals. If no device was actually programmed with an ID there won't be a new ATTACHED indication. This can lead to the status of other peripherals not being handled.
The status passed to sdw_handle_slave_status() is obviously always from a point of time in the past, and may indicate accumulated unhandled events (depending how the bus manager operates). It's possible that a device ID is reprogrammed but the last PING status captured state just before that, when it was still reporting on ID #0. Then sdw_handle_slave_status() is called with this PING info, just before a new PING status is available showing it now on its new ID. So sdw_handle_slave_status() will receive a phantom report of a device on #0, but it will not find one.
Signed-off-by: Richard Fitzgerald rf@opensource.cirrus.com
Nice work, thanks Richard
Reviewed-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com
drivers/soundwire/bus.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 6e569a875a9b..8eded1a55227 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -729,7 +729,7 @@ 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, bool *programmed) { u8 buf[SDW_NUM_DEV_ID_REGISTERS] = {0}; struct sdw_slave *slave, *_s; @@ -739,6 +739,8 @@ static int sdw_program_device_num(struct sdw_bus *bus) int count = 0, ret; u64 addr;
- *programmed = false;
- /* No Slave, so use raw xfer api */ ret = sdw_fill_msg(&msg, NULL, SDW_SCP_DEVID_0, SDW_NUM_DEV_ID_REGISTERS, 0, SDW_MSG_FLAG_READ, buf);
@@ -797,6 +799,8 @@ static int sdw_program_device_num(struct sdw_bus *bus) return ret; }
*programmed = true;break; }@@ -1756,7 +1760,7 @@ int sdw_handle_slave_status(struct sdw_bus *bus, { enum sdw_slave_status prev_status; struct sdw_slave *slave;
- bool attached_initializing;
bool attached_initializing, id_programmed; int i, ret = 0;
/* first check if any Slaves fell off the bus */
@@ -1787,14 +1791,23 @@ 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
* Programming a device number will have side effects,* so we deal with other devices at a later time.* This relies on those devices reporting ATTACHED, which will* trigger another call to this function. This will only* happen if at least one device ID was programmed.* Error returns from sdw_program_device_num() are currently* ignored because there's no useful recovery that can be done.* Returning the error here could result in the current status* of other devices not being handled, because if no device IDs* were programmed there's nothing to guarantee a status change* to trigger another call to this function.
return ret;
sdw_program_device_num(bus, &id_programmed);if (id_programmed)return 0;}
/* Continue to check other slave statuses */