| Message ID | 20220914120949.747951-6-rf@opensource.cirrus.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | soundwire: Fixes for spurious and missing UNATTACH | expand |
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 */
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 */
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> --- drivers/soundwire/bus.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-)