From: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com
In configurations with two amplifiers on the same link, the Intel CI reports occasional enumeration/initialization timeouts during suspend-resume stress tests, where one of the two amplifiers becomes UNATTACHED immediately after being enumerated. This problem was reported both with Maxim and Realtek codecs, which pointed initially to a problem with status handling on the Intel side.
The Cadence IP integrated on Intel platforms throws an interrupt when the status changes, and the information is kept with sticky bits until cleared. We initially added more checks to make sure the edge detection did not miss any transition, but that did not improve the results significantly.
With the recent addition of the read_ping_status() callback, we were able to show that the status in sticky bits is shown as UNATTACHED even though the PING frames show the problematic device as ATTACHED. That completely breaks the entire logic where we assumed that a peripheral would always re-attach as device0. The resume timeouts make sense in that in those cases, the enumeration/initialization never happens a second time.
One possible explanation is that this problem typically happens when a bus clash is reported, so it could very well be that the detection is fooled by a transient electrical issue or conflict between two peripherals.
This patch conditionally double-checks the status reported in the sticky bits with the actual PING frame status. If the peripheral reports as attached in PING frames, the early detection based on sticky bits is discarded.
Note that this patch only corrects issues of false positives on the manager side.
If the peripheral lost and regain sync, then it would report as attached on Device0. A peripheral that would not reset its dev_num would not be compliant with the MIPI specification.
BugLink: https://github.com/thesofproject/linux/issues/3638 BugLink: https://github.com/thesofproject/linux/issues/3325 Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Reviewed-by: Rander Wang rander.wang@intel.com Signed-off-by: Bard Liao yung-chuan.liao@linux.intel.com --- Hi Vinod,
You will need the "ASoC/soundwire: log actual PING status on resume issues" series which is applied at ASoC tree before appling this patch.
--- drivers/soundwire/bus.c | 19 +++++++++++++++++++ drivers/soundwire/intel.c | 1 + include/linux/soundwire/sdw.h | 3 +++ 3 files changed, 23 insertions(+)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 2772973eebb1..d0d486f07673 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -1767,6 +1767,25 @@ int sdw_handle_slave_status(struct sdw_bus *bus, slave->status != SDW_SLAVE_UNATTACHED) { dev_warn(&slave->dev, "Slave %d state check1: UNATTACHED, status was %d\n", i, slave->status); + + if (bus->recheck_unattached && bus->ops->read_ping_status) { + u32 ping_status; + + mutex_lock(&bus->msg_lock); + + ping_status = bus->ops->read_ping_status(bus); + + mutex_unlock(&bus->msg_lock); + + ping_status >>= (i * 2); + ping_status &= 0x3; + + if (ping_status != 0) { + dev_warn(&slave->dev, "Slave %d state in PING frame is %d, ignoring earlier detection\n", + i, ping_status); + continue; + } + } sdw_modify_slave_status(slave, SDW_SLAVE_UNATTACHED); } } diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c index 25ec9c272239..0c6e674dbf85 100644 --- a/drivers/soundwire/intel.c +++ b/drivers/soundwire/intel.c @@ -1311,6 +1311,7 @@ static int intel_link_probe(struct auxiliary_device *auxdev,
bus->link_id = auxdev->id; bus->dev_num_ida_min = INTEL_DEV_NUM_IDA_MIN; + bus->recheck_unattached = true;
sdw_cdns_probe(cdns);
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h index a2b31d25ea27..51ac71984260 100644 --- a/include/linux/soundwire/sdw.h +++ b/include/linux/soundwire/sdw.h @@ -892,6 +892,8 @@ struct sdw_master_ops { * @dev_num_ida_min: if set, defines the minimum values for the IDA * used to allocate system-unique device numbers. This value needs to be * identical across all SoundWire bus in the system. + * @recheck_unattached: if set, double-check UNATTACHED status changes + * by reading PING frame status. */ struct sdw_bus { struct device *dev; @@ -917,6 +919,7 @@ struct sdw_bus { bool multi_link; int hw_sync_min_links; int dev_num_ida_min; + bool recheck_unattached; };
int sdw_bus_master_add(struct sdw_bus *bus, struct device *parent,