From: Simon Trimmer simont@opensource.cirrus.com

The cadence IP explicitly reports slave status changes with bits for each possible change. The function cdns_update_slave_status() attempts to translate this into the current status of each of the slaves.

However when there are multiple peripherals on a bus any slave that did not have a status change when the work function ran would not have it's status updated - the array is initialised to a value that equates to UNATTACHED and this can cause spurious reports that slaves had dropped off the bus.

In the case where a slave has no status change or has multiple status changes the value from the last PING command is used.

Signed-off-by: Simon Trimmer simont@opensource.cirrus.com Signed-off-by: Richard Fitzgerald rf@opensource.cirrus.com Reviewed-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com --- drivers/soundwire/cadence_master.c | 57 +++++++++++++----------------- 1 file changed, 25 insertions(+), 32 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c index 4fbb19557f5e..245191d22ccd 100644 --- a/drivers/soundwire/cadence_master.c +++ b/drivers/soundwire/cadence_master.c @@ -782,6 +782,7 @@ static int cdns_update_slave_status(struct sdw_cdns *cdns, enum sdw_slave_status status[SDW_MAX_DEVICES + 1]; bool is_slave = false; u32 mask; + u32 val; int i, set_status;

memset(status, 0, sizeof(status)); @@ -789,41 +790,38 @@ static int cdns_update_slave_status(struct sdw_cdns *cdns, for (i = 0; i <= SDW_MAX_DEVICES; i++) { mask = (slave_intstat >> (i * CDNS_MCP_SLAVE_STATUS_NUM)) & CDNS_MCP_SLAVE_STATUS_BITS; - if (!mask) - continue;

- is_slave = true; set_status = 0;

- if (mask & CDNS_MCP_SLAVE_INTSTAT_RESERVED) { - status[i] = SDW_SLAVE_RESERVED; - set_status++; - } - - if (mask & CDNS_MCP_SLAVE_INTSTAT_ATTACHED) { - status[i] = SDW_SLAVE_ATTACHED; - set_status++; - } + if (mask) { + is_slave = true;

- if (mask & CDNS_MCP_SLAVE_INTSTAT_ALERT) { - status[i] = SDW_SLAVE_ALERT; - set_status++; - } + if (mask & CDNS_MCP_SLAVE_INTSTAT_RESERVED) { + status[i] = SDW_SLAVE_RESERVED; + set_status++; + }

- if (mask & CDNS_MCP_SLAVE_INTSTAT_NPRESENT) { - status[i] = SDW_SLAVE_UNATTACHED; - set_status++; - } + if (mask & CDNS_MCP_SLAVE_INTSTAT_ATTACHED) { + status[i] = SDW_SLAVE_ATTACHED; + set_status++; + }

- /* first check if Slave reported multiple status */ - if (set_status > 1) { - u32 val; + if (mask & CDNS_MCP_SLAVE_INTSTAT_ALERT) { + status[i] = SDW_SLAVE_ALERT; + set_status++; + }

- dev_warn_ratelimited(cdns->dev, - "Slave %d reported multiple Status: %d\n", - i, mask); + if (mask & CDNS_MCP_SLAVE_INTSTAT_NPRESENT) { + status[i] = SDW_SLAVE_UNATTACHED; + set_status++; + } + }

- /* check latest status extracted from PING commands */ + /* + * check that there was a single reported Slave status and when + * there is not use the latest status extracted from PING commands + */ + if (set_status != 1) { val = cdns_readl(cdns, CDNS_MCP_SLAVE_STAT); val >>= (i * 2);

@@ -842,11 +840,6 @@ static int cdns_update_slave_status(struct sdw_cdns *cdns, status[i] = SDW_SLAVE_RESERVED; break; } - - dev_warn_ratelimited(cdns->dev, - "Slave %d status updated to %d\n", - i, status[i]); - } }

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 Reviewed-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com --- drivers/soundwire/bus.c | 10 ++++++++++ 1 file changed, 10 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 1cc858b4107d..6e569a875a9b 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -773,6 +773,16 @@ static int sdw_program_device_num(struct sdw_bus *bus) if (sdw_compare_devid(slave, id) == 0) { found = true;

+ /* + * To prevent skipping state-machine stages don't + * program a device until we've seen it UNATTACH. + * Must return here because no other device on #0 + * can be detected until this one has been + * assigned a device ID. + */ + if (slave->status != SDW_SLAVE_UNATTACHED) + return 0; + /* * Assign a new dev_num to this Slave and * not mark it present. It will be marked

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(-)

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 */