[PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

[PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

[Richard Fitzgerald]

The bus and cadence code has several bugs that cause UNATTACH notifications
to either be sent spuriously or to be missed.

These can be seen occasionally with a single peripheral on the bus, but are
much more frequent with multiple peripherals, where several peripherals
could change state and report in consecutive PINGs.

The root of all of these bugs seems to be a code design flaw that assumed
every PING status change would be handled separately. However, PINGs are
handled by a workqueue function and there is no guarantee when that function
will be scheduled to run or how much CPU time it will receive. PINGs will
continue while the work function is handling a snapshot of a previous PING
so the code must take account that (a) status could change during the
work function and (b) there can be a backlog of changes before the IRQ work
function runs again.

Tested with 4 peripherals on 1 bus, and 8 peripherals on 2 buses.

CHANGES SINCE V3:
Fixed minor comment typo in patch #4.

Richard Fitzgerald (4):
  soundwire: bus: Don't lose unattach notifications
  soundwire: bus: Don't re-enumerate before status is UNATTACHED
  soundwire: cadence: Fix lost ATTACHED interrupts when enumerating
  soundwire: bus: Don't exit early if no device IDs were programmed

Simon Trimmer (1):
  soundwire: cadence: fix updating slave status when a bus has multiple
    peripherals

 drivers/soundwire/bus.c            | 44 +++++++++++++---
 drivers/soundwire/cadence_master.c | 80 ++++++++++++++++--------------
 2 files changed, 80 insertions(+), 44 deletions(-)

-- 
2.30.2

[PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

[Richard Fitzgerald]

The bus and cadence code has several bugs that cause UNATTACH notifications
to either be sent spuriously or to be missed.

These can be seen occasionally with a single peripheral on the bus, but are
much more frequent with multiple peripherals, where several peripherals
could change state and report in consecutive PINGs.

The root of all of these bugs seems to be a code design flaw that assumed
every PING status change would be handled separately. However, PINGs are
handled by a workqueue function and there is no guarantee when that function
will be scheduled to run or how much CPU time it will receive. PINGs will
continue while the work function is handling a snapshot of a previous PING
so the code must take account that (a) status could change during the
work function and (b) there can be a backlog of changes before the IRQ work
function runs again.

Tested with 4 peripherals on 1 bus, and 8 peripherals on 2 buses.

CHANGES SINCE V3:
Fixed minor comment typo in patch #4.

Richard Fitzgerald (4):
  soundwire: bus: Don't lose unattach notifications
  soundwire: bus: Don't re-enumerate before status is UNATTACHED
  soundwire: cadence: Fix lost ATTACHED interrupts when enumerating
  soundwire: bus: Don't exit early if no device IDs were programmed

Simon Trimmer (1):
  soundwire: cadence: fix updating slave status when a bus has multiple
    peripherals

 drivers/soundwire/bus.c            | 44 +++++++++++++---
 drivers/soundwire/cadence_master.c | 80 ++++++++++++++++--------------
 2 files changed, 80 insertions(+), 44 deletions(-)

-- 
2.30.2

[PATCH v4 1/5] soundwire: cadence: fix updating slave status when a bus has multiple peripherals

[Richard Fitzgerald]

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]);
-
 		}
 	}
 
-- 
2.30.2

[PATCH v4 1/5] soundwire: cadence: fix updating slave status when a bus has multiple peripherals

[Richard Fitzgerald]

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]);
-
 		}
 	}
 
-- 
2.30.2

[PATCH v4 2/5] soundwire: bus: Don't lose unattach notifications

[Richard Fitzgerald]

Ensure that if sdw_handle_slave_status() sees a peripheral
has dropped off the bus it reports it to the client driver.

If there are any devices reporting on address 0 it bails out
after programming the device IDs. So it never reaches the second
loop that calls sdw_update_slave_status().

If the missing device is one that is now showing as unenumerated
it has been given a device ID so will report as attached next
time sdw_handle_slave_status() runs.

With the previous code the client driver would only see another
ATTACHED notification because the UNATTACHED state was lost when
sdw_handle_slave_status() bailed out after programming the
device ID.

This shows up most when the peripheral has to be reset after
downloading updated firmware and there are multiple of these
peripherals on the bus. They will all return to unenumerated state
after the reset, and then there is a mix of unattached, attached
and unenumerated PING states from the peripherals, as each is reset
and they reboot.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 drivers/soundwire/bus.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index d773eee71bc1..1cc858b4107d 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1767,6 +1767,11 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
 			dev_warn(&slave->dev, "Slave %d state check1: UNATTACHED, status was %d\n",
 				 i, slave->status);
 			sdw_modify_slave_status(slave, SDW_SLAVE_UNATTACHED);
+
+			/* Ensure driver knows that peripheral unattached */
+			ret = sdw_update_slave_status(slave, status[i]);
+			if (ret < 0)
+				dev_warn(&slave->dev, "Update Slave status failed:%d\n", ret);
 		}
 	}
 
-- 
2.30.2

[PATCH v4 2/5] soundwire: bus: Don't lose unattach notifications

[Richard Fitzgerald]

Ensure that if sdw_handle_slave_status() sees a peripheral
has dropped off the bus it reports it to the client driver.

If there are any devices reporting on address 0 it bails out
after programming the device IDs. So it never reaches the second
loop that calls sdw_update_slave_status().

If the missing device is one that is now showing as unenumerated
it has been given a device ID so will report as attached next
time sdw_handle_slave_status() runs.

With the previous code the client driver would only see another
ATTACHED notification because the UNATTACHED state was lost when
sdw_handle_slave_status() bailed out after programming the
device ID.

This shows up most when the peripheral has to be reset after
downloading updated firmware and there are multiple of these
peripherals on the bus. They will all return to unenumerated state
after the reset, and then there is a mix of unattached, attached
and unenumerated PING states from the peripherals, as each is reset
and they reboot.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 drivers/soundwire/bus.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index d773eee71bc1..1cc858b4107d 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1767,6 +1767,11 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
 			dev_warn(&slave->dev, "Slave %d state check1: UNATTACHED, status was %d\n",
 				 i, slave->status);
 			sdw_modify_slave_status(slave, SDW_SLAVE_UNATTACHED);
+
+			/* Ensure driver knows that peripheral unattached */
+			ret = sdw_update_slave_status(slave, status[i]);
+			if (ret < 0)
+				dev_warn(&slave->dev, "Update Slave status failed:%d\n", ret);
 		}
 	}
 
-- 
2.30.2

[PATCH v4 3/5] soundwire: bus: Don't re-enumerate before status is UNATTACHED

[Richard Fitzgerald]

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
-- 
2.30.2

[PATCH v4 3/5] soundwire: bus: Don't re-enumerate before status is UNATTACHED

[Richard Fitzgerald]

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
-- 
2.30.2

[PATCH v4 4/5] soundwire: cadence: Fix lost ATTACHED interrupts when enumerating

[Richard Fitzgerald]

The correct way to handle interrupts is to clear the bits we
are about to handle _before_ handling them. Thus if the condition
then re-asserts during the handling we won't lose it.

This patch changes cdns_update_slave_status_work() to do this.

The previous code cleared the interrupts after handling them.
The problem with this is that when handling enumeration of devices
the ATTACH statuses can be accidentally cleared and so some or all
of the devices never complete their enumeration.

Thus we can have a situation like this:
- one or more devices are reverting to ID #0

- accumulated status bits indicate some devices attached and some
  on ID #0. (Remember: status bits are sticky until they are handled)

- Because of device on #0 sdw_handle_slave_status() programs the
  device ID and exits without handling the other status, expecting
  to get an ATTACHED from this reprogrammed device.

- The device immediately starts reporting ATTACHED in PINGs, which
  will assert its CDNS_MCP_SLAVE_INTSTAT_ATTACHED bit.

- cdns_update_slave_status_work() clears INTSTAT0/1. If the initial
  status had CDNS_MCP_SLAVE_INTSTAT_ATTACHED bit set it will be
  cleared.

- The ATTACHED change for the device has now been lost.

- cdns_update_slave_status_work() clears CDNS_MCP_INT_SLAVE_MASK so
  if the new ATTACHED state had set it, it will be cleared without
  ever having been handled.

Unless there is some other state change from another device to cause
a new interrupt, the ATTACHED state of the reprogrammed device will
never cause an interrupt so its enumeration will not be completed.

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 | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 245191d22ccd..be9cd47f31ec 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -954,9 +954,22 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 	u32 device0_status;
 	int retry_count = 0;
 
+	/*
+	 * Clear main interrupt first so we don't lose any assertions
+	 * that happen during this function.
+	 */
+	cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_SLAVE_MASK);
+
 	slave0 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT0);
 	slave1 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT1);
 
+	/*
+	 * Clear the bits before handling so we don't lose any
+	 * bits that re-assert.
+	 */
+	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT0, slave0);
+	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT1, slave1);
+
 	/* combine the two status */
 	slave_intstat = ((u64)slave1 << 32) | slave0;
 
@@ -964,8 +977,6 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 
 update_status:
 	cdns_update_slave_status(cdns, slave_intstat);
-	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT0, slave0);
-	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT1, slave1);
 
 	/*
 	 * When there is more than one peripheral per link, it's
@@ -982,6 +993,11 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 	 * attention with PING commands. There is no need to check for
 	 * ALERTS since they are not allowed until a non-zero
 	 * device_number is assigned.
+	 *
+	 * Do not clear the INTSTAT0/1. While looping to enumerate devices on
+	 * #0 there could be status changes on other devices - these must
+	 * be kept in the INTSTAT so they can be handled when all #0 devices
+	 * have been handled.
 	 */
 
 	device0_status = cdns_readl(cdns, CDNS_MCP_SLAVE_STAT);
@@ -1001,8 +1017,7 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 		}
 	}
 
-	/* clear and unmask Slave interrupt now */
-	cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_SLAVE_MASK);
+	/* unmask Slave interrupt now */
 	cdns_updatel(cdns, CDNS_MCP_INTMASK,
 		     CDNS_MCP_INT_SLAVE_MASK, CDNS_MCP_INT_SLAVE_MASK);
 
-- 
2.30.2

[PATCH v4 4/5] soundwire: cadence: Fix lost ATTACHED interrupts when enumerating

[Richard Fitzgerald]

The correct way to handle interrupts is to clear the bits we
are about to handle _before_ handling them. Thus if the condition
then re-asserts during the handling we won't lose it.

This patch changes cdns_update_slave_status_work() to do this.

The previous code cleared the interrupts after handling them.
The problem with this is that when handling enumeration of devices
the ATTACH statuses can be accidentally cleared and so some or all
of the devices never complete their enumeration.

Thus we can have a situation like this:
- one or more devices are reverting to ID #0

- accumulated status bits indicate some devices attached and some
  on ID #0. (Remember: status bits are sticky until they are handled)

- Because of device on #0 sdw_handle_slave_status() programs the
  device ID and exits without handling the other status, expecting
  to get an ATTACHED from this reprogrammed device.

- The device immediately starts reporting ATTACHED in PINGs, which
  will assert its CDNS_MCP_SLAVE_INTSTAT_ATTACHED bit.

- cdns_update_slave_status_work() clears INTSTAT0/1. If the initial
  status had CDNS_MCP_SLAVE_INTSTAT_ATTACHED bit set it will be
  cleared.

- The ATTACHED change for the device has now been lost.

- cdns_update_slave_status_work() clears CDNS_MCP_INT_SLAVE_MASK so
  if the new ATTACHED state had set it, it will be cleared without
  ever having been handled.

Unless there is some other state change from another device to cause
a new interrupt, the ATTACHED state of the reprogrammed device will
never cause an interrupt so its enumeration will not be completed.

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 | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 245191d22ccd..be9cd47f31ec 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -954,9 +954,22 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 	u32 device0_status;
 	int retry_count = 0;
 
+	/*
+	 * Clear main interrupt first so we don't lose any assertions
+	 * that happen during this function.
+	 */
+	cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_SLAVE_MASK);
+
 	slave0 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT0);
 	slave1 = cdns_readl(cdns, CDNS_MCP_SLAVE_INTSTAT1);
 
+	/*
+	 * Clear the bits before handling so we don't lose any
+	 * bits that re-assert.
+	 */
+	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT0, slave0);
+	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT1, slave1);
+
 	/* combine the two status */
 	slave_intstat = ((u64)slave1 << 32) | slave0;
 
@@ -964,8 +977,6 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 
 update_status:
 	cdns_update_slave_status(cdns, slave_intstat);
-	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT0, slave0);
-	cdns_writel(cdns, CDNS_MCP_SLAVE_INTSTAT1, slave1);
 
 	/*
 	 * When there is more than one peripheral per link, it's
@@ -982,6 +993,11 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 	 * attention with PING commands. There is no need to check for
 	 * ALERTS since they are not allowed until a non-zero
 	 * device_number is assigned.
+	 *
+	 * Do not clear the INTSTAT0/1. While looping to enumerate devices on
+	 * #0 there could be status changes on other devices - these must
+	 * be kept in the INTSTAT so they can be handled when all #0 devices
+	 * have been handled.
 	 */
 
 	device0_status = cdns_readl(cdns, CDNS_MCP_SLAVE_STAT);
@@ -1001,8 +1017,7 @@ static void cdns_update_slave_status_work(struct work_struct *work)
 		}
 	}
 
-	/* clear and unmask Slave interrupt now */
-	cdns_writel(cdns, CDNS_MCP_INTSTAT, CDNS_MCP_INT_SLAVE_MASK);
+	/* unmask Slave interrupt now */
 	cdns_updatel(cdns, CDNS_MCP_INTMASK,
 		     CDNS_MCP_INT_SLAVE_MASK, CDNS_MCP_INT_SLAVE_MASK);
 
-- 
2.30.2

[PATCH v4 5/5] soundwire: bus: Don't exit early if no device IDs were programmed

[Richard Fitzgerald]

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>
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 */
-- 
2.30.2

[PATCH v4 5/5] soundwire: bus: Don't exit early if no device IDs were programmed

[Richard Fitzgerald]

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>
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 */
-- 
2.30.2

Re: [PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

[Vinod Koul]

On 14-09-22, 17:02, Richard Fitzgerald wrote:
> The bus and cadence code has several bugs that cause UNATTACH notifications
> to either be sent spuriously or to be missed.
> 
> These can be seen occasionally with a single peripheral on the bus, but are
> much more frequent with multiple peripherals, where several peripherals
> could change state and report in consecutive PINGs.
> 
> The root of all of these bugs seems to be a code design flaw that assumed
> every PING status change would be handled separately. However, PINGs are
> handled by a workqueue function and there is no guarantee when that function
> will be scheduled to run or how much CPU time it will receive. PINGs will
> continue while the work function is handling a snapshot of a previous PING
> so the code must take account that (a) status could change during the
> work function and (b) there can be a backlog of changes before the IRQ work
> function runs again.

Applied, thanks

-- 
~Vinod

Re: [PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

[Vinod Koul]

On 14-09-22, 17:02, Richard Fitzgerald wrote:
> The bus and cadence code has several bugs that cause UNATTACH notifications
> to either be sent spuriously or to be missed.
> 
> These can be seen occasionally with a single peripheral on the bus, but are
> much more frequent with multiple peripherals, where several peripherals
> could change state and report in consecutive PINGs.
> 
> The root of all of these bugs seems to be a code design flaw that assumed
> every PING status change would be handled separately. However, PINGs are
> handled by a workqueue function and there is no guarantee when that function
> will be scheduled to run or how much CPU time it will receive. PINGs will
> continue while the work function is handling a snapshot of a previous PING
> so the code must take account that (a) status could change during the
> work function and (b) there can be a backlog of changes before the IRQ work
> function runs again.

Applied, thanks

-- 
~Vinod