[PATCH v2 0/2] Add SoundWire detach helper

[PATCH v2 0/2] Add SoundWire detach helper

[Charles Keepax]

Currently, if a SoundWire driver takes an action that causes the device
to detach from the bus it needs to be careful. There will be a period of
time until the detach is recognised by the core, if the driver
immediately
calls sdw_slave_wait_for_init() it is possible for that to complete
before the detach has been recognised. Leaving the driver with a device
that is potentially not ready for what follows.

To avoid this race add a new helper that drivers can use to inform the
core the device will detach. This clears the enumeration completions
ensuring that sdw_slave_wait_for_init() can't complete until the device
re-attaches.

This is the third part of a longer series of moving these slave
attach/deatach operations into the core:

https://lore.kernel.org/linux-sound/20260512103022.1154645-1-ckeepax@opensource.cirrus.com/
https://lore.kernel.org/linux-sound/20260608102714.2503120-1-ckeepax@opensource.cirrus.com/

I have based this series off Vinod's soundwire tree as that probably
makes sense for which tree to take it through.

Thanks,
Charles

Changes since v1:
 - Correct kerneldoc

Charles Keepax (2):
  soundwire: Add a helper function to indicate a device will detach
  mfd: cs42l43: Move to core detach helper

 drivers/mfd/cs42l43-sdw.c     |  2 --
 drivers/mfd/cs42l43.c         | 15 +--------------
 drivers/soundwire/bus.h       |  6 ------
 include/linux/mfd/cs42l43.h   |  1 -
 include/linux/soundwire/sdw.h | 26 ++++++++++++++++++++++++++
 5 files changed, 27 insertions(+), 23 deletions(-)

-- 
2.47.3

[PATCH v2 1/2] soundwire: Add a helper function to indicate a device will detach

[Charles Keepax]

SoundWire devices will sometimes need to reset themselves,
typical times might include when taking over the device to ensure
a consistent state or after downloading a firmware update to boot
into the new version. Often such a reset will also result in the
device detaching from the SoundWire bus, in this case the driver
has to be careful. Naively calling sdw_slave_wait_for_init()
after doing the reset could immediately succeed if the bus hasn't
seen the detach yet, causing the driver to proceed attempting
to communicate with the device whilst it is detached.

Add a helper function that a driver can call to indicate it is
about to initiate an action that will cause the device to detach
from the bus. This will reinit the completions in the peripheral
for device attach, ensuring that the next sdw_slave_wait_for_init()
will not complete before the detach has been seen by the core.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
---

Changes since v1:
 - Correct kernel doc

 drivers/soundwire/bus.h       |  6 ------
 include/linux/soundwire/sdw.h | 26 ++++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index 44e4f51939176..59b6aee0ea6eb 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -231,12 +231,6 @@ static inline void sdw_fill_port_params(struct sdw_port_params *params,
 int sdw_bread_no_pm_unlocked(struct sdw_bus *bus, u16 dev_num, u32 addr);
 int sdw_bwrite_no_pm_unlocked(struct sdw_bus *bus, u16 dev_num, u32 addr, u8 value);
 
-/*
- * At the moment we only track Master-initiated hw_reset.
- * Additional fields can be added as needed
- */
-#define SDW_UNATTACH_REQUEST_MASTER_RESET	BIT(0)
-
 void sdw_clear_slave_status(struct sdw_bus *bus, u32 request);
 int sdw_slave_modalias(const struct sdw_slave *slave, char *buf, size_t size);
 void sdw_compute_slave_ports(struct sdw_master_runtime *m_rt,
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 707ca6bd1e23d..7d41df30561cf 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -25,6 +25,13 @@ struct device_node;
 struct sdw_bus;
 struct sdw_slave;
 
+/*
+ * At the moment we only track Master-initiated/Slave-initiated hw_reset.
+ * Additional fields can be added as needed
+ */
+#define SDW_UNATTACH_REQUEST_MASTER_RESET	BIT(0)
+#define SDW_UNATTACH_REQUEST_SLAVE_RESET	BIT(1)
+
 /* SDW spec defines and enums, as defined by MIPI 1.1. Spec */
 
 /* SDW Broadcast Device Number */
@@ -1214,6 +1221,25 @@ static inline int sdw_update_no_pm(struct sdw_slave *slave, u32 addr, u8 mask, u
 
 #endif /* CONFIG_SOUNDWIRE */
 
+/**
+ * sdw_slave_signal_unattach - Signal that the peripheral is about to detach
+ * @slave: Pointer to the SoundWire peripheral.
+ *
+ * Inform the core that the peripheral is about to detach from the bus, this
+ * is usually due to some implementation defined reset mechanism. After this
+ * sdw_slave_wait_for_init() should be called to wait for the device to
+ * return.
+ */
+static inline void sdw_slave_signal_unattach(struct sdw_slave *slave)
+{
+	if (!slave)
+		return;
+
+	slave->unattach_request = SDW_UNATTACH_REQUEST_SLAVE_RESET;
+	reinit_completion(&slave->enumeration_complete);
+	reinit_completion(&slave->initialization_complete);
+}
+
 /**
  * sdw_slave_wait_for_init - Wait for device initialisation
  * @slave: Pointer to the SoundWire peripheral.
-- 
2.47.3

[PATCH v2 2/2] mfd: cs42l43: Move to core detach helper

[Charles Keepax]

Now the core has a helper to signal a device will detach from
the SoundWire bus, there is no need for the cs42l43 driver code
to separately track that. Switch to using the new core helper.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
---

No changes since v1.

 drivers/mfd/cs42l43-sdw.c   |  2 --
 drivers/mfd/cs42l43.c       | 15 +--------------
 include/linux/mfd/cs42l43.h |  1 -
 3 files changed, 1 insertion(+), 17 deletions(-)

diff --git a/drivers/mfd/cs42l43-sdw.c b/drivers/mfd/cs42l43-sdw.c
index 0a6999453f325..f0825d6bf7b38 100644
--- a/drivers/mfd/cs42l43-sdw.c
+++ b/drivers/mfd/cs42l43-sdw.c
@@ -102,8 +102,6 @@ static int cs42l43_sdw_update_status(struct sdw_slave *sdw, enum sdw_slave_statu
 		break;
 	case SDW_SLAVE_UNATTACHED:
 		dev_dbg(cs42l43->dev, "Device detach\n");
-
-		complete(&cs42l43->device_detach);
 		break;
 	default:
 		break;
diff --git a/drivers/mfd/cs42l43.c b/drivers/mfd/cs42l43.c
index 4212ebcca60b5..f08ee598366d9 100644
--- a/drivers/mfd/cs42l43.c
+++ b/drivers/mfd/cs42l43.c
@@ -30,7 +30,6 @@
 #define CS42L43_RESET_DELAY_MS			20
 
 #define CS42L43_SDW_ATTACH_TIMEOUT_MS		5000
-#define CS42L43_SDW_DETACH_TIMEOUT_MS		100
 
 #define CS42L43_MCU_BOOT_STAGE1			1
 #define CS42L43_MCU_BOOT_STAGE2			2
@@ -555,7 +554,7 @@ static int cs42l43_soft_reset(struct cs42l43 *cs42l43)
 		{ CS42L43_SFT_RESET, CS42L43_SFT_RESET_VAL },
 	};
 
-	reinit_completion(&cs42l43->device_detach);
+	sdw_slave_signal_unattach(cs42l43->sdw);
 
 	/*
 	 * Apply cache only because the soft reset will cause the device to
@@ -566,17 +565,6 @@ static int cs42l43_soft_reset(struct cs42l43 *cs42l43)
 
 	msleep(CS42L43_RESET_DELAY_MS);
 
-	if (cs42l43->sdw) {
-		unsigned long timeout = msecs_to_jiffies(CS42L43_SDW_DETACH_TIMEOUT_MS);
-		unsigned long time;
-
-		time = wait_for_completion_timeout(&cs42l43->device_detach, timeout);
-		if (!time) {
-			dev_err(cs42l43->dev, "Timed out waiting for device detach\n");
-			return -ETIMEDOUT;
-		}
-	}
-
 	return -EAGAIN;
 }
 
@@ -1115,7 +1103,6 @@ int cs42l43_dev_probe(struct cs42l43 *cs42l43)
 	dev_set_drvdata(cs42l43->dev, cs42l43);
 
 	mutex_init(&cs42l43->pll_lock);
-	init_completion(&cs42l43->device_detach);
 	init_completion(&cs42l43->firmware_download);
 	INIT_WORK(&cs42l43->boot_work, cs42l43_boot_work);
 
diff --git a/include/linux/mfd/cs42l43.h b/include/linux/mfd/cs42l43.h
index 8e993fb535e68..798dc55149662 100644
--- a/include/linux/mfd/cs42l43.h
+++ b/include/linux/mfd/cs42l43.h
@@ -86,7 +86,6 @@ struct cs42l43 {
 	struct regmap_irq_chip_data *irq_data;
 
 	struct work_struct boot_work;
-	struct completion device_detach;
 	struct completion firmware_download;
 	int firmware_error;
 
-- 
2.47.3

Re: [PATCH v2 0/2] Add SoundWire detach helper

[Pierre-Louis Bossart]

On 8/31/26 16:01, Charles Keepax wrote:
> Currently, if a SoundWire driver takes an action that causes the device
> to detach from the bus it needs to be careful. There will be a period of
> time until the detach is recognised by the core, if the driver
> immediately
> calls sdw_slave_wait_for_init() it is possible for that to complete
> before the detach has been recognised. Leaving the driver with a device
> that is potentially not ready for what follows.
> 
> To avoid this race add a new helper that drivers can use to inform the
> core the device will detach. This clears the enumeration completions
> ensuring that sdw_slave_wait_for_init() can't complete until the device
> re-attaches.
> 
> This is the third part of a longer series of moving these slave
> attach/deatach operations into the core:
> 
> https://lore.kernel.org/linux-sound/20260512103022.1154645-1-ckeepax@opensource.cirrus.com/
> https://lore.kernel.org/linux-sound/20260608102714.2503120-1-ckeepax@opensource.cirrus.com/
> 
> I have based this series off Vinod's soundwire tree as that probably
> makes sense for which tree to take it through.
> 
> Thanks,
> Charles
> 
> Changes since v1:
>  - Correct kerneldoc
> 
> Charles Keepax (2):
>   soundwire: Add a helper function to indicate a device will detach
>   mfd: cs42l43: Move to core detach helper
> 
>  drivers/mfd/cs42l43-sdw.c     |  2 --
>  drivers/mfd/cs42l43.c         | 15 +--------------
>  drivers/soundwire/bus.h       |  6 ------
>  include/linux/mfd/cs42l43.h   |  1 -
>  include/linux/soundwire/sdw.h | 26 ++++++++++++++++++++++++++
>  5 files changed, 27 insertions(+), 23 deletions(-)

LGTM, for the series

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>