[PATCH v9 0/3] lan966x pci device: Add support for SFPs, i2c part

[PATCH v9 0/3] lan966x pci device: Add support for SFPs, i2c part

[Herve Codina]

Hi,

Previously, I sent a big picture series adding support for SFP ports
available on the LAN966x PCI device [0].

In this series patches touch several parts and sub-system in the kernel.
Reviews have be done and it makes sense to split the series and send
parts separately.

This current series is the extraction of patches related to issues in
the I2C subsystem. It has to be seen as a continuation of the big
picture series but related to this specific I2C part.

Those patches are related fw_delink issues specific to I2C muxes and
atrs.

They purpose is to correctly set a link between an adapter supplier and
its consumer. Indeed, an i2c mux/atr adapter's parent is not the i2c
mux/atr supplier but the adapter the i2c mux/atr is connected to. Adding
a new link between the adapter supplier involved when i2c muxes/atrs are
used avoid a freeze observed during device removal.

[0] https://lore.kernel.org/all/20260325143555.451852-1-herve.codina@bootlin.com/

Compared to the previous iteration, this v9 iteration updates i2c-atr.c
with the same modification done in i2c-mux.c. Indeed, atr and mux are
pretty similar and the exact same modifications for the exact same
reason can be done in both files (reported in v8 by Peter Rosin).

If having both atr and mux modifications in one commits is not
acceptable, let me know and I will split them in different commits.

Worth noting that I tested modifications done in mux but not in atr.
Indeed, I don't have any atr devices on the different board I have to
perform a test.

Best regards,
Hervé

Changes:

v8 -> v9
  v8: https://lore.kernel.org/all/20260630103010.413688-1-herve.codina@bootlin.com/
  Rebase on top of v7.4-rc1

  Patches 2 and 3
  - Add same modifications in i2c-atr.c than the ones done in i2c-mux.c.
  - Update commit logs accordingly.

v7 -> v8
  v7: https://lore.kernel.org/all/20260605083158.28ac874f@bootlin.com/

  Rebase on top of v7.2-rc1
  No other changes

v6 -> v7

  Rebase on top of v7.1-rc1

  - Patch 1, 2 and 3
    No changes

Older iterations:
  Patches 14, 15 and 16in the big picture series
  https://lore.kernel.org/all/20260325143555.451852-1-herve.codina@bootlin.com/

Herve Codina (3):
  i2c: core: Introduce i2c_get_adapter_physdev()
  i2c: {mux,atr}: Set adapter physical device
  i2c: {mux,atr}: Create missing devlink between mux/atr and adapter
    physical device

 drivers/i2c/i2c-atr.c       | 26 ++++++++++++++++++++++++++
 drivers/i2c/i2c-core-base.c | 16 ++++++++++++++++
 drivers/i2c/i2c-mux.c       | 26 ++++++++++++++++++++++++++
 include/linux/i2c.h         |  3 +++
 4 files changed, 71 insertions(+)

-- 
2.56.0

[PATCH v9 1/3] i2c: core: Introduce i2c_get_adapter_physdev()

[Herve Codina]

The physical device providing an I2C adapter is the device that calls
i2c_add_adapter() or variants and i2c_del_adapter().

Most of the time this physical device is the parent of the adapter
device.

Exceptions exist with i2c muxes. Indeed, in case of i2c muxes, the
parent of the mux adapter device points to the adapter device the mux is
connected to instead of the physical of this mux adapter.

Introduce i2c_get_adapter_physdev() and a new physdev field in the
adapter structure in order to ease the adapter physical device
retrieval.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
---
 drivers/i2c/i2c-core-base.c | 16 ++++++++++++++++
 include/linux/i2c.h         |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 165ec14260c8..0c08b0e71609 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1956,6 +1956,22 @@ struct i2c_adapter *i2c_get_adapter_by_fwnode(struct fwnode_handle *fwnode)
 }
 EXPORT_SYMBOL(i2c_get_adapter_by_fwnode);
 
+/**
+ * i2c_get_adapter_physdev() - Get the physical device of an adapter
+ * @adapter: the adapter to get the physical device from
+ *
+ * Return:
+ * Look up and return the &struct device corresponding to the device supplying
+ * this @adapter.
+ *
+ * The user must call put_device() once done with the physical device returned.
+ */
+struct device *i2c_get_adapter_physdev(struct i2c_adapter *adapter)
+{
+	return get_device(adapter->physdev ?: adapter->dev.parent);
+}
+EXPORT_SYMBOL(i2c_get_adapter_physdev);
+
 static void i2c_parse_timing(struct device *dev, char *prop_name, u32 *cur_val_p,
 			    u32 def_val, bool use_def)
 {
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 6a847fc88d25..bcf2e4e30108 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -762,6 +762,7 @@ struct i2c_adapter {
 #endif
 	int retries;
 	struct device dev;		/* the adapter device */
+	struct device *physdev;		/* the physical device */
 	unsigned long locked_flags;	/* owned by the I2C core */
 #define I2C_ALF_IS_SUSPENDED		0
 #define I2C_ALF_SUSPEND_REPORTED	1
@@ -929,6 +930,8 @@ struct i2c_adapter *i2c_get_adapter(int nr);
 void i2c_put_adapter(struct i2c_adapter *adap);
 unsigned int i2c_adapter_depth(struct i2c_adapter *adapter);
 
+struct device *i2c_get_adapter_physdev(struct i2c_adapter *adap);
+
 void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults);
 
 #ifdef CONFIG_I2C_DYNAMIC_TIMEOUT
-- 
2.56.0

[PATCH v9 2/3] i2c: {mux,atr}: Set adapter physical device

[Herve Codina]

For i2c muxes and atrs (address translators), the parent of the mux/atr
adapter device is the adapter device the mux/atr is connected to.

This parent is not the physical device related to the mux/atr adapter.
Indeed, the physical device of the mux/atr adapter is the mux/atr device
itself.

Fill the adap.physdev with the mux/atr device.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
---
 drivers/i2c/i2c-atr.c | 1 +
 drivers/i2c/i2c-mux.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index b98442ffff94..a591d39050e7 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/drivers/i2c/i2c-atr.c
@@ -824,6 +824,7 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
 	chan->adap.algo = &atr->algo;
 	chan->adap.algo_data = chan;
 	chan->adap.dev.parent = desc->parent;
+	chan->adap.physdev = dev;
 	chan->adap.retries = parent->retries;
 	chan->adap.timeout = parent->timeout;
 	chan->adap.quirks = parent->quirks;
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 53428098ddc7..c1836114ef56 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -361,6 +361,7 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	priv->adap.algo = &priv->algo;
 	priv->adap.algo_data = priv;
 	priv->adap.dev.parent = &parent->dev;
+	priv->adap.physdev = muxc->dev;
 	priv->adap.retries = parent->retries;
 	priv->adap.timeout = parent->timeout;
 	priv->adap.quirks = parent->quirks;
-- 
2.56.0

[PATCH v9 3/3] i2c: {mux,atr}: Create missing devlink between mux/atr and adapter physical device

[Herve Codina]

When removing an i2c controller device handling an i2c bus where an i2c
mux is connected to, the removal process hangs and is stuck in the
wait_completion() call done in i2c_del_adapter().

The i2c_del_adapter() tries to removed the i2c adapter related to the
i2c controller device and the wait_completion() is waiting for the i2c
adapter device release. This release is performed when the device is no
more used (i.e. refcount reaches zero).

When an i2c mux (and/or atr) is involved in an i2c path, the struct dev
topology is the following:

    +----------------+                +-------------------+
    | i2c controller |                |    i2c mux/atr    |
    |     device     |                |      device       |
    |       ^        |                |                   |
    |       |        |                |                   |
    |  dev's parent  |                |                   |
    |       |        |                |                   |
    |   i2c adapter  |                | i2c adapter chanX |
    |     device  <---- dev's parent ------  device       |
    |   (no driver)  |                |    (no driver)    |
    +----------------+                +-------------------+

When an i2c mux/atr device creates an i2c adapter for its downstream
channel, a reference is taken to its adapter dev's parent. This parent
is the i2c mux/atr upstream adapter device.

No relationship exists between the i2c mux/atr device itself and the i2c
controller device (physical device) in order to have the i2c mux/atr
device calling i2c_del_adapter() to remove its downstream adapters and so,
release references taken to the upstream adapter.

This consumer/supplier relationship is typically a devlink relationship.

Also, i2c muxes/atrs can be chained and so, the upstream adapter can be
supplied by either an i2c controller device or an other i2c mux/atr
device.

In order to get the physical device of the adapter a mux/atr is
connected to, rely on the newly introduced i2c_adapter_get_physdev() and
create the missing devlink between the i2c mux/atr device and the
physical device of the adapter the mux/atr is connected to.

With that done, the i2c mux/atr device is removed before the device
handling the upstream i2c adapter (i2c controller device or i2c mux/atr
device). All references are released and the i2c_del_adapter() call
performed by driver handling the upstream adapter device is not blocking
anymore.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/i2c/i2c-atr.c | 25 +++++++++++++++++++++++++
 drivers/i2c/i2c-mux.c | 25 +++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index a591d39050e7..94ff543d4f8e 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/drivers/i2c/i2c-atr.c
@@ -788,9 +788,11 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
 	struct fwnode_handle *bus_handle = desc->bus_handle;
 	struct i2c_adapter *parent = atr->parent;
 	char symlink_name[ATR_MAX_SYMLINK_LEN];
+	struct device *parent_physdev;
 	struct device *dev = atr->dev;
 	u32 chan_id = desc->chan_id;
 	struct i2c_atr_chan *chan;
+	struct device_link *dl;
 	int ret, idx;
 
 	if (chan_id >= atr->max_adapters) {
@@ -866,6 +868,29 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
 
 	atr->adapter[chan_id] = &chan->adap;
 
+	/*
+	 * There is no relationship set between the atr device and the physical
+	 * device handling the parent adapter. Create this missing relationship
+	 * in order to remove the i2c atr device (consumer) and so the dowstream
+	 * channel adapters before removing the physical device (supplier) which
+	 * handles the i2c atr upstream adapter.
+	 */
+	parent_physdev = i2c_get_adapter_physdev(parent);
+	if (!parent_physdev) {
+		dev_err(dev, "failed to get the parent physical device\n");
+		ret = -ENODEV;
+		goto err_free_alias_pool;
+	}
+	dl = device_link_add(dev, parent_physdev, DL_FLAG_AUTOREMOVE_CONSUMER);
+	if (!dl) {
+		dev_err(dev, "failed to create device link to %s\n",
+			dev_name(parent_physdev));
+		put_device(parent_physdev);
+		ret = -EINVAL;
+		goto err_free_alias_pool;
+	}
+	put_device(parent_physdev);
+
 	ret = i2c_add_adapter(&chan->adap);
 	if (ret) {
 		atr->adapter[chan_id] = NULL;
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index c1836114ef56..0cfb581b4ef1 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -314,7 +314,9 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 			u32 force_nr, u32 chan_id)
 {
 	struct i2c_adapter *parent = muxc->parent;
+	struct device *parent_physdev;
 	struct i2c_mux_priv *priv;
+	struct device_link *dl;
 	char symlink_name[20];
 	int ret;
 
@@ -382,6 +384,29 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 				      ACPI_COMPANION(muxc->dev),
 				      chan_id);
 
+	/*
+	 * There is no relationship set between the mux device and the physical
+	 * device handling the parent adapter. Create this missing relationship
+	 * in order to remove the i2c mux device (consumer) and so the dowstream
+	 * channel adapters before removing the physical device (supplier) which
+	 * handles the i2c mux upstream adapter.
+	 */
+	parent_physdev = i2c_get_adapter_physdev(parent);
+	if (!parent_physdev) {
+		dev_err(muxc->dev, "failed to get the parent physical device\n");
+		ret = -ENODEV;
+		goto err_free_priv;
+	}
+	dl = device_link_add(muxc->dev, parent_physdev, DL_FLAG_AUTOREMOVE_CONSUMER);
+	if (!dl) {
+		dev_err(muxc->dev, "failed to create device link to %s\n",
+			dev_name(parent_physdev));
+		put_device(parent_physdev);
+		ret = -EINVAL;
+		goto err_free_priv;
+	}
+	put_device(parent_physdev);
+
 	if (force_nr) {
 		priv->adap.nr = force_nr;
 		ret = i2c_add_numbered_adapter(&priv->adap);
-- 
2.56.0