There is an issue with ACPI overlay table removal specifically related to I2C multiplexers.

Consider an ACPI SSDT Overlay that defines a PCA9548 I2C mux on an existing I2C bus. When this table is loaded we see the creation of a device for the overall PCA9548 chip and 8 further devices - one i2c_adapter each for the mux channels. These are all bound to their ACPI equivalents via an eventual invocation of acpi_bind_one().

When we unload the SSDT overlay we run into the problem. The ACPI devices are deleted as normal via acpi_device_del_work_fn() and the acpi_device_del_list.

However, the following warning and stack trace is output as the deletion does not go smoothly: ------------[ cut here ]------------ kernfs: can not remove 'physical_node', no directory WARNING: CPU: 1 PID: 11 at fs/kernfs/dir.c:1674 kernfs_remove_by_name_ns+0xb9/0xc0 Modules linked in: CPU: 1 PID: 11 Comm: kworker/u128:0 Not tainted 6.8.0-rc6+ #1 Hardware name: congatec AG conga-B7E3/conga-B7E3, BIOS 5.13 05/16/2023 Workqueue: kacpi_hotplug acpi_device_del_work_fn RIP: 0010:kernfs_remove_by_name_ns+0xb9/0xc0 Code: e4 00 48 89 ef e8 07 71 db ff 5b b8 fe ff ff ff 5d 41 5c 41 5d e9 a7 55 e4 00 0f 0b eb a6 48 c7 c7 f0 38 0d 9d e8 97 0a d5 ff <0f> 0b eb dc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 0018:ffff9f864008fb28 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffff8ef90a8d4940 RCX: 0000000000000000 RDX: ffff8f000e267d10 RSI: ffff8f000e25c780 RDI: ffff8f000e25c780 RBP: ffff8ef9186f9870 R08: 0000000000013ffb R09: 00000000ffffbfff R10: 00000000ffffbfff R11: ffff8f000e0a0000 R12: ffff9f864008fb50 R13: ffff8ef90c93dd60 R14: ffff8ef9010d0958 R15: ffff8ef9186f98c8 FS: 0000000000000000(0000) GS:ffff8f000e240000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f48f5253a08 CR3: 00000003cb82e000 CR4: 00000000003506f0 Call Trace: <TASK> ? kernfs_remove_by_name_ns+0xb9/0xc0 ? __warn+0x7c/0x130 ? kernfs_remove_by_name_ns+0xb9/0xc0 ? report_bug+0x171/0x1a0 ? handle_bug+0x3c/0x70 ? exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? kernfs_remove_by_name_ns+0xb9/0xc0 ? kernfs_remove_by_name_ns+0xb9/0xc0 acpi_unbind_one+0x108/0x180 device_del+0x18b/0x490 ? srso_return_thunk+0x5/0x5f ? srso_return_thunk+0x5/0x5f device_unregister+0xd/0x30 i2c_del_adapter.part.0+0x1bf/0x250 i2c_mux_del_adapters+0xa1/0xe0 i2c_device_remove+0x1e/0x80 device_release_driver_internal+0x19a/0x200 bus_remove_device+0xbf/0x100 device_del+0x157/0x490 ? __pfx_device_match_fwnode+0x10/0x10 ? srso_return_thunk+0x5/0x5f device_unregister+0xd/0x30 i2c_acpi_notify+0x10f/0x140 notifier_call_chain+0x58/0xd0 blocking_notifier_call_chain+0x3a/0x60 acpi_device_del_work_fn+0x85/0x1d0 process_one_work+0x134/0x2f0 worker_thread+0x2f0/0x410 ? __pfx_worker_thread+0x10/0x10 kthread+0xe3/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2f/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 </TASK> ---[ end trace 0000000000000000 ]--- ... repeated 7 more times, 1 for each channel of the mux ...

The issue is that the binding of the ACPI devices to their peer I2C adapters is not correctly cleaned up. Digging deeper into the issue we see that the deletion order is such that the ACPI devices matching the mux channel i2c adapters are deleted first during the SSDT overlay removal. For each of the channels we see a call to i2c_acpi_notify() with ACPI_RECONFIG_DEVICE_REMOVE but, because these devices are not actually i2c_clients, nothing is done for them.

Later on, after each of the mux channels has been dealt with, we come to delete the i2c_client representing the PCA9548 device. This is the call stack we see above, whereby the kernel cleans up the i2c_client including destruction of the mux and its channel adapters. At this point we do attempt to unbind from the ACPI peers but those peers no longer exist and so we hit the kernfs errors.

The fix is to augment i2c_acpi_notify() to handle i2c_adapters. But, given that the life cycle of the adapters is linked to the i2c_client, instead of deleting the i2c_adapters during the i2c_acpi_notify(), we just trigger unbinding of the ACPI device from the adapter device, and allow the clean up of the adapter to continue in the way it always has.

Signed-off-by: Hamish Martin hamish.martin@alliedtelesis.co.nz Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Reviewed-by: Andi Shyti andi.shyti@kernel.org Fixes: 525e6fabeae2 ("i2c / ACPI: add support for ACPI reconfigure notifications") Cc: stable@vger.kernel.org # v4.8+ --- drivers/i2c/i2c-core-acpi.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c index d6037a328669..67fa8deccef6 100644 --- a/drivers/i2c/i2c-core-acpi.c +++ b/drivers/i2c/i2c-core-acpi.c @@ -445,6 +445,11 @@ static struct i2c_client *i2c_acpi_find_client_by_adev(struct acpi_device *adev) return i2c_find_device_by_fwnode(acpi_fwnode_handle(adev)); }

+static struct i2c_adapter *i2c_acpi_find_adapter_by_adev(struct acpi_device *adev) +{ + return i2c_find_adapter_by_fwnode(acpi_fwnode_handle(adev)); +} + static int i2c_acpi_notify(struct notifier_block *nb, unsigned long value, void *arg) { @@ -471,11 +476,17 @@ static int i2c_acpi_notify(struct notifier_block *nb, unsigned long value, break;

client = i2c_acpi_find_client_by_adev(adev); - if (!client) - break; + if (client) { + i2c_unregister_device(client); + put_device(&client->dev); + } + + adapter = i2c_acpi_find_adapter_by_adev(adev); + if (adapter) { + acpi_device_notify_remove(&adapter->dev); + put_device(&adapter->dev); + }

- i2c_unregister_device(client); - put_device(&client->dev); break; }