6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dmitry Baryshkov dmitry.baryshkov@oss.qualcomm.com
[ Upstream commit cf0233491b3a15933234a26efd9ecbc1c0764674 ]
If the PHY driver uses another PHY internally (e.g. in case of eUSB2, repeaters are represented as PHYs), then it would trigger the following lockdep splat because all PHYs use a single static lockdep key and thus lockdep can not identify whether there is a dependency or not and reports a false positive.
Make PHY subsystem use dynamic lockdep keys, assigning each driver a separate key. This way lockdep can correctly identify dependency graph between mutexes.
============================================ WARNING: possible recursive locking detected 6.15.0-rc7-next-20250522-12896-g3932f283970c #3455 Not tainted -------------------------------------------- kworker/u51:0/78 is trying to acquire lock: ffff0008116554f0 (&phy->mutex){+.+.}-{4:4}, at: phy_init+0x4c/0x12c
but task is already holding lock: ffff000813c10cf0 (&phy->mutex){+.+.}-{4:4}, at: phy_init+0x4c/0x12c
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(&phy->mutex); lock(&phy->mutex);
*** DEADLOCK ***
May be due to missing lock nesting notation
4 locks held by kworker/u51:0/78: #0: ffff000800010948 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x18c/0x5ec #1: ffff80008036bdb0 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1b4/0x5ec #2: ffff0008094ac8f8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x38/0x188 #3: ffff000813c10cf0 (&phy->mutex){+.+.}-{4:4}, at: phy_init+0x4c/0x12c
stack backtrace: CPU: 0 UID: 0 PID: 78 Comm: kworker/u51:0 Not tainted 6.15.0-rc7-next-20250522-12896-g3932f283970c #3455 PREEMPT Hardware name: Qualcomm CRD, BIOS 6.0.240904.BOOT.MXF.2.4-00528.1-HAMOA-1 09/ 4/2024 Workqueue: events_unbound deferred_probe_work_func Call trace: show_stack+0x18/0x24 (C) dump_stack_lvl+0x90/0xd0 dump_stack+0x18/0x24 print_deadlock_bug+0x258/0x348 __lock_acquire+0x10fc/0x1f84 lock_acquire+0x1c8/0x338 __mutex_lock+0xb8/0x59c mutex_lock_nested+0x24/0x30 phy_init+0x4c/0x12c snps_eusb2_hsphy_init+0x54/0x1a0 phy_init+0xe0/0x12c dwc3_core_init+0x450/0x10b4 dwc3_core_probe+0xce4/0x15fc dwc3_probe+0x64/0xb0 platform_probe+0x68/0xc4 really_probe+0xbc/0x298 __driver_probe_device+0x78/0x12c driver_probe_device+0x3c/0x160 __device_attach_driver+0xb8/0x138 bus_for_each_drv+0x84/0xe0 __device_attach+0x9c/0x188 device_initial_probe+0x14/0x20 bus_probe_device+0xac/0xb0 deferred_probe_work_func+0x8c/0xc8 process_one_work+0x208/0x5ec worker_thread+0x1c0/0x368 kthread+0x14c/0x20c ret_from_fork+0x10/0x20
Fixes: 3584f6392f09 ("phy: qcom: phy-qcom-snps-eusb2: Add support for eUSB2 repeater") Fixes: e2463559ff1d ("phy: amlogic: Add Amlogic AXG PCIE PHY Driver") Reviewed-by: Neil Armstrong neil.armstrong@linaro.org Reviewed-by: Abel Vesa abel.vesa@linaro.org Reported-by: Johan Hovold johan+linaro@kernel.org Link: https://lore.kernel.org/lkml/ZnpoAVGJMG4Zu-Jw@hovoldconsulting.com/ Reviewed-by: Johan Hovold johan+linaro@kernel.org Tested-by: Johan Hovold johan+linaro@kernel.org Signed-off-by: Dmitry Baryshkov dmitry.baryshkov@oss.qualcomm.com Link: https://lore.kernel.org/r/20250605-phy-subinit-v3-1-1e1e849e10cd@oss.qualcom... Signed-off-by: Vinod Koul vkoul@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/phy/phy-core.c | 5 ++++- include/linux/phy/phy.h | 2 ++ 2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c index 8e2daea81666b..04a5a34e7a950 100644 --- a/drivers/phy/phy-core.c +++ b/drivers/phy/phy-core.c @@ -994,7 +994,8 @@ struct phy *phy_create(struct device *dev, struct device_node *node, }
device_initialize(&phy->dev); - mutex_init(&phy->mutex); + lockdep_register_key(&phy->lockdep_key); + mutex_init_with_key(&phy->mutex, &phy->lockdep_key);
phy->dev.class = &phy_class; phy->dev.parent = dev; @@ -1259,6 +1260,8 @@ static void phy_release(struct device *dev) dev_vdbg(dev, "releasing '%s'\n", dev_name(dev)); debugfs_remove_recursive(phy->debugfs); regulator_put(phy->pwr); + mutex_destroy(&phy->mutex); + lockdep_unregister_key(&phy->lockdep_key); ida_free(&phy_ida, phy->id); kfree(phy); } diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h index e63e6e70e8604..51f781b565655 100644 --- a/include/linux/phy/phy.h +++ b/include/linux/phy/phy.h @@ -149,6 +149,7 @@ struct phy_attrs { * @id: id of the phy device * @ops: function pointers for performing phy operations * @mutex: mutex to protect phy_ops + * @lockdep_key: lockdep information for this mutex * @init_count: used to protect when the PHY is used by multiple consumers * @power_count: used to protect when the PHY is used by multiple consumers * @attrs: used to specify PHY specific attributes @@ -160,6 +161,7 @@ struct phy { int id; const struct phy_ops *ops; struct mutex mutex; + struct lock_class_key lockdep_key; int init_count; int power_count; struct phy_attrs attrs;