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It's possible that the auxiliary proxy device we add when setting up the
GPIO controller exposing shared pins, will get matched and probed
immediately. The gpio-proxy-driver will then retrieve the shared
descriptor structure. That will cause a recursive mutex locking and
a deadlock because we're already holding the gpio_shared_lock in
gpio_device_setup_shared() and try to take it again in
devm_gpiod_shared_get() like this:
[ 4.298346] gpiolib_shared: GPIO 130 owned by f100000.pinctrl is shared by multiple consumers
[ 4.307157] gpiolib_shared: Setting up a shared GPIO entry for speaker@0,3
[ 4.314604]
[ 4.316146] ============================================
[ 4.321600] WARNING: possible recursive locking detected
[ 4.327054] 6.18.0-rc7-next-20251125-g3f300d0674f6-dirty #3887 Not tainted
[ 4.334115] --------------------------------------------
[ 4.339566] kworker/u32:3/71 is trying to acquire lock:
[ 4.344931] ffffda019ba71850 (gpio_shared_lock){+.+.}-{4:4}, at: devm_gpiod_shared_get+0x34/0x2e0
[ 4.354057]
[ 4.354057] but task is already holding lock:
[ 4.360041] ffffda019ba71850 (gpio_shared_lock){+.+.}-{4:4}, at: gpio_device_setup_shared+0x30/0x268
[ 4.369421]
[ 4.369421] other info that might help us debug this:
[ 4.376126] Possible unsafe locking scenario:
[ 4.376126]
[ 4.382198] CPU0
[ 4.384711] ----
[ 4.387223] lock(gpio_shared_lock);
[ 4.390992] lock(gpio_shared_lock);
[ 4.394761]
[ 4.394761] *** DEADLOCK ***
[ 4.394761]
[ 4.400832] May be due to missing lock nesting notation
[ 4.400832]
[ 4.407802] 5 locks held by kworker/u32:3/71:
[ 4.412279] #0: ffff000080020948 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x194/0x64c
[ 4.422650] #1: ffff800080963d60 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1bc/0x64c
[ 4.432117] #2: ffff00008165c8f8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x3c/0x198
[ 4.440700] #3: ffffda019ba71850 (gpio_shared_lock){+.+.}-{4:4}, at: gpio_device_setup_shared+0x30/0x268
[ 4.450523] #4: ffff0000810fe918 (&dev->mutex){....}-{4:4}, at: __device_attach+0x3c/0x198
[ 4.459103]
[ 4.459103] stack backtrace:
[ 4.463581] CPU: 6 UID: 0 PID: 71 Comm: kworker/u32:3 Not tainted 6.18.0-rc7-next-20251125-g3f300d0674f6-dirty #3887 PREEMPT
[ 4.463589] Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
[ 4.463593] Workqueue: events_unbound deferred_probe_work_func
[ 4.463602] Call trace:
[ 4.463604] show_stack+0x18/0x24 (C)
[ 4.463617] dump_stack_lvl+0x70/0x98
[ 4.463627] dump_stack+0x18/0x24
[ 4.463636] print_deadlock_bug+0x224/0x238
[ 4.463643] __lock_acquire+0xe4c/0x15f0
[ 4.463648] lock_acquire+0x1cc/0x344
[ 4.463653] __mutex_lock+0xb8/0x840
[ 4.463661] mutex_lock_nested+0x24/0x30
[ 4.463667] devm_gpiod_shared_get+0x34/0x2e0
[ 4.463674] gpio_shared_proxy_probe+0x18/0x138
[ 4.463682] auxiliary_bus_probe+0x40/0x78
[ 4.463688] really_probe+0xbc/0x2c0
[ 4.463694] __driver_probe_device+0x78/0x120
[ 4.463701] driver_probe_device+0x3c/0x160
[ 4.463708] __device_attach_driver+0xb8/0x140
[ 4.463716] bus_for_each_drv+0x88/0xe8
[ 4.463723] __device_attach+0xa0/0x198
[ 4.463729] device_initial_probe+0x14/0x20
[ 4.463737] bus_probe_device+0xb4/0xc0
[ 4.463743] device_add+0x578/0x76c
[ 4.463747] __auxiliary_device_add+0x40/0xac
[ 4.463752] gpio_device_setup_shared+0x1f8/0x268
[ 4.463758] gpiochip_add_data_with_key+0xdac/0x10ac
[ 4.463763] devm_gpiochip_add_data_with_key+0x30/0x80
[ 4.463768] msm_pinctrl_probe+0x4b0/0x5e0
[ 4.463779] sm8250_pinctrl_probe+0x18/0x40
[ 4.463784] platform_probe+0x5c/0xa4
[ 4.463793] really_probe+0xbc/0x2c0
[ 4.463800] __driver_probe_device+0x78/0x120
[ 4.463807] driver_probe_device+0x3c/0x160
[ 4.463814] __device_attach_driver+0xb8/0x140
[ 4.463821] bus_for_each_drv+0x88/0xe8
[ 4.463827] __device_attach+0xa0/0x198
[ 4.463834] device_initial_probe+0x14/0x20
[ 4.463841] bus_probe_device+0xb4/0xc0
[ 4.463847] deferred_probe_work_func+0x90/0xcc
[ 4.463854] process_one_work+0x214/0x64c
[ 4.463860] worker_thread+0x1bc/0x360
[ 4.463866] kthread+0x14c/0x220
[ 4.463871] ret_from_fork+0x10/0x20
[ 77.265041] random: crng init done
Fortunately, at the time of creating of the auxiliary device, we already
know the correct entry so let's store it as the device's platform data.
We don't need to hold gpio_shared_lock in devm_gpiod_shared_get() as
we're not removing the entry or traversing the list anymore but we still
need to protect it from concurrent modification of its fields so add a
more fine-grained mutex.
Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
Reported-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Closes: https://lore.kernel.org/all/fimuvblfy2cmn7o4wzcxjzrux5mwhvlvyxfsgeqs6ore2xg75i@ax46d3sfmdux/
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20251128-gpio-shared-deadlock-v2-1-9f3ae8ddcb09@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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GPIO hogs have a "gpios" property but it's not a phandle to a remote
node - it references the parent GPIO controller. We must not try to
parse it as a phandle.
Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
Reported-by: Cosmin Tanislav <demonsingur@gmail.com>
Closes: https://lore.kernel.org/all/2d96e464-e17c-4ff5-9a08-b215b77da04f@gmail.com/
Link: https://lore.kernel.org/r/20251126-gpio-shared-fixes-v1-2-18309c0e87b5@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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The __symbols__ node is a special, internal node and its properties must
not be considered when scanning the device-tree for shared GPIOs.
Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Closes: https://lore.kernel.org/all/0829a21c-f97d-41b6-90bc-2acaec42caab@nvidia.com/
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20251126-gpio-shared-fixes-v1-1-18309c0e87b5@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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There's an unexpected interaction between the reset-gpio driver and the
shared GPIO support. The reset-gpio device is an auxiliary device that's
created dynamically and fulfills a similar role to the gpio-shared-proxy
driver but is limited in scope to just supporting the "reset-gpios"
property.
The shared GPIO core code does not take into account that the machine
lookup entry we create when scanning the device-tree must connect the
reset-gpio device - that is the actual consumer of the GPIO and not the
consumer defined on the device tree, which in turn consumes the shared
reset control exposed by the reset-gpio device - to the GPIO controller.
We also must not skip the gpio-shared-proxy driver as it's possible that
a shared GPIO may be used by one consumer as a reset-gpios going through
the reset-gpio device and another that uses GPIOLIB.
We need to make it a special case handled in gpiolib-shared.c. Add a new
function - gpio_shared_dev_is_reset_gpio() - whose role it is to verify
if a non-matching consumer of a shared pin is a reset-gpio device and
make sure it's the right one for this pin. To that end make sure that
its parent is the GPIO controller in question and that the fwnode we
identified as sharing the pin references that controller via the
"reset-gpios" property.
Only include that code if the reset-gpio driver is enabled.
Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
Reported-by: Val Packett <val@packett.cool>
Closes: https://lore.kernel.org/all/3b5d9df5-934d-4591-8827-6c9573a6f7ba@packett.cool/
Tested-by: Val Packett <val@packett.cool>
Tested-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20251125-gpiolib-shared-reset-gpio-fix-v2-1-4eb6fa41f1dd@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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While this function is supposed to be used by all scanning functions, so
far we only have a single one for OF trees. Once we add support for ACPI
and software nodes, we'll drop the CONFIG_OF guard around this routine
but in order to avoid build warnings, let's extend it to cover it in the
meantime.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511180232.EItKeYjY-lkp@intel.com/
Link: https://lore.kernel.org/r/20251118-gpiolib-shared-of-guard-v1-1-e4ef149a2e0b@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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The fact that CONFIG_OF is enabled does not mean that the device tree is
populated and that of_root points to a valid device node. Check if it's
NULL before trying to traverse the tree.
Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/dbe20642-9662-40af-a593-c1263baea73b@sirena.org.uk/
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20251118200459.13969-1-brgl@bgdev.pl
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git into gpio/for-next
Immutable branch between the GPIO, ASoC and regulator trees for v6.19-rc1
Add better support for GPIOs shared by multiple consumers.
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Provide an interface allowing consumers to check if a GPIO descriptor
represents a GPIO that can potentially be shared by multiple consumers
at the same time. This is exposed to allow subsystems that already
work around the limitations of the current non-exclusive GPIO handling
in some ways, to gradually convert to relying on the new shared GPIO
feature of GPIOLIB.
Extend the gpiolib-shared module to mark the GPIO shared proxy
descriptors with a flag checked by the new interface.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20251112-gpio-shared-v4-6-b51f97b1abd8@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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This module scans the device tree (for now only OF nodes are supported
but care is taken to make other fwnode implementations easy to
integrate) and determines which GPIO lines are shared by multiple users.
It stores that information in memory. When the GPIO chip exposing shared
lines is registered, the shared GPIO descriptors it exposes are marked
as shared and virtual "proxy" devices that mediate access to the shared
lines are created. When a consumer of a shared GPIO looks it up, its
fwnode lookup is redirected to a just-in-time machine lookup that points
to this proxy device.
This code can be compiled out on platforms which don't use shared GPIOs.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20251112-gpio-shared-v4-3-b51f97b1abd8@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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