vctrl_enable() and vctrl_disable() call regulator_enable() and
regulator_disable(), respectively. However, vctrl_* are regulator ops
and should not be calling the locked regulator APIs. Doing so results in
a lockdep warning.
Instead of exporting more internal regulator ops, model the ctrl supply
as an actual supply to vctrl-regulator. At probe time this driver still
needs to use the consumer API to fetch its constraints, but otherwise
lets the regulator core handle the upstream supply for it.
The enable/disable/is_enabled ops are not removed, but now only track
state internally. This preserves the original behavior with the ops
being available, but one could argue that the original behavior was
already incorrect: the internal state would not match the upstream
supply if that supply had another consumer that enabled the supply,
while vctrl-regulator was not enabled.
The lockdep warning is as follows:
WARNING: possible circular locking dependency detected
5.14.0-rc6 #2 Not tainted
------------------------------------------------------
swapper/0/1 is trying to acquire lock:
ffffffc011306d00 (regulator_list_mutex){+.+.}-{3:3}, at:
regulator_lock_dependent (arch/arm64/include/asm/current.h:19
include/linux/ww_mutex.h:111
drivers/regulator/core.c:329)
but task is already holding lock:
ffffff8004a77160 (regulator_ww_class_mutex){+.+.}-{3:3}, at:
regulator_lock_recursive (drivers/regulator/core.c:156
drivers/regulator/core.c:263)
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (regulator_ww_class_mutex){+.+.}-{3:3}:
__mutex_lock_common (include/asm-generic/atomic-instrumented.h:606
include/asm-generic/atomic-long.h:29
kernel/locking/mutex.c:103
kernel/locking/mutex.c:144
kernel/locking/mutex.c:963)
ww_mutex_lock (kernel/locking/mutex.c:1199)
regulator_lock_recursive (drivers/regulator/core.c:156
drivers/regulator/core.c:263)
regulator_lock_dependent (drivers/regulator/core.c:343)
regulator_enable (drivers/regulator/core.c:2808)
set_machine_constraints (drivers/regulator/core.c:1536)
regulator_register (drivers/regulator/core.c:5486)
devm_regulator_register (drivers/regulator/devres.c:196)
reg_fixed_voltage_probe (drivers/regulator/fixed.c:289)
platform_probe (drivers/base/platform.c:1427)
[...]
-> #1 (regulator_ww_class_acquire){+.+.}-{0:0}:
regulator_lock_dependent (include/linux/ww_mutex.h:129
drivers/regulator/core.c:329)
regulator_enable (drivers/regulator/core.c:2808)
set_machine_constraints (drivers/regulator/core.c:1536)
regulator_register (drivers/regulator/core.c:5486)
devm_regulator_register (drivers/regulator/devres.c:196)
reg_fixed_voltage_probe (drivers/regulator/fixed.c:289)
[...]
-> #0 (regulator_list_mutex){+.+.}-{3:3}:
__lock_acquire (kernel/locking/lockdep.c:3052 (discriminator 4)
kernel/locking/lockdep.c:3174 (discriminator 4)
kernel/locking/lockdep.c:3789 (discriminator 4)
kernel/locking/lockdep.c:5015 (discriminator 4))
lock_acquire (arch/arm64/include/asm/percpu.h:39
kernel/locking/lockdep.c:438
kernel/locking/lockdep.c:5627)
__mutex_lock_common (include/asm-generic/atomic-instrumented.h:606
include/asm-generic/atomic-long.h:29
kernel/locking/mutex.c:103
kernel/locking/mutex.c:144
kernel/locking/mutex.c:963)
mutex_lock_nested (kernel/locking/mutex.c:1125)
regulator_lock_dependent (arch/arm64/include/asm/current.h:19
include/linux/ww_mutex.h:111
drivers/regulator/core.c:329)
regulator_enable (drivers/regulator/core.c:2808)
vctrl_enable (drivers/regulator/vctrl-regulator.c:400)
_regulator_do_enable (drivers/regulator/core.c:2617)
_regulator_enable (drivers/regulator/core.c:2764)
regulator_enable (drivers/regulator/core.c:308
drivers/regulator/core.c:2809)
_set_opp (drivers/opp/core.c:819 drivers/opp/core.c:1072)
dev_pm_opp_set_rate (drivers/opp/core.c:1164)
set_target (drivers/cpufreq/cpufreq-dt.c:62)
__cpufreq_driver_target (drivers/cpufreq/cpufreq.c:2216
drivers/cpufreq/cpufreq.c:2271)
cpufreq_online (drivers/cpufreq/cpufreq.c:1488 (discriminator 2))
cpufreq_add_dev (drivers/cpufreq/cpufreq.c:1563)
subsys_interface_register (drivers/base/bus.c:?)
cpufreq_register_driver (drivers/cpufreq/cpufreq.c:2819)
dt_cpufreq_probe (drivers/cpufreq/cpufreq-dt.c:344)
[...]
other info that might help us debug this:
Chain exists of:
regulator_list_mutex --> regulator_ww_class_acquire --> regulator_ww_class_mutex
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(regulator_ww_class_mutex);
lock(regulator_ww_class_acquire);
lock(regulator_ww_class_mutex);
lock(regulator_list_mutex);
*** DEADLOCK ***
6 locks held by swapper/0/1:
#0: ffffff8002d32188 (&dev->mutex){....}-{3:3}, at:
__device_driver_lock (drivers/base/dd.c:1030)
#1: ffffffc0111a0520 (cpu_hotplug_lock){++++}-{0:0}, at:
cpufreq_register_driver (drivers/cpufreq/cpufreq.c:2792 (discriminator 2))
#2: ffffff8002a8d918 (subsys mutex#9){+.+.}-{3:3}, at:
subsys_interface_register (drivers/base/bus.c:1033)
#3: ffffff800341bb90 (&policy->rwsem){+.+.}-{3:3}, at:
cpufreq_online (include/linux/bitmap.h:285
include/linux/cpumask.h:405
drivers/cpufreq/cpufreq.c:1399)
#4: ffffffc011f0b7b8 (regulator_ww_class_acquire){+.+.}-{0:0}, at:
regulator_enable (drivers/regulator/core.c:2808)
#5: ffffff8004a77160 (regulator_ww_class_mutex){+.+.}-{3:3}, at:
regulator_lock_recursive (drivers/regulator/core.c:156
drivers/regulator/core.c:263)
stack backtrace:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.14.0-rc6 #2 7c8f8996d021ed0f65271e6aeebf7999de74a9fa
Hardware name: Google Scarlet (DT)
Call trace:
dump_backtrace (arch/arm64/kernel/stacktrace.c:161)
show_stack (arch/arm64/kernel/stacktrace.c:218)
dump_stack_lvl (lib/dump_stack.c:106 (discriminator 2))
dump_stack (lib/dump_stack.c:113)
print_circular_bug (kernel/locking/lockdep.c:?)
check_noncircular (kernel/locking/lockdep.c:?)
__lock_acquire (kernel/locking/lockdep.c:3052 (discriminator 4)
kernel/locking/lockdep.c:3174 (discriminator 4)
kernel/locking/lockdep.c:3789 (discriminator 4)
kernel/locking/lockdep.c:5015 (discriminator 4))
lock_acquire (arch/arm64/include/asm/percpu.h:39
kernel/locking/lockdep.c:438
kernel/locking/lockdep.c:5627)
__mutex_lock_common (include/asm-generic/atomic-instrumented.h:606
include/asm-generic/atomic-long.h:29
kernel/locking/mutex.c:103
kernel/locking/mutex.c:144
kernel/locking/mutex.c:963)
mutex_lock_nested (kernel/locking/mutex.c:1125)
regulator_lock_dependent (arch/arm64/include/asm/current.h:19
include/linux/ww_mutex.h:111
drivers/regulator/core.c:329)
regulator_enable (drivers/regulator/core.c:2808)
vctrl_enable (drivers/regulator/vctrl-regulator.c:400)
_regulator_do_enable (drivers/regulator/core.c:2617)
_regulator_enable (drivers/regulator/core.c:2764)
regulator_enable (drivers/regulator/core.c:308
drivers/regulator/core.c:2809)
_set_opp (drivers/opp/core.c:819 drivers/opp/core.c:1072)
dev_pm_opp_set_rate (drivers/opp/core.c:1164)
set_target (drivers/cpufreq/cpufreq-dt.c:62)
__cpufreq_driver_target (drivers/cpufreq/cpufreq.c:2216
drivers/cpufreq/cpufreq.c:2271)
cpufreq_online (drivers/cpufreq/cpufreq.c:1488 (discriminator 2))
cpufreq_add_dev (drivers/cpufreq/cpufreq.c:1563)
subsys_interface_register (drivers/base/bus.c:?)
cpufreq_register_driver (drivers/cpufreq/cpufreq.c:2819)
dt_cpufreq_probe (drivers/cpufreq/cpufreq-dt.c:344)
[...]
Reported-by: Brian Norris <briannorris@chromium.org>
Fixes: f8702f9e4a ("regulator: core: Use ww_mutex for regulators locking")
Fixes: e915331149 ("regulator: vctrl-regulator: Avoid deadlock getting and setting the voltage")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20210825033704.3307263-3-wenst@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>
21e39809fd