kernel/drivers/pwm, branch linux-5.1.y

pwm: Fix deadlock warning when removing PWM device

2019-06-15T09:53:05Z

[ Upstream commit 347ab9480313737c0f1aaa08e8f2e1a791235535 ] This patch fixes deadlock warning if removing PWM device when CONFIG_PROVE_LOCKING is enabled. This issue can be reproceduced by the following steps on the R-Car H3 Salvator-X board if the backlight is disabled: # cd /sys/class/pwm/pwmchip0 # echo 0 > export # ls device export npwm power pwm0 subsystem uevent unexport # cd device/driver # ls bind e6e31000.pwm uevent unbind # echo e6e31000.pwm > unbind [ 87.659974] ====================================================== [ 87.666149] WARNING: possible circular locking dependency detected [ 87.672327] 5.0.0 #7 Not tainted [ 87.675549] ------------------------------------------------------ [ 87.681723] bash/2986 is trying to acquire lock: [ 87.686337] 000000005ea0e178 (kn->count#58){++++}, at: kernfs_remove_by_name_ns+0x50/0xa0 [ 87.694528] [ 87.694528] but task is already holding lock: [ 87.700353] 000000006313b17c (pwm_lock){+.+.}, at: pwmchip_remove+0x28/0x13c [ 87.707405] [ 87.707405] which lock already depends on the new lock. [ 87.707405] [ 87.715574] [ 87.715574] the existing dependency chain (in reverse order) is: [ 87.723048] [ 87.723048] -> #1 (pwm_lock){+.+.}: [ 87.728017] __mutex_lock+0x70/0x7e4 [ 87.732108] mutex_lock_nested+0x1c/0x24 [ 87.736547] pwm_request_from_chip.part.6+0x34/0x74 [ 87.741940] pwm_request_from_chip+0x20/0x40 [ 87.746725] export_store+0x6c/0x1f4 [ 87.750820] dev_attr_store+0x18/0x28 [ 87.754998] sysfs_kf_write+0x54/0x64 [ 87.759175] kernfs_fop_write+0xe4/0x1e8 [ 87.763615] __vfs_write+0x40/0x184 [ 87.767619] vfs_write+0xa8/0x19c [ 87.771448] ksys_write+0x58/0xbc [ 87.775278] __arm64_sys_write+0x18/0x20 [ 87.779721] el0_svc_common+0xd0/0x124 [ 87.783986] el0_svc_compat_handler+0x1c/0x24 [ 87.788858] el0_svc_compat+0x8/0x18 [ 87.792947] [ 87.792947] -> #0 (kn->count#58){++++}: [ 87.798260] lock_acquire+0xc4/0x22c [ 87.802353] __kernfs_remove+0x258/0x2c4 [ 87.806790] kernfs_remove_by_name_ns+0x50/0xa0 [ 87.811836] remove_files.isra.1+0x38/0x78 [ 87.816447] sysfs_remove_group+0x48/0x98 [ 87.820971] sysfs_remove_groups+0x34/0x4c [ 87.825583] device_remove_attrs+0x6c/0x7c [ 87.830197] device_del+0x11c/0x33c [ 87.834201] device_unregister+0x14/0x2c [ 87.838638] pwmchip_sysfs_unexport+0x40/0x4c [ 87.843509] pwmchip_remove+0xf4/0x13c [ 87.847773] rcar_pwm_remove+0x28/0x34 [ 87.852039] platform_drv_remove+0x24/0x64 [ 87.856651] device_release_driver_internal+0x18c/0x21c [ 87.862391] device_release_driver+0x14/0x1c [ 87.867175] unbind_store+0xe0/0x124 [ 87.871265] drv_attr_store+0x20/0x30 [ 87.875442] sysfs_kf_write+0x54/0x64 [ 87.879618] kernfs_fop_write+0xe4/0x1e8 [ 87.884055] __vfs_write+0x40/0x184 [ 87.888057] vfs_write+0xa8/0x19c [ 87.891887] ksys_write+0x58/0xbc [ 87.895716] __arm64_sys_write+0x18/0x20 [ 87.900154] el0_svc_common+0xd0/0x124 [ 87.904417] el0_svc_compat_handler+0x1c/0x24 [ 87.909289] el0_svc_compat+0x8/0x18 [ 87.913378] [ 87.913378] other info that might help us debug this: [ 87.913378] [ 87.921374] Possible unsafe locking scenario: [ 87.921374] [ 87.927286] CPU0 CPU1 [ 87.931808] ---- ---- [ 87.936331] lock(pwm_lock); [ 87.939293] lock(kn->count#58); [ 87.945120] lock(pwm_lock); [ 87.950599] lock(kn->count#58); [ 87.953908] [ 87.953908] *** DEADLOCK *** [ 87.953908] [ 87.959821] 4 locks held by bash/2986: [ 87.963563] #0: 00000000ace7bc30 (sb_writers#6){.+.+}, at: vfs_write+0x188/0x19c [ 87.971044] #1: 00000000287991b2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xb4/0x1e8 [ 87.978872] #2: 00000000f739d016 (&dev->mutex){....}, at: device_release_driver_internal+0x40/0x21c [ 87.988001] #3: 000000006313b17c (pwm_lock){+.+.}, at: pwmchip_remove+0x28/0x13c [ 87.995481] [ 87.995481] stack backtrace: [ 87.999836] CPU: 0 PID: 2986 Comm: bash Not tainted 5.0.0 #7 [ 88.005489] Hardware name: Renesas Salvator-X board based on r8a7795 ES1.x (DT) [ 88.012791] Call trace: [ 88.015235] dump_backtrace+0x0/0x190 [ 88.018891] show_stack+0x14/0x1c [ 88.022204] dump_stack+0xb0/0xec [ 88.025514] print_circular_bug.isra.32+0x1d0/0x2e0 [ 88.030385] __lock_acquire+0x1318/0x1864 [ 88.034388] lock_acquire+0xc4/0x22c [ 88.037958] __kernfs_remove+0x258/0x2c4 [ 88.041874] kernfs_remove_by_name_ns+0x50/0xa0 [ 88.046398] remove_files.isra.1+0x38/0x78 [ 88.050487] sysfs_remove_group+0x48/0x98 [ 88.054490] sysfs_remove_groups+0x34/0x4c [ 88.058580] device_remove_attrs+0x6c/0x7c [ 88.062671] device_del+0x11c/0x33c [ 88.066154] device_unregister+0x14/0x2c [ 88.070070] pwmchip_sysfs_unexport+0x40/0x4c [ 88.074421] pwmchip_remove+0xf4/0x13c [ 88.078163] rcar_pwm_remove+0x28/0x34 [ 88.081906] platform_drv_remove+0x24/0x64 [ 88.085996] device_release_driver_internal+0x18c/0x21c [ 88.091215] device_release_driver+0x14/0x1c [ 88.095478] unbind_store+0xe0/0x124 [ 88.099048] drv_attr_store+0x20/0x30 [ 88.102704] sysfs_kf_write+0x54/0x64 [ 88.106359] kernfs_fop_write+0xe4/0x1e8 [ 88.110275] __vfs_write+0x40/0x184 [ 88.113757] vfs_write+0xa8/0x19c [ 88.117065] ksys_write+0x58/0xbc [ 88.120374] __arm64_sys_write+0x18/0x20 [ 88.124291] el0_svc_common+0xd0/0x124 [ 88.128034] el0_svc_compat_handler+0x1c/0x24 [ 88.132384] el0_svc_compat+0x8/0x18 The sysfs unexport in pwmchip_remove() is completely asymmetric to what we do in pwmchip_add_with_polarity() and commit 0733424c9ba9 ("pwm: Unexport children before chip removal") is a strong indication that this was wrong to begin with. We should just move pwmchip_sysfs_unexport() where it belongs, which is right after pwmchip_sysfs_unexport_children(). In that case, we do not need separate functions anymore either. We also really want to remove sysfs irrespective of whether or not the chip will be removed as a result of pwmchip_remove(). We can only assume that the driver will be gone after that, so we shouldn't leave any dangling sysfs files around. This warning disappears if we move pwmchip_sysfs_unexport() to the top of pwmchip_remove(), pwmchip_sysfs_unexport_children(). That way it is also outside of the pwm_lock section, which indeed doesn't seem to be needed. Moving the pwmchip_sysfs_export() call outside of that section also seems fine and it'd be perfectly symmetric with pwmchip_remove() again. So, this patch fixes them. Signed-off-by: Phong Hoang [shimoda: revise the commit log and code] Fixes: 76abbdde2d95 ("pwm: Add sysfs interface") Fixes: 0733424c9ba9 ("pwm: Unexport children before chip removal") Signed-off-by: Yoshihiro Shimoda Tested-by: Hoan Nguyen An Reviewed-by: Geert Uytterhoeven Reviewed-by: Simon Horman Reviewed-by: Uwe Kleine-König Signed-off-by: Thierry Reding Signed-off-by: Sasha Levin

pwm: tiehrpwm: Update shadow register for disabling PWMs

2019-06-15T09:53:05Z

[ Upstream commit b00ef53053191d3025c15e8041699f8c9d132daf ] It must be made sure that immediate mode is not already set, when modifying shadow register value in ehrpwm_pwm_disable(). Otherwise modifications to the action-qualifier continuous S/W force register(AQSFRC) will be done in the active register. This may happen when both channels are being disabled. In this case, only the first channel state will be recorded as disabled in the shadow register. Later, when enabling the first channel again, the second channel would be enabled as well. Setting RLDCSF to zero, first, ensures that the shadow register is updated as desired. Fixes: 38dabd91ff0b ("pwm: tiehrpwm: Fix disabling of output of PWMs") Signed-off-by: Christoph Vogtländer [vigneshr@ti.com: Improve commit message] Signed-off-by: Vignesh Raghavendra Signed-off-by: Thierry Reding Signed-off-by: Sasha Levin

pwm: meson: Use the spin-lock only to protect register modifications

2019-06-15T09:52:55Z

[ Upstream commit f173747fffdf037c791405ab4f1ec0eb392fc48e ] Holding the spin-lock for all of the code in meson_pwm_apply() can result in a "BUG: scheduling while atomic". This can happen because clk_get_rate() (which is called from meson_pwm_calc()) may sleep. Only hold the spin-lock when modifying registers to solve this. The reason why we need a spin-lock in the driver is because the REG_MISC_AB register is shared between the two channels provided by one PWM controller. The only functions where REG_MISC_AB is modified are meson_pwm_enable() and meson_pwm_disable() so the register reads/writes in there need to be protected by the spin-lock. The original code also used the spin-lock to protect the values in struct meson_pwm_channel. This could be necessary if two consumers can use the same PWM channel. However, PWM core doesn't allow this so we don't need to protect the values in struct meson_pwm_channel with a lock. Fixes: 211ed630753d2f ("pwm: Add support for Meson PWM Controller") Signed-off-by: Martin Blumenstingl Reviewed-by: Uwe Kleine-König Reviewed-by: Neil Armstrong Signed-off-by: Thierry Reding Signed-off-by: Sasha Levin

pwm: atmel: Remove useless symbolic definitions

2019-03-04T11:52:49Z

The values that these symbols define are only assigned to the per-SoC structure where the context is clear, so there's no need for the extra symbolic name. Acked-by: Claudiu Beznea Signed-off-by: Thierry Reding

pwm: bcm-kona: Update macros to remove braces around numbers

2019-03-04T11:52:49Z

Parentheses are not needed around integer literals in macros. Remove them. Signed-off-by: Sheetal Tigadoli Acked-by: Uwe Kleine-König Signed-off-by: Thierry Reding

pwm: imx27: Only enable the clocks once in .get_state()

2019-03-04T11:52:48Z

Currently the function pwm_imx27_get_state() of enables the clocks once unconditionally at the start, a second time if the PWM is enabled and disables unconditionally at the end. Simplify that to enable once at the start and disable conditionally at the end. Signed-off-by: Uwe Kleine-König Signed-off-by: Thierry Reding

pwm: rcar: Improve calculation of divider

2019-03-04T11:14:21Z

The rcar_pwm_get_clock_division() has a loop to calculate the divider, but the value of div should be calculatable without a loop. So, this patch improves it. This algorithm is suggested by Uwe Kleine-König and Laurent Pinchart. Signed-off-by: Yoshihiro Shimoda Acked-by: Uwe Kleine-König Signed-off-by: Thierry Reding

pwm: rcar: Remove legacy APIs

2019-03-04T11:14:07Z

This patch removes legacy APIs. Since rcar_pwm_{en,dis}able() functions are reused on "atomic" API, this patch changes the arguments of these functions. No change in behavior. Signed-off-by: Yoshihiro Shimoda Acked-by: Uwe Kleine-König Signed-off-by: Thierry Reding

pwm: rcar: Use "atomic" API on rcar_pwm_resume()

2019-03-04T11:14:06Z

To remove legacy API related functions in the future, this patch uses "atomic" related function instead. No change in behavior. Signed-off-by: Yoshihiro Shimoda Acked-by: Uwe Kleine-König Signed-off-by: Thierry Reding

pwm: rcar: Add support "atomic" API

2019-03-04T11:14:05Z

This patch adds support for "atomic" API. This behavior differs with legacy APIs a little. Legacy APIs: The PWMCNT register will be updated in rcar_pwm_config() even if the PWM state is disabled. Atomic API: The PWMCNT register will be updated in rcar_pwm_apply() only if the PWM state is enabled. Otherwize, if a PWM runs with 30% duty cycles and the pwm_apply_state() is called with state->enabled = 0, ->duty_cycle = 60 and ->period = 100, this is possible to output a 60% duty cycle. Signed-off-by: Yoshihiro Shimoda Signed-off-by: Thierry Reding