[ 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 <phong.hoang.wz@renesas.com> [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 <yoshihiro.shimoda.uh@renesas.com> Tested-by: Hoan Nguyen An <na-hoan@jinso.co.jp> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Simon Horman <horms+renesas@verge.net.au> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Thierry Reding <thierry.reding@gmail.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
345 lines
8.4 KiB
C
345 lines
8.4 KiB
C
#ifndef __LINUX_PWM_H
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#define __LINUX_PWM_H
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#include <linux/err.h>
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#include <linux/mutex.h>
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#include <linux/of.h>
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struct pwm_device;
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struct seq_file;
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#if IS_ENABLED(CONFIG_PWM)
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/*
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* pwm_request - request a PWM device
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*/
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struct pwm_device *pwm_request(int pwm_id, const char *label);
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/*
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* pwm_free - free a PWM device
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*/
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void pwm_free(struct pwm_device *pwm);
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/*
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* pwm_config - change a PWM device configuration
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*/
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int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
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/*
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* pwm_enable - start a PWM output toggling
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*/
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int pwm_enable(struct pwm_device *pwm);
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/*
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* pwm_disable - stop a PWM output toggling
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*/
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void pwm_disable(struct pwm_device *pwm);
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#else
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static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void pwm_free(struct pwm_device *pwm)
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{
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}
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static inline int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
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{
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return -EINVAL;
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}
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static inline int pwm_enable(struct pwm_device *pwm)
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{
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return -EINVAL;
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}
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static inline void pwm_disable(struct pwm_device *pwm)
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{
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}
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#endif
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struct pwm_chip;
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/**
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* enum pwm_polarity - polarity of a PWM signal
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* @PWM_POLARITY_NORMAL: a high signal for the duration of the duty-
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* cycle, followed by a low signal for the remainder of the pulse
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* period
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* @PWM_POLARITY_INVERSED: a low signal for the duration of the duty-
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* cycle, followed by a high signal for the remainder of the pulse
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* period
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*/
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enum pwm_polarity {
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PWM_POLARITY_NORMAL,
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PWM_POLARITY_INVERSED,
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};
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enum {
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PWMF_REQUESTED = 1 << 0,
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PWMF_ENABLED = 1 << 1,
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PWMF_EXPORTED = 1 << 2,
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};
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/**
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* struct pwm_device - PWM channel object
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* @label: name of the PWM device
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* @flags: flags associated with the PWM device
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* @hwpwm: per-chip relative index of the PWM device
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* @pwm: global index of the PWM device
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* @chip: PWM chip providing this PWM device
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* @chip_data: chip-private data associated with the PWM device
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* @lock: used to serialize accesses to the PWM device where necessary
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* @period: period of the PWM signal (in nanoseconds)
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* @duty_cycle: duty cycle of the PWM signal (in nanoseconds)
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* @polarity: polarity of the PWM signal
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*/
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struct pwm_device {
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const char *label;
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unsigned long flags;
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unsigned int hwpwm;
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unsigned int pwm;
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struct pwm_chip *chip;
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void *chip_data;
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struct mutex lock;
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unsigned int period;
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unsigned int duty_cycle;
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enum pwm_polarity polarity;
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};
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static inline bool pwm_is_enabled(const struct pwm_device *pwm)
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{
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return test_bit(PWMF_ENABLED, &pwm->flags);
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}
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static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
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{
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if (pwm)
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pwm->period = period;
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}
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static inline unsigned int pwm_get_period(const struct pwm_device *pwm)
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{
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return pwm ? pwm->period : 0;
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}
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static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
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{
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if (pwm)
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pwm->duty_cycle = duty;
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}
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static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
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{
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return pwm ? pwm->duty_cycle : 0;
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}
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/*
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* pwm_set_polarity - configure the polarity of a PWM signal
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*/
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int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
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static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
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{
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return pwm ? pwm->polarity : PWM_POLARITY_NORMAL;
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}
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/**
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* struct pwm_ops - PWM controller operations
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* @request: optional hook for requesting a PWM
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* @free: optional hook for freeing a PWM
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* @config: configure duty cycles and period length for this PWM
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* @set_polarity: configure the polarity of this PWM
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* @enable: enable PWM output toggling
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* @disable: disable PWM output toggling
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* @dbg_show: optional routine to show contents in debugfs
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* @owner: helps prevent removal of modules exporting active PWMs
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*/
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struct pwm_ops {
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int (*request)(struct pwm_chip *chip, struct pwm_device *pwm);
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void (*free)(struct pwm_chip *chip, struct pwm_device *pwm);
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int (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
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int duty_ns, int period_ns);
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int (*set_polarity)(struct pwm_chip *chip, struct pwm_device *pwm,
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enum pwm_polarity polarity);
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int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
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void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
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#ifdef CONFIG_DEBUG_FS
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void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s);
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#endif
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struct module *owner;
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};
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/**
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* struct pwm_chip - abstract a PWM controller
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* @dev: device providing the PWMs
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* @list: list node for internal use
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* @ops: callbacks for this PWM controller
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* @base: number of first PWM controlled by this chip
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* @npwm: number of PWMs controlled by this chip
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* @pwms: array of PWM devices allocated by the framework
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* @of_xlate: request a PWM device given a device tree PWM specifier
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* @of_pwm_n_cells: number of cells expected in the device tree PWM specifier
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* @can_sleep: must be true if the .config(), .enable() or .disable()
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* operations may sleep
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*/
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struct pwm_chip {
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struct device *dev;
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struct list_head list;
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const struct pwm_ops *ops;
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int base;
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unsigned int npwm;
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struct pwm_device *pwms;
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struct pwm_device * (*of_xlate)(struct pwm_chip *pc,
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const struct of_phandle_args *args);
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unsigned int of_pwm_n_cells;
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bool can_sleep;
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};
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#if IS_ENABLED(CONFIG_PWM)
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int pwm_set_chip_data(struct pwm_device *pwm, void *data);
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void *pwm_get_chip_data(struct pwm_device *pwm);
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int pwmchip_add_with_polarity(struct pwm_chip *chip,
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enum pwm_polarity polarity);
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int pwmchip_add(struct pwm_chip *chip);
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int pwmchip_remove(struct pwm_chip *chip);
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struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
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unsigned int index,
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const char *label);
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struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc,
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const struct of_phandle_args *args);
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struct pwm_device *pwm_get(struct device *dev, const char *con_id);
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struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id);
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void pwm_put(struct pwm_device *pwm);
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struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id);
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struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
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const char *con_id);
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void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
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bool pwm_can_sleep(struct pwm_device *pwm);
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#else
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static inline int pwm_set_chip_data(struct pwm_device *pwm, void *data)
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{
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return -EINVAL;
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}
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static inline void *pwm_get_chip_data(struct pwm_device *pwm)
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{
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return NULL;
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}
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static inline int pwmchip_add(struct pwm_chip *chip)
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{
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return -EINVAL;
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}
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static inline int pwmchip_add_inversed(struct pwm_chip *chip)
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{
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return -EINVAL;
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}
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static inline int pwmchip_remove(struct pwm_chip *chip)
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{
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return -EINVAL;
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}
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static inline struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
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unsigned int index,
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const char *label)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline struct pwm_device *pwm_get(struct device *dev,
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const char *consumer)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline struct pwm_device *of_pwm_get(struct device_node *np,
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const char *con_id)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void pwm_put(struct pwm_device *pwm)
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{
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}
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static inline struct pwm_device *devm_pwm_get(struct device *dev,
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const char *consumer)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline struct pwm_device *devm_of_pwm_get(struct device *dev,
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struct device_node *np,
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const char *con_id)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
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{
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}
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static inline bool pwm_can_sleep(struct pwm_device *pwm)
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{
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return false;
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}
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#endif
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struct pwm_lookup {
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struct list_head list;
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const char *provider;
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unsigned int index;
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const char *dev_id;
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const char *con_id;
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unsigned int period;
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enum pwm_polarity polarity;
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};
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#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
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{ \
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.provider = _provider, \
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.index = _index, \
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.dev_id = _dev_id, \
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.con_id = _con_id, \
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.period = _period, \
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.polarity = _polarity \
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}
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#if IS_ENABLED(CONFIG_PWM)
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void pwm_add_table(struct pwm_lookup *table, size_t num);
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void pwm_remove_table(struct pwm_lookup *table, size_t num);
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#else
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static inline void pwm_add_table(struct pwm_lookup *table, size_t num)
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{
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}
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static inline void pwm_remove_table(struct pwm_lookup *table, size_t num)
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{
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}
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#endif
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#ifdef CONFIG_PWM_SYSFS
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void pwmchip_sysfs_export(struct pwm_chip *chip);
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void pwmchip_sysfs_unexport(struct pwm_chip *chip);
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#else
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static inline void pwmchip_sysfs_export(struct pwm_chip *chip)
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{
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}
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static inline void pwmchip_sysfs_unexport(struct pwm_chip *chip)
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{
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}
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#endif /* CONFIG_PWM_SYSFS */
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#endif /* __LINUX_PWM_H */
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