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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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9c06f26ba5
With this change each pwmchip defining the new-style waveform callbacks can be accessed from userspace via a character device. Compared to the sysfs-API this is faster and allows to pass the whole configuration in a single ioctl allowing atomic application and thus reducing glitches. On an STM32MP13 I see: root@DistroKit:~ time pwmtestperf real 0m 1.27s user 0m 0.02s sys 0m 1.21s root@DistroKit:~ rm /dev/pwmchip0 root@DistroKit:~ time pwmtestperf real 0m 3.61s user 0m 0.27s sys 0m 3.26s pwmtestperf does essentially: for i in 0 .. 50000: pwm_set_waveform(duty_length_ns=i, period_length_ns=50000, duty_offset_ns=0) and in the presence of /dev/pwmchip0 is uses the ioctls introduced here, without that device it uses /sys/class/pwm/pwmchip0. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com> Link: https://lore.kernel.org/r/ad4a4e49ae3f8ea81e23cac1ac12b338c3bf5c5b.1746010245.git.u.kleine-koenig@baylibre.com Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
54 lines
1.7 KiB
C
54 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
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#ifndef _UAPI_PWM_H_
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#define _UAPI_PWM_H_
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#include <linux/ioctl.h>
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#include <linux/types.h>
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/**
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* struct pwmchip_waveform - Describe a PWM waveform for a pwm_chip's PWM channel
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* @hwpwm: per-chip relative index of the PWM device
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* @__pad: padding, must be zero
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* @period_length_ns: duration of the repeating period.
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* A value of 0 represents a disabled PWM.
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* @duty_length_ns: duration of the active part in each period
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* @duty_offset_ns: offset of the rising edge from a period's start
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*/
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struct pwmchip_waveform {
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__u32 hwpwm;
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__u32 __pad;
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__u64 period_length_ns;
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__u64 duty_length_ns;
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__u64 duty_offset_ns;
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};
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/* Reserves the passed hwpwm for exclusive control. */
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#define PWM_IOCTL_REQUEST _IO(0x75, 1)
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/* counter part to PWM_IOCTL_REQUEST */
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#define PWM_IOCTL_FREE _IO(0x75, 2)
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/*
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* Modifies the passed wf according to hardware constraints. All parameters are
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* rounded down to the next possible value, unless there is no such value, then
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* values are rounded up. Note that zero isn't considered for rounding down
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* period_length_ns.
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*/
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#define PWM_IOCTL_ROUNDWF _IOWR(0x75, 3, struct pwmchip_waveform)
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/* Get the currently implemented waveform */
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#define PWM_IOCTL_GETWF _IOWR(0x75, 4, struct pwmchip_waveform)
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/* Like PWM_IOCTL_ROUNDWF + PWM_IOCTL_SETEXACTWF in one go. */
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#define PWM_IOCTL_SETROUNDEDWF _IOW(0x75, 5, struct pwmchip_waveform)
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/*
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* Program the PWM to emit exactly the passed waveform, subject only to rounding
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* down each value less than 1 ns. Returns 0 on success, -EDOM if the waveform
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* cannot be implemented exactly, or other negative error codes.
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*/
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#define PWM_IOCTL_SETEXACTWF _IOW(0x75, 6, struct pwmchip_waveform)
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#endif /* _UAPI_PWM_H_ */
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