Hi all,
Please give feedback on these patches which extends the PWM framework in order to support multiple PWM modes of operations. This series is a rework of [1] and [2].
The current patch series add the following PWM modes: - PWM mode normal - PWM mode complementary - PWM mode push-pull
Normal mode - for PWM channels with one output; output waveforms looks like this: __ __ __ __ PWM __| |__| |__| |__| |__ <--T-->
Where T is the signal period
Since PWMs with more than one output per channel could be used as one output PWM the normal mode is the default mode for all PWMs (if not specified otherwise).
Complementary mode - for PWM channels with two outputs; output waveforms for a PWM channel in complementary mode looks line this: __ __ __ __ PWMH1 __| |__| |__| |__| |__ __ __ __ __ __ PWML1 |__| |__| |__| |__| <--T-->
Where T is the signal period.
Push-pull mode - for PWM channels with two outputs; output waveforms for a PWM channel in push-pull mode with normal polarity looks like this: __ __ PWMH __| |________| |________ __ __ PWML ________| |________| |__ <--T-->
If polarity is inversed: __ ________ ________ PWMH |__| |__| ________ ________ __ PWML |__| |__| <--T-->
Where T is the signal period.
The PWM working modes are per PWM channel registered as PWM's capabilities. The driver registers itself to PWM core a get_caps() function, in struct pwm_ops, that will be used by PWM core to retrieve PWM capabilities. If this function is not registered in driver's probe, a default function will be used to retrieve PWM capabilities. Currently, the default capabilities includes only PWM normal mode.
PWM state has been updated to keep PWM mode. PWM mode could be configured via sysfs or via DT. pwm_apply_state() will do the preliminary validation for PWM mode to be applied.
In sysfs, user could get PWM modes by reading mode file of PWM device: root@sama5d2-xplained:/sys/class/pwm/pwmchip0/pwm2# ls -l total 0 -r--r--r-- 1 root root 4096 Oct 9 09:07 capture lrwxrwxrwx 1 root root 0 Oct 9 09:07 device -> ../../pwmchip0 -rw-r--r-- 1 root root 4096 Oct 9 08:42 duty_cycle -rw-r--r-- 1 root root 4096 Oct 9 08:44 enable --w------- 1 root root 4096 Oct 9 09:07 export -rw-r--r-- 1 root root 4096 Oct 9 08:43 mode -r--r--r-- 1 root root 4096 Oct 9 09:07 npwm -rw-r--r-- 1 root root 4096 Oct 9 08:42 period -rw-r--r-- 1 root root 4096 Oct 9 08:44 polarity drwxr-xr-x 2 root root 0 Oct 9 09:07 power lrwxrwxrwx 1 root root 0 Oct 9 09:07 subsystem -> ../../../../../../../../class/pwm -rw-r--r-- 1 root root 4096 Oct 9 08:42 uevent --w------- 1 root root 4096 Oct 9 09:07 unexport root@sama5d2-xplained:/sys/class/pwm/pwmchip0/pwm2# cat mode normal complementary [push-pull]
The mode enclosed in bracket is the currently active mode.
The mode could be set, via sysfs, by writing to mode file one of the modes displayed at read: root@sama5d2-xplained:/sys/class/pwm/pwmchip0/pwm2# echo normal > mode root@sama5d2-xplained:/sys/class/pwm/pwmchip0/pwm2# cat mode [normal] complementary push-pull
The PWM push-pull mode could be usefull in applications like half bridge converters.
This series also add support for PWM modes on Atmel/Microchip SoCs.
Thank you, Claudiu Beznea
[1] https://www.spinics.net/lists/arm-kernel/msg580275.html [2] https://lkml.org/lkml/2018/1/12/359
Changes in v3: - removed changes related to only one of_xlate function for all PWM drivers - switch to PWM capabilities per PWM channel nor per PWM chip - squash documentation and bindings patches as requeted by reviewer - introduced PWM_MODE(name) macro and used a bit enum for pwm modes - related to DT bindings, used flags cell also for PWM modes - updated of_xlate specific functions with "state->mode = mode;" instructions to avoid pwm_apply_state() failures - use available modes for PWM channel in pwm_config() by first calling pwm_get_caps() to get caps.modes - use loops through available modes in mode_store()/mode_show() and also in of_pwm_xlate_with_flags() instead of "if else" instructions; in this way, the addition of a new mode is independent of this code sections - use DTLI=1, DTHI=0 register settings to obtain push-pull mode waveforms for Atmel/Microchip PWM controller.
Changes in v2: - remove of_xlate and of_pwm_n_cells and use generic functions to pharse DT inputs; this is done in patches 1, 2, 3, 4, 5, 6, 7 of this series; this will make easy the addition of PWM mode support from DT - add PWM mode normal - register PWM modes as capabilities of PWM chips at driver probe and, in case driver doesn't provide these capabilities use default ones - change the way PWM mode is pharsed via DT by using a new input for pwms binding property
Claudiu Beznea (10): pwm: extend PWM framework with PWM modes pwm: clps711x: populate PWM mode in of_xlate function pwm: cros-ec: populate PWM mode in of_xlate function pwm: pxa: populate PWM mode in of_xlate function pwm: add PWM mode to pwm_config() pwm: add PWM modes pwm: atmel: add pwm capabilities pwm: add push-pull mode support pwm: add documentation for pwm push-pull mode pwm: atmel: add push-pull mode support
Documentation/devicetree/bindings/pwm/pwm.txt | 11 ++- Documentation/pwm.txt | 42 ++++++++- arch/arm/mach-s3c24xx/mach-rx1950.c | 11 ++- drivers/bus/ts-nbus.c | 2 +- drivers/clk/clk-pwm.c | 3 +- drivers/gpu/drm/i915/intel_panel.c | 17 +++- drivers/hwmon/pwm-fan.c | 2 +- drivers/input/misc/max77693-haptic.c | 2 +- drivers/input/misc/max8997_haptic.c | 6 +- drivers/leds/leds-pwm.c | 5 +- drivers/media/rc/ir-rx51.c | 5 +- drivers/media/rc/pwm-ir-tx.c | 5 +- drivers/pwm/core.c | 98 ++++++++++++++++++++- drivers/pwm/pwm-atmel.c | 118 +++++++++++++++++++------- drivers/pwm/pwm-clps711x.c | 12 ++- drivers/pwm/pwm-cros-ec.c | 4 + drivers/pwm/pwm-pxa.c | 4 + drivers/pwm/sysfs.c | 56 ++++++++++++ drivers/video/backlight/lm3630a_bl.c | 4 +- drivers/video/backlight/lp855x_bl.c | 4 +- drivers/video/backlight/lp8788_bl.c | 5 +- drivers/video/backlight/pwm_bl.c | 11 ++- drivers/video/fbdev/ssd1307fb.c | 3 +- include/dt-bindings/pwm/pwm.h | 2 + include/linux/pwm.h | 100 +++++++++++++++++++++- 25 files changed, 470 insertions(+), 62 deletions(-)