Re: [PATCH v5 0/9] extend PWM framework to support PWM modes

[Claudiu Beznea]

Hi Thierry,

It's been a while since I submitted this version but no feedback so far on
it. I re-done it as you suggested. Do you have any thoughts on this version?

Thank you,
Claudiu beznea

On 22.05.2018 15:07, Claudiu Beznea wrote:
> Hi,
> 
> 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 PWM modes support for 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 v5:
> - solved kbuild errors by removing dummy functions for case where
>   CONFIG_PWM is not defined; adopted this approach since the removed
>   function are used only only when CONFIG_PWM is defined (in PWM core
>   and few drivers from drivers/pwm/ directory)
> 
> Changes in v4:
> - removed changes related to pwm_config() as per maintainer proposals
> - added pwm_mode_get_valid() to retrieve a valid PWM mode fror PWM device
>   instead of using BIT(ffs(caps.mode) - 1) and changed drivers to use
>   pwm_mode_get_valid() instead of pwm_get_caps() + BIT(ffs(caps.mode) - 1)
>   (patches 2, 3, 4 from this series)
> - renamed PWM_MODE() macro in PWMC_MODE() to avoid conflicts with
>   pwm-sun4i.c driver ('C' stands for capability)
> - removed pwm_caps_valid() function
> - renamed PWM_DTMODE_COMPLEMENTARY and PWM_DTMODE_PUSH_PULL macros in
>   PWM_MODE_COMPLEMENTARY and PWM_MODE_PUSH_PULL
> 
> 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 (9):
>   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 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 ++++++++-
>  drivers/pwm/core.c                            | 125 +++++++++++++++++++++++++-
>  drivers/pwm/pwm-atmel.c                       | 118 +++++++++++++++++-------
>  drivers/pwm/pwm-clps711x.c                    |  10 ++-
>  drivers/pwm/pwm-cros-ec.c                     |   1 +
>  drivers/pwm/pwm-pxa.c                         |   1 +
>  drivers/pwm/sysfs.c                           |  61 +++++++++++++
>  include/dt-bindings/pwm/pwm.h                 |   2 +
>  include/linux/pwm.h                           |  64 +++++++++++++
>  10 files changed, 395 insertions(+), 40 deletions(-)
>