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Date: Wed, 18 Jul 2018 10:07:16 +0300
From: Claudiu Beznea <Claudiu.Beznea@...rochip.com>
To: <thierry.reding@...il.com>, <shc_work@...l.ru>,
<robh+dt@...nel.org>, <mark.rutland@....com>, <corbet@....net>,
<nicolas.ferre@...rochip.com>,
<alexandre.belloni@...e-electrons.com>
CC: <linux-pwm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 0/9] extend PWM framework to support PWM modes
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@...a5d2-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@...a5d2-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@...a5d2-xplained:/sys/class/pwm/pwmchip0/pwm2# echo normal > mode
> root@...a5d2-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(-)
>
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