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Message-ID: <b95d0de2-1a97-36f0-03ad-3b5e52b1fa5d@microchip.com>
Date: Fri, 14 Sep 2018 18:20:48 +0200
From: Nicolas Ferre <nicolas.ferre@...rochip.com>
To: Claudiu Beznea <claudiu.beznea@...rochip.com>,
<thierry.reding@...il.com>, <alexandre.belloni@...tlin.com>,
<linux-pwm@...r.kernel.org>, <treding@...dia.com>
CC: <shc_work@...l.ru>, <robh+dt@...nel.org>, <mark.rutland@....com>,
<corbet@....net>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [RESEND PATCH v5 0/9] extend PWM framework to support PWM modes
Thierry,
On 28/08/2018 at 15:01, 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].
This series started with a RFC back on 5 April 2017 "extend PWM
framework to support PWM modes". The continuous work starting with v2 of
this series on January 12, 2018.
Then Claudiu tried to address all comments up to v4 which didn't have
any more reviews. He posted a v5 without comments since May 22, 2018.
This series is basically a resent of the v5 (as said in the $subject).
We would like to know what is preventing this series to be included in
the PWM sub-system. Note that if some issue still remain with it, we are
ready to help to solve them.
Without feedback from you side, we fear that we would miss a merge
window again for no obvious reason (DT part is Acked by Rob: patch 5/9).
Best regards,
Nicolas
> 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 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(-)
>
--
Nicolas Ferre
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