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Subject[PATCH v2 0/2] extends PWM framework to support PWM dead-times
Date
Hi all,

Please give feedback on these patches which extends PWM framework
in order to support PWM dead-times.
Since I didn't receive any inputs on RFC series I'm resending it as
normal patch series.

For a PWM controller with more than one output signals per PWM channel
dead-times are the delays introduced between the edges of the output
signals and the original signal introduced in dead-time generator
engine.
E.g. consider a PWM controller with a dead-time engine as in the following
diagram:

-----------------
| |---> PWMH
PWM signal --->| Dead-time engine|
| |---> PWML
-----------------

With no dead-time configured, the PWMH and PWML signals will be
complementary signals (rising and falling edges of PWMH and PWML
have opposite leves, same duration and same starting time) as
follows:

____0 D____P ____ ____ ____
PWM signal __| |____| |____| |____| |____| |___
____ ____ ____ ____ ____
PWMH __| |____| |____| |____| |____| |___
__ ____ ____ ____ ____ ___
PWML |____| |____| |____| |____| |____|

Where - 0 is the starting point of the signal
- D is the starting point of the duty-cycle
- P is the signal period

Based on the above diagram:
- rising edge dead-time - is the delay introduced in one of the
dead-time engine output signals; the delay is introduced after
rising edge of the original PWM signal
- falling edge dead-time - is the delay introduced in one of the
dead-time engine output signals; the delay is introduced after
the end of falling edge of the original PWM signal

The following diagram explain how PWM dead-times falls on some signals:

____0 D____P ____ ____ ____
PWM signal __| |____| |____| |____| |____| |___
__ __ __ __ __
PWMH ____| |____re| |______| |______| |______| |___
__ __ __ __ __ __
PWML |______| |____fe| |______| |______| |______|

In the upper diagram:
- re = rising edge = the delay between D point of the original PWM signal
(rising edge) and the starting point of the next edge of one of the PWM
dead-time engine output
- fe = falling edge = the delay between P point of the original PWM signal
(falling edge) and the starting point of the next edge of one of the PWM
dead-time engine output

To configure the PWM dead-times new inputs were added to sysfs,
in PWM subsystem, one for rising edge dead-time, one for falling
edge deadtime.

root@sama5d2-xplained:/sys/devices/platform/ahb/ahb:apb/f802c000.pwm/pwm/pwmchip0/pwm2# ls -l
-r--r--r-- 1 root root 4096 Feb 10 10:00 capture
-rw-r--r-- 1 root root 4096 Feb 10 10:01 deadtime_fe
-rw-r--r-- 1 root root 4096 Feb 10 10:02 deadtime_re
-rw-r--r-- 1 root root 4096 Feb 10 10:00 duty_cycle
-rw-r--r-- 1 root root 4096 Feb 10 10:00 enable
-rw-r--r-- 1 root root 4096 Feb 10 10:00 period
-rw-r--r-- 1 root root 4096 Feb 10 10:00 polarity
drwxr-xr-x 2 root root 0 Feb 10 10:00 power
-rw-r--r-- 1 root root 4096 Feb 10 10:00 uevent

The PWM dead-times are used in half bridge converters applications.

Thank you,
Claudiu Beznea

Changes since v1:
- fixed compilation warning

Changes since RFC patches:
- corrected the Documentation/pwm.txt
- in atmel-pwm.c check atmel_pwm->regs->dt before computing
dead-times or setting specific registers since the driver is
used by controllers witch supports dead-time configuration and
controller which does not.

Claudiu Beznea (2):
drivers: pwm: core: implement pwm dead-times
drivers: pwm: pwm-atmel: implement pwm dead-times

Documentation/pwm.txt | 55 ++++++++++++++++++++++++++++++++++++
drivers/pwm/core.c | 10 ++++++-
drivers/pwm/pwm-atmel.c | 62 ++++++++++++++++++++++++++++++++++++++---
drivers/pwm/sysfs.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/pwm.h | 36 ++++++++++++++++++++++++
5 files changed, 232 insertions(+), 5 deletions(-)

--
2.7.4

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