Re: [PATCH v6 0/8] Add PWM and IIO timer drivers for STM32

[Lee Jones]

On Fri, 09 Dec 2016, Benjamin Gaignard wrote:

> version 6:
> - rename stm32-gptimer in stm32-timers.
> - change "st,stm32-gptimer" compatible to "st,stm32-timers".
> - modify "st,breakinput" parameter in pwm part.
> - split DT patch in 2
> 
> version 5:
> - fix comments done on version 4
> - rebased on kernel 4.9-rc8
> - change nodes names and re-order then by addresses
> 
> version 4:
> - fix comments done on version 3
> - don't use interrupts anymore in IIO timer
> - detect hardware capabilities at probe time to simplify binding
> 
> version 3:
> - no change on mfd and pwm divers patches
> - add cross reference between bindings
> - change compatible to "st,stm32-timer-trigger"
> - fix attributes access rights
> - use string instead of int for master_mode and slave_mode
> - document device attributes in sysfs-bus-iio-timer-stm32
> - update DT with the new compatible
> 
> version 2:
> - keep only one compatible per driver
> - use DT parameters to describe hardware block configuration:
>   - pwm channels, complementary output, counter size, break input
>   - triggers accepted and create by IIO timers
> - change DT to limite use of reference to the node
> - interrupt is now in IIO timer driver
> - rename stm32-mfd-timer to stm32-timers (for general purpose timer)
> 
> The following patches enable PWM and IIO Timer features for STM32 platforms.
> 
> Those two features are mixed into the registers of the same hardware block
> (named general purpose timer) which lead to introduce a multifunctions driver 
> on the top of them to be able to share the registers.
> 
> In STM32f4 14 instances of timer hardware block exist, even if they all have
> the same register mapping they could have a different number of pwm channels
> and/or different triggers capabilities. We use various parameters in DT to 
> describe the differences between hardware blocks
> 
> The MFD (stm32-timers.c) takes care of clock and register mapping
> by using regmap. stm32_timers structure is provided to its sub-node to
> share those information.
> 
> PWM driver is implemented into pwm-stm32.c. Depending of the instance we may
> have up to 4 channels, sometime with complementary outputs or 32 bits counter
> instead of 16 bits. Some hardware blocks may also have a break input function
> which allows to stop pwm depending of a level, defined in devicetree, on an
> external pin.
> 
> IIO timer driver (stm32-timer-trigger.c and stm32-timer-trigger.h) define a list
> of hardware triggers usable by hardware blocks like ADC, DAC or other timers. 
> 
> The matrix of possible connections between blocks is quite complex so we use 
> trigger names and is_stm32_iio_timer_trigger() function to be sure that
> triggers are valid and configure the IPs.
> 
> At run time IIO timer hardware blocks can configure (through "master_mode" 
> IIO device attribute) which internal signal (counter enable, reset,
> comparison block, etc...) is used to generate the trigger.
> 
> By using "slave_mode" IIO device attribute timer can also configure on which
> event (level, rising edge) of the block is enabled.
> 
> Since we can use trigger from one hardware to control an other block, we can
> use a pwm to control an other one. The following example shows how to configure
> pwm1 and pwm3 to make pwm3 generate pulse only when pwm1 pulse level is high.
> 
> /sys/bus/iio/devices # ls
> iio:device0  iio:device1  trigger0     trigger1
> 
> configure timer1 to use pwm1 channel 0 as output trigger
> /sys/bus/iio/devices # echo 'OC1REF' > iio\:device0/master_mode
> configure timer3 to enable only when input is high
> /sys/bus/iio/devices # echo 'gated' > iio\:device1/slave_mode
> /sys/bus/iio/devices # cat trigger0/name
> tim1_trgo
> configure timer2 to use timer1 trigger is input
> /sys/bus/iio/devices # echo "tim1_trgo" > iio\:device1/trigger/current_trigger
> 
> configure pwm3 channel 0 to generate a signal with a period of 100ms and a
> duty cycle of 50%
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 0 > export
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 100000000 > pwm0/period
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 50000000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 1 > pwm0/enable
> here pwm3 channel 0, as expected, doesn't start because has to be triggered by
> pwm1 channel 0
> 
> configure pwm1 channel 0 to generate a signal with a period of 1s and a
> duty cycle of 50%
> /sys/devices/platform/soc/40010000.timers/40010000.timers:pwm/pwm/pwmchip0 # echo 0 > export
> /sys/devices/platform/soc/40010000.timers/40010000.timers:pwm/pwm/pwmchip0 # echo 1000000000 > pwm0/period
> /sys/devices/platform/soc/40010000.timers/40010000.timers:pwm/pwm/pwmchip0 # echo 500000000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40010000.timers/40010000.timers:pwm/pwm/pwmchip0 # echo 1 > pwm0/enable 
> finally pwm1 starts and pwm3 only generates pulse when pwm1 signal is high
> 
> An other example to use a timer as source of clock for another device.
> Here timer1 is used a source clock for pwm3:
> 
> /sys/bus/iio/devices # echo 100000 > trigger0/sampling_frequency 
> /sys/bus/iio/devices # echo "tim1_trgo" > iio\:device1/trigger/current_trigger 
> /sys/bus/iio/devices # echo 'external_clock' > iio\:device1/slave_mode
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 0 > export 
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 1000000 > pwm0/period 
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 500000 > pwm0/duty_cycle 
> /sys/devices/platform/soc/40000400.timers/40000400.timers:pwm/pwm/pwmchip4 # echo 1 > pwm0/enable
> 
> Benjamin Gaignard (8):
>   MFD: add bindings for STM32 Timers driver
>   MFD: add STM32 Timers driver
>   PWM: add pwm-stm32 DT bindings
>   PWM: add PWM driver for STM32 plaftorm
>   IIO: add bindings for STM32 timer trigger driver
>   IIO: add STM32 timer trigger driver
>   ARM: dts: stm32: add Timers driver for stm32f429 MCU
>   ARM: dts: stm32: Enable pw1 and pwm3 for stm32f469-disco
> 
>  .../ABI/testing/sysfs-bus-iio-timer-stm32          |  55 +++
>  .../bindings/iio/timer/stm32-timer-trigger.txt     |  23 +
>  .../devicetree/bindings/mfd/stm32-timers.txt       |  46 ++
>  .../devicetree/bindings/pwm/pwm-stm32.txt          |  33 ++
>  arch/arm/boot/dts/stm32f429.dtsi                   | 275 ++++++++++++
>  arch/arm/boot/dts/stm32f469-disco.dts              |  28 ++
>  drivers/iio/Kconfig                                |   2 +-
>  drivers/iio/Makefile                               |   1 +
>  drivers/iio/timer/Kconfig                          |  13 +
>  drivers/iio/timer/Makefile                         |   1 +
>  drivers/iio/timer/stm32-timer-trigger.c            | 466 +++++++++++++++++++++
>  drivers/iio/trigger/Kconfig                        |   1 -
>  drivers/mfd/Kconfig                                |  11 +
>  drivers/mfd/Makefile                               |   2 +
>  drivers/mfd/stm32-timers.c                         |  80 ++++
>  drivers/pwm/Kconfig                                |   9 +
>  drivers/pwm/Makefile                               |   1 +
>  drivers/pwm/pwm-stm32.c                            | 434 +++++++++++++++++++
>  include/linux/iio/timer/stm32-timer-trigger.h      |  62 +++
>  include/linux/mfd/stm32-timers.h                   |  71 ++++
>  20 files changed, 1612 insertions(+), 2 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>  create mode 100644 Documentation/devicetree/bindings/iio/timer/stm32-timer-trigger.txt
>  create mode 100644 Documentation/devicetree/bindings/mfd/stm32-timers.txt
>  create mode 100644 Documentation/devicetree/bindings/pwm/pwm-stm32.txt
>  create mode 100644 drivers/iio/timer/Kconfig
>  create mode 100644 drivers/iio/timer/Makefile
>  create mode 100644 drivers/iio/timer/stm32-timer-trigger.c
>  create mode 100644 drivers/mfd/stm32-timers.c
>  create mode 100644 drivers/pwm/pwm-stm32.c
>  create mode 100644 include/linux/iio/timer/stm32-timer-trigger.h
>  create mode 100644 include/linux/mfd/stm32-timers.h

This has really come together nicely.

Great work Benjamin.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
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