Re: [PATCH v3 0/7] Add pwm and IIO timer drivers for stm32

[Jonathan Cameron]

On 02/12/16 10:17, Benjamin Gaignard wrote:
> 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
> - udpate 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-gptimer (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 stm32 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-gptimer.c) takes care of clock and register mapping
> by using regmap. stm32_gptimer_dev 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-iio-timer.c and stm32-iio-timers.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.
> Possible triggers ar listed in include/dt-bindings/iio/timer/st,stm32-iio-timer.h
> 
> 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.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 0 > export
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 100000000 > pwm0/period
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 50000000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@0/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.gptimer1/40010000.gptimer1:pwm1@0/pwm/pwmchip0 # echo 0 > export
> /sys/devices/platform/soc/40010000.gptimer1/40010000.gptimer1:pwm1@0/pwm/pwmchip0 # echo 1000000000 > pwm0/period
> /sys/devices/platform/soc/40010000.gptimer1/40010000.gptimer1:pwm1@0/pwm/pwmchip0 # echo 500000000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40010000.gptimer1/40010000.gptimer1:pwm1@0/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.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 0 > export 
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 1000000 > pwm0/period 
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 500000 > pwm0/duty_cycle 
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@0/pwm/pwmchip4 # echo 1 > pwm0/enable 
This is good thorough documentation.  Could we have an additional
patch adding just this documentation to the tree (probably under
Documentation/mfd?). Documentation in general is a bit in flux at the
moment so we'll may want to sphixify it afterwards but plain text
is fine for now.

Jonathan


> 
> Benjamin Gaignard (7):
>   MFD: add bindings for stm32 general purpose timer driver
>   MFD: add stm32 general purpose timer 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 stm32 general purpose timer driver in DT
> 
>  .../ABI/testing/sysfs-bus-iio-timer-stm32          |  47 ++
>  .../bindings/iio/timer/stm32-timer-trigger.txt     |  39 ++
>  .../bindings/mfd/stm32-general-purpose-timer.txt   |  47 ++
>  .../devicetree/bindings/pwm/pwm-stm32.txt          |  38 ++
>  arch/arm/boot/dts/stm32f429.dtsi                   | 333 +++++++++++++-
>  arch/arm/boot/dts/stm32f469-disco.dts              |  28 ++
>  drivers/iio/Kconfig                                |   2 +-
>  drivers/iio/Makefile                               |   1 +
>  drivers/iio/timer/Kconfig                          |  15 +
>  drivers/iio/timer/Makefile                         |   1 +
>  drivers/iio/timer/stm32-timer-trigger.c            | 477 +++++++++++++++++++++
>  drivers/iio/trigger/Kconfig                        |   1 -
>  drivers/mfd/Kconfig                                |  10 +
>  drivers/mfd/Makefile                               |   2 +
>  drivers/mfd/stm32-gptimer.c                        |  73 ++++
>  drivers/pwm/Kconfig                                |   8 +
>  drivers/pwm/Makefile                               |   1 +
>  drivers/pwm/pwm-stm32.c                            | 285 ++++++++++++
>  .../iio/timer/st,stm32-timer-triggers.h            |  60 +++
>  include/linux/iio/timer/stm32-timer-trigger.h      |  16 +
>  include/linux/mfd/stm32-gptimer.h                  |  62 +++
>  21 files changed, 1543 insertions(+), 3 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-general-purpose-timer.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-gptimer.c
>  create mode 100644 drivers/pwm/pwm-stm32.c
>  create mode 100644 include/dt-bindings/iio/timer/st,stm32-timer-triggers.h
>  create mode 100644 include/linux/iio/timer/stm32-timer-trigger.h
>  create mode 100644 include/linux/mfd/stm32-gptimer.h
>