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Message-ID: <ad5bacf0-3836-dd3d-5d7c-cbd92b626618@kernel.org>
Date: Sat, 3 Dec 2016 09:32:42 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Benjamin Gaignard <benjamin.gaignard@...aro.org>,
lee.jones@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
alexandre.torgue@...com, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, thierry.reding@...il.com,
linux-pwm@...r.kernel.org, knaack.h@....de, lars@...afoo.de,
pmeerw@...erw.net, linux-iio@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Cc: fabrice.gasnier@...com, gerald.baeza@...com,
arnaud.pouliquen@...com, linus.walleij@...aro.org,
linaro-kernel@...ts.linaro.org,
Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH v3 0/7] Add pwm and IIO timer drivers for stm32
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@...wm/pwmchip4 # echo 0 > export
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@...wm/pwmchip4 # echo 100000000 > pwm0/period
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@...wm/pwmchip4 # echo 50000000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@...wm/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@...wm/pwmchip0 # echo 0 > export
> /sys/devices/platform/soc/40010000.gptimer1/40010000.gptimer1:pwm1@...wm/pwmchip0 # echo 1000000000 > pwm0/period
> /sys/devices/platform/soc/40010000.gptimer1/40010000.gptimer1:pwm1@...wm/pwmchip0 # echo 500000000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40010000.gptimer1/40010000.gptimer1:pwm1@...wm/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@...wm/pwmchip4 # echo 0 > export
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@...wm/pwmchip4 # echo 1000000 > pwm0/period
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@...wm/pwmchip4 # echo 500000 > pwm0/duty_cycle
> /sys/devices/platform/soc/40000400.gptimer3/40000400.gptimer3:pwm3@...wm/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
>
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