The aim of this series is to add support to the fan found on RPi's PoE HAT. Some commentary on the design can be found below. But the imporant part to the people CC'd here not involved with PWM is that, in order to achieve this properly, we also have to fix the firmware interface the driver uses to communicate with the PWM bus (and many other low level functions). Specifically, we have to make sure the firmware interface isn't unbound while consumers are still up. So, patch #1 introduces reference counting in the firwmware interface driver and patches #2 to #7 update all firmware users. Patches #8 to #10 introduce the new PWM driver.
I sent everything as a single series as the final version of the PWM drivers depends on the firwmare fixes, but I'll be happy to split this into two separate series if you think it's better. --- Original cover letter below --- This series aims at adding support to RPi's official PoE HAT fan[1]. The HW setup is the following: | Raspberry Pi | PoE HAT | arm core -> Mailbox -> RPi co-processor -> I2C -> Atmel MCU -> PWM -> FAN The arm cores have only access to the mailbox interface, as i2c0, even if physically accessible, is to be used solely by the co-processor (VideoCore 4/6). This series implements a PWM bus, and has pwm-fan sitting on top of it as per this discussion: https://lkml.org/lkml/2018/9/2/486. Although this design has a series of shortcomings: - It depends on a DT binding: it's not flexible if a new hat shows up with new functionality, we're not 100% sure we'll be able to expand it without breaking backwards compatibility. But without it we can't make use of DT thermal-zones, which IMO is overkill. - We're using pwm-fan, writing a hwmon driver would, again, give us more flexibility, but it's not really needed at the moment. I personally think that it's not worth the effort, it's unlikely we'll get things right in advance. And ultimately, if the RPi people come up with something new, we can always write a new driver/bindings from scratch (as in not reusing previous code). That said, I'm more than happy to change things if there is a consensus that another design will do the trick. [1] https://www.raspberrypi.org/blog/introducing-power-over-ethernet-poe-hat/ --- Changes since v1: - Address PWM driver changes - Fix binding, now with 2 cells - Add reference count to rpi_firmware_get() Nicolas Saenz Julienne (10): firmware: raspberrypi: Introduce rpi_firmware_put() clk: bcm: rpi: Release firmware handle on unbind gpio: raspberrypi-exp: Release firmware handle on unbind reset: raspberrypi: Release firmware handle on unbind soc: bcm: raspberrypi-power: Release firmware handle on unbind staging: vchiq: Release firmware handle on unbind input: raspberrypi-ts: Release firmware handle when not needed dt-bindings: pwm: Add binding for RPi firmware PWM bus DO NOT MERGE: ARM: dts: Add RPi's official PoE hat support pwm: Add Raspberry Pi Firmware based PWM bus .../arm/bcm/raspberrypi,bcm2835-firmware.yaml | 20 ++ arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 54 +++++ drivers/clk/bcm/clk-raspberrypi.c | 1 + drivers/firmware/raspberrypi.c | 30 ++- drivers/gpio/gpio-raspberrypi-exp.c | 14 +- drivers/input/touchscreen/raspberrypi-ts.c | 1 + drivers/pwm/Kconfig | 9 + drivers/pwm/Makefile | 1 + drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++ drivers/reset/reset-raspberrypi.c | 13 +- drivers/soc/bcm/raspberrypi-power.c | 15 ++ .../interface/vchiq_arm/vchiq_arm.c | 3 + .../pwm/raspberrypi,firmware-pwm.h | 13 ++ include/soc/bcm2835/raspberrypi-firmware.h | 3 + 14 files changed, 395 insertions(+), 3 deletions(-) create mode 100644 drivers/pwm/pwm-raspberrypi.c create mode 100644 include/dt-bindings/pwm/raspberrypi,firmware-pwm.h -- 2.28.0 _______________________________________________ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
