> Florian Fainelli <[email protected]> hat am 3. September 2018 um 20:31 > geschrieben: > > > > > On 9/2/2018 10:13 AM, Stefan Wahren wrote: > > Hi Guenter, > > > >> Guenter Roeck <[email protected]> hat am 2. September 2018 um 18:49 > >> geschrieben: > >> > >> > >> On 09/02/2018 09:26 AM, Stefan Wahren wrote: > >>> Hi Guenter, > >>> > >>>> Guenter Roeck <[email protected]> hat am 2. September 2018 um 16:23 > >>>> geschrieben: > >>>> > >>>> > >>>> On 09/02/2018 04:20 AM, Stefan Wahren wrote: > >>>>> This series is an early stage of the hwmon driver for the fan on the > >>>>> Raspberry Pi Power over Ethernet HAT [1]. At the end this should use a > >>>>> Device Tree Overlay. > >>>>> > >>>>> Changes by Stefan based on [2]: > >>>>> - reformat the downstream patches for submission > >>>>> - drop reboot notification > >>>>> - fix remaining checkpatch issues > >>>>> - add COMPILE_TEST to Kconfig > >>>>> > >>>>> The driver is mostly copy & paste from pwm-fan, which isn't good. > >>>>> Personally > >>>>> i see two options: > >>>>> > >>>>> 1) integrate the driver function into the pwm-fan driver (new > >>>>> compatible) > >>>>> 2) implement the core function as a PWM driver and use the pwm-fan > >>>>> driver on top > >>>>> > >>>> > >>>> I don't really see the point of thise driver. Why not implement either > >>>> of those ? > >>> > >>> i'm not sure about your question. Since the fan is placed over the SoC, > >>> the fan should takes care of the SoC temperature. AFAIK the firmware > >>> should have exclusive access to the I2C. So why we need this mailbox > >>> interface instead of a I2C driver. > >>> > >> > >> The driver sets pwm values. The pwm-fan driver sets pwm values. A pwm > >> driver > >> sets pwm values. The pwm-fan driver uses a pwm driver to set pwm values. > >> You appear to be arguing that the pwm-fan driver for Rpi is different than > >> a pwm-fan driver for all other hardware and should _not_ use a pwm driver > >> to set pwm values. > > > > thanks for your explanation. Now i think i understand and sorry for the > > confusion. We need a driver which translate the pwm values into the mailbox > > properties. "My" RFC series is only a starting point (not intended for > > merge and not an option) for a discussion and i'm perfectly fine with 2). > > Both options would be feasible in general. I only wanted to know your > > opinion before i start to implement one of them. > > Is not there a way to expose the PWM pins directly to the kernel instead > of going through the firmware to do that for us? I am just asking > because sometimes this appears to be possible, guess not in this case?
According to this blog entry (no schematics available so far) [1], this is my understanding of the fan control: | Raspberry Pi 3B+ | PoE HAT | ARM core -Mailbox-> VideoCore4 -I2C-> Atmel MCU -PWM-> FAN The only chance would be to bypass VC4 and talk to the Atmel microcontroller directly. But this would require a specification of the I2C protocol or some time of reverse engineering. Maybe the foundation guys can say something about that? [1] - https://www.raspberrypi.org/blog/introducing-power-over-ethernet-poe-hat/ > -- > Florian
