Hubert On 3/1/19 4:05 PM, Hubert Denkmair wrote: > Hello Dan, > >> +Required properties: > [...] >> + - device-wake-gpios: Wake up GPIO to wake up the TCAN device. >> + - device-state-gpios: Input GPIO that indicates if the device is in >> + a sleep state or if the device is active. > > If I understand the driver code correctly, device-wake-gpios and device-state-gpios are optional properties, not required? > OK I checked with the HW guy. The device-wake gpio is required and the device state is optional. Data sheet was not really clear on whether these are needed or not. Now it is just not this direct through. Setting bit 32:31 to disabled would remove the wake behavior, but it is not recommended This is because if the device is powered but does not get configured within 4 minutes of power up, it will put itself to sleep, and would never wake up without a POR/power cycle. So this may be an issue when doing suspend/resume if the power is removed or if the device is placed in reset. So I should probably update the wake gpio to required and fail probe if not found. > I'm currently designing a 4xTCAN4550 raspi hat, would be good to know whether a wake circuit is a must or not, > and how the device-state-gpios should be fed, if really needed. > Device state just signals the processor if the device is sleeping or not. If it is sleeping while trying to communicate the driver will wake up the device. Otherwise if the device state gpio is not available the wake pin is toggled everytime. > Cheers, > > Hubert > -- ------------------ Dan Murphy
