On 11/2/20 7:57 PM, Thomas.Kopp@microchip.com wrote:
>> It may be a blunt guess, but according to page 99
>>
>> https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm27
>> 11/rpi_DATA_2711_1p0.pdf
>>
>> Pin 26 is pulldown. So it works if it remains unused because the pin is
>> input with pulldown thus the chip is selected by default.
>>
>> I don't know if the CE pin can actually work if there is no matching alt
>> function in pinselect register.

> Do you suggest that the communication works with a permanent low on CS/CE?

No.

> Without the CS/CE pin having edges you will not be able to send multiple 
> commands. The driver is writing/reading multiple times when bringing up the
> chip. If you have a permanent low that will fail. So somehow the CS does 
> generate the right edges.

The overlay configures the Pin for gpio and the SPI driver uses it in GPIO mode.

Marc

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