AM625: SPI daisy chain

Hi Kuwahara-san,

Kei Kuwahara said:

Would AM625 support SPI daisy chain?

If so, is there any sample codes for using SPI daisy chain?

the hardware SPI module should support it, but we (TI) don't have any sample code for this. Doing a quick search online it looks like there was an attempt to upstream a SPI daisy chain driver that inserts itself between the SPI HW module, and the SPI (slave) device drivers, see:

[PATCH v2 1/2] spi: Add the SPI daisy chain support
https://www.uwsg.indiana.edu/hypermail/linux/kernel/2007.0/04967.html

[PATCH v2 2/2] dt-bindings: Add documentation for SPI daisy chain driver
https://www.uwsg.indiana.edu/hypermail/linux/kernel/2007.0/04968.html

You could probably extract the patches and apply them to the Kernel and with a little work bring it up and get it going.

As an alternative you could use the "spidev" driver in the Kernel, and manage everything from userspace, see https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/09_00_00_03/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/SPI.html?highlight=spidev. But then you would not be able to take advantage of the existing Linux Kernel SPI (slave) device drivers.

Regards, Andreas