Why does the HPS SPI Master fail when slave select is mapped to GPIO?

Description

Due to a problem with the SPI IP linux driver (spi-dw.c) in linux-socfpga kernel 4.1.22-ltsi, the SPI IP will fail to operate if slave select is routed to GPIO with the cs-gpios entry in device tree.

Resolution

This problem is fixed in the linux-socfpga-linux kernel 4.1.33-ltsi. 

GIT location:

https://github.com/altera-opensource/linux-socfpga

Precompiled version on Rocketboards.org:

https://rocketboards.org/foswiki/Documentation/GSRD170ReleaseNotes