Hi, we have migrated from Dizzy (1.4.2) to Krogoth (2.1.1). The kernel version have changed from 3.8 to 4.1 and the SPI peripheral on Quark x1001 had a problem with enumeration. 2 SPIs were enumerated by spi-pxa2xx-pci driver as spi168.0 and and spi169.0. Because of that the spidev driver couldn't connect with these interfaces. The fix we made is pretty straightforward: http://pastebin.com/D7ZGfMYS . It covers the problem so the SPI is being detected correctly. The other thing is when SPI is connected to device (KSZ8795CLX switch) which requires 24bit continuous transmission without raising chip select the maximum speed we can achieve is 5MHz. In previous kernel version (3.8) it was working at 25MHz speed. The CS is raised up automatically after each 8bit sequence. The application code is exactly the same as in previous version - simplified part of read/write procedure: http://pastebin.com/tLTt836M . The CS pin is driven automatically when the FIFO is empty so I suppose that sending data through xfer structure is too slow. Do you have any idea how could I increase the SPI speed and also could you verify if the fix for SPI enumeration is sufficient and will not produce any negative effects?
Thank you for your reply in advance, Mateusz Orzoł --
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