[meta-intel] SPI enumeration and maximum speed on Intel Quark x1001 based platform when migrating from kernel 3.8 to 4.1.

[Mateusz Orzoł]

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
 --
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.yoctoproject.org/pipermail/meta-intel/attachments/20161222/6568d44c/attachment.html>