Confirmed PCIe bug in Kernel 4.0 (Kirkwood)

[sakaki]

Hello,

if you have a PCIe device on your Kirkwood system, that has stopped working after an upgrade to kernel 4.0, you may like to know that there is a known bug in the current 4.0 kernel (which therefore affects e.g. linux-kirkwood-dt 4.0-1).

The bug was introduced by commit a0b5cd4, and has been addressed by this patch, which is working its way through the usual pipeline towards release.

For those interested, the patch comment reads:$this->bbcode_second_pass_code('', 'Commit a0b5cd4ac2d6 ("bus: mvebu-mbus: use automatic I/O
synchronization barriers") enabled the usage of automatic I/O
synchronization barriers by enabling bit WIN_CTRL_SYNCBARRIER in the
control registers of MBus windows, but on non io-coherent platforms
(orion5x, kirkwood and dove) the WIN_CTRL_SYNCBARRIER bit in
the window control register is either reserved (all windows except 6
and 7) or enables read-only protection (windows 6 and 7).')
Hope that saves somebody else the fun of doing a kernel bisect ^-^

Best,

sakaki

[moonman]

sakaki, thank you for figuring this one out. Will commit the patch shortly.