I am seeing a very strange problem with the jsm driver.
I am using a Digi Neo 2 DB9 card on a system with a Geode SC1200 cpu.
This is essentially an EXAR XC17D152 chip rebranded for Digi.
Kernel is based on debian's 2.6.16-17 which is 2.6.16.25 with a few
patches.
When I use minicom to transmit a chunk of text by sending a text file,
the data is transmitted in the wrong order.
testfile:
0123456789ABCDEF
Received text:
123056749AB8DEFC
If I use the same driver and the same card on a P4 system, everything
works fine.
The driver is doing memcpy_toio to tranfer data to the transmit FIFO
(which is a 64byte memory mapped block of memory on the PCI bus as far
as I can tell). The data in the transmit queue is in the right order
being passed to memcpy_toio, but somehow by the time it is in the uart
and goes out the transmiter, every 4th byte is moved 3 bytes back.
Transmitting a single character at a time works fine of course since
there is nothing to swap it around with, and it is only copying a single
byte to the UART rather than a block of bytes.
I read something about the geodes doing memory write reordering, but
that it is supposed to magically not screw up PCI writes. I have no
idea if it is or not though.
I have no problem with pcnet32 or any of the other PCI devices I use.
Does anyone have any suggestions for something to try?
The cpu in question has this information:
processor : 0
vendor_id : CyrixInstead
cpu family : 5
model : 9
model name : Unknown
stepping : 1
cpu MHz : 266.760
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu tsc msr cx8 cmov mmx cxmmx
bogomips : 535.33
I noticed that cyrix.c has some code for controlling reordering and
such, although it doesn't seem to match this particular cpu's ID, so it
isn't called. I have no idea if it should have.
--
Len Sorensen
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