Message Signaled Interrupt (MSI) for x64

NTDEV
1

I’m writing a wdf driver for a Genum/Semtech GN4124 PCIe interface chip.

So far the driver is working correctly and stable, incl. Interrupts and DMA.

Now I like to use message signaled interrupts instead of legacy INTA messages.
I made the entries in the inf file for enabling MSI and the MSI interrupts are working correctly under Windows 7, 32 Bit but under 64 Bit (Win 7 or Win 8.1) my ISR function get not called. Is there something special to care about in 64 Bit systems?

After loading the driver, I can check the config space and see the following MSI register are set:
MSI Control: 0081 8505
MSI Address: 0000 0000 FEEF F00C
MSI Data : 0000 0172

I also checked with a PCIe anaylzer if the MSI write command is send out and could not found any issue so far. I see a MWr(32) to address FEEF F00C with the data 0170.

Regards Roman

2

Does your device take 64 bit MSI address?

3

It should take 64 bit addresses. The 64 Bit MSI capability bit is set by the device and there is a 64 bit MSI address register.

4

Do you have another MSI capable device? What do you see in its descriptor?

5

The USB3 controller has MSI enabled too and the register are:

MSI Control: 00B7 0005
MSI Address: 0000 0000 FEEF F00C
MSI Data : 0000 01B8

If I compare it to my device the registers are set correctly.

6

The descriptor shows data 0172, and you see the message with data 0170. Why?

7

That was the problem, the GN4124 chip changes the data vector - dependend on the interrupt source and so the OS will not recognize the message any more.

The problem and solution is described here:

http://blog.tftechpages.com/?p=595

8

Wow… That’s a pretty crazy problem.

Good to know about, as more people migrate their legacy designs to PCIe (I understand the GN4124 can be pretty cost-effective in this role).

Thanks for posting the follow-up,

Peter
OSR
@OSRDrivers