unable to set value of latency_timer register of PCI configuration space

Question

I am trying to set latency timer value of my Intel PCI card using following command

sudo setpci -d '8086:0100' latency_timer=01

But when I read the value of this register back it is unchanged and shows previous value.

I am using following command to display value of the register

sudo setpci -d '8086:0100' latency_timer

Can anybody tell why I'm unable to change value of latency timer?

I'm using a Linux machine.

Answer 1

There is a good chance that you have more than one PCI devices or more than one functions with identical vid:did.

Find out the location of your PCI device using sudo lspci, then use

sudo setpci -s bus:slot.func ...

instead of

sudo setpci -d vid:did ...