Hi All,
I wonder When and Why FLR,PCI Hot Reset and PERST resets are getting triggered in Real World. I could see multiple resets are defined in PCIe spec, Does this really happen ? if so, Could some one enlighten me with some real world use case?
How frequently these resets can come?
Thanks in advance,
Muthu
It’s depressing to see no replies here so I’d risk to take a shot.
Hot reset likely occurs every time you reboot a machine while it is powered on. PERST may be driven by the BIOS, if these lines are routed to the slots or slot-less devices.
FLR is quite complicated, as you may see in the spec. I haven’t seen using it yet, but PCIe IP used in project I’m working on now, has it.
PERST is the simplest, most robust way. From my (very limited) experience, PERST is popular in appliances such as modems, routers etc. In these devices PERST for PCIe slots usually is driven by custom GPIO pins and software can trigger it at will. (The OS in these things is not Windows, so, to keep the story short - there’s no blue screens, it Just Works, as one can expect from a humble appliance).
Regards,
– pa
Since there was no reply from any one, I thought it wasn’t correct forum for this question. Thank you very much for your reply.
Just would like to know, Does these reset comes in running PCs eg. Datacenters. If it comes, what would be the recovery mechanism followed. It will be very good, if some one gives real time case study.
Thanks and Regards,
Muthu
xxxxx@gmail.com wrote:
Just would like to know, Does these reset comes in running PCs eg. Datacenters. If it comes, what would be the recovery mechanism followed. It will be very good, if some one gives real time case study.
Well, remember that these signals always represent exception
conditions. Correctly running hardware in steady state should never see
or need a reset, and your driver should never see a reset that it wasn’t
expecting. They don’t just happen out of the blue. The system isn’t
going to suddenly decide “gee, I think I’ll reset the board in slot 6”.
Of course your hardware will be reset during a reboot process, but your
driver is going to be restarted.
The FLR is something that could be used on a normally operating machine,
I suppose, but it’s never going to be imposed on you. Your driver would
have to initiate it, and presumably it would know why it did so and how
to recover.
–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.