On 10/14/2017 06:13 AM, Benjamin Herrenschmidt wrote: > No, he's saying this is useful for the developers when debugging the > kernel driver (or for asking users to "test" something as part of > debugging a driver problem). > > It's common to have various command line options affecting PCIe > behaviour. I don't see a fundamental problem with this one.
Thanks Ben, very well explained. > > One could argue in fact that we should always PERST everything, the > main reason for not doing so is that on "normal" boot, OPAL has already > done it and it would slow the boot process down. > > My only objection here is the actual name of the argument. We've had a > number of pci options so far, it makes sense to make sure we still have > "pci" in the name. I just wanted to take advantage of the already existing argument, reset_devices. And..in fact, the PERST is a reset right? But if you prefer, we can change it - pci_force_reset? Suggestions are welcome. > > Also having the driver do a "reset" is not always simple, we don't > always have full control of PERST on a per-device basis. The patch > proposed will PERST top level PHBs which will propagate as hot reset > down switches, not 100% PERST but still useful. > Exactly, this reset happens on early arch stage of PCI initialization, not trivial to drivers perform it. Anyway, let me know if you want a V2 with improvements or to drop it..I still see use cases for this. Thanks, Guilherme > Cheers, > Ben. >
