* Jan Kiszka <[email protected]> [2018-01-24 07:12:37 +0100]: [...]
> >> > >> - use FLR where available > >> - warn if it's not > >> - unconditionally clear the command register and try to set INTx-off > > > > OK. Naming them 1, 2 and 3, I just can't do 3 when FLR is not > > available: it is an unsupported request. > > > > The command register is present in every PCI device. Therefore, 3 is > independent of FLR or PCIe support. OK, back to (more) testing mode on this front, hold on and I'll come back with something, I hope. [...] > > Do you mean PIO instructions? We're looking at accesses to > > PCI_CAP_PCIE | JAILHOUSE_PCI_EXT_CAP cap, that can only live on the > > mmio space, no? So we got pristine loads and stores, thus the "normal" > > cycle count. I'll assume that cycle amount and use current CPU freq. > > as an estimate, I guess. > > Memory mapped I/O can delay the triggering instruction if the device is > not confirming the transaction / delivering the data requested on read. > You will not measure cache speed here when you try define the loop delay > - believe me, or better try it out. OK, my bad ignoring stalls on those MMIO-mapped accesses, you're right. I just don't buy the "find some constants that get near 100ms for *some CPU/chipset/PCI device* you judge modern enough" and make that the default cycle count. How is that any better than my approach of guaranteeing *at least* 100ms on modern IA CPUs (any extra coming from PCI access delays), being that the spec allows for > 100ms waits and that would work for a lot more people without even having to tune? My next commit would derive the CPU frequency from /sys and we'd have sane values for everyone automatically. > > Jan > > -- > Siemens AG, Corporate Technology, CT RDA IOT SES-DE > Corporate Competence Center Embedded Linux > > -- > You received this message because you are subscribed to the Google Groups > "Jailhouse" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- Gustavo Lima Chaves Intel - Open Source Technology Center -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
