On 04/21/2016 06:08 AM, Tomasz Nowicki wrote: > On 21.04.2016 11:36, Arnd Bergmann wrote: >> On Thursday 21 April 2016 11:28:15 Tomasz Nowicki wrote: >>> On 19.04.2016 15:06, Arnd Bergmann wrote: >>>> On Monday 18 April 2016 21:31:54 Tomasz Nowicki wrote: >>>>> >>>>> Basically the whole content of pci-thunder-ecam.c and >>>>> pci-thunder-pem.c. >>>>> >>>>> pci-thunder-ecam.c contains config space accessors. Similar for >>>>> pci-thunder-pem.c but it also has extra init call (it is now called >>>>> thunder_pem_init) which finds and maps related registers. >>>> >>>> They seem to do much more than just override the accessors, they >>>> actually >>>> change the contents of the config space as well. Is that really >>>> necessary >>>> on ACPI based systems as well? >>> >>> Yes, the pci-thunder-ecam.c accessors are meant to emulate config space >>> capabilities. They are necessary to synthesize EA capabilities (fixed >>> PCI BARs), it wont work without this, for ACPI boot as well. >> >> Why is that? I thought the BARs never get reassigned when using ACPI, >> so I'm surprised it's actually needed. Maybe I misunderstood what >> you mean by fixed PCI BARs. > > Yes, I meant something else. ThunderX has non-programmable PCI BAR > addresses. So it uses PCI EA (Extended allocation) capabilities to get > know PCI BARs addresses. But the early implementation (pass1.x) misses > EA capabilities hence we need to emulate it in config space accessors. Aside: In case it's helpful, at least one enterprise vendor I know of is only supporting later silicon as a result of this. So IMO there's no need to worry about this issue on the early preproduction chips. -- Computer Architect | Sent from my Fedora powered laptop -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
