Bjorn, Mika, On 25/06/18 15:01, Bjorn Helgaas wrote: > Hi Marc, > > Sorry we broke this! No worries, gave me a chance to stare at something else! ;-) > > On Thu, Jun 21, 2018 at 05:47:15PM +0100, Marc Zyngier wrote: >> Until recently, shpc_probe() would bail out pretty early in the >> absence of the SHPC capability. A logic change in the way the >> driver now checks that capability makes it go and probe the >> firmware anyway, with ugly consequences if the system is not >> ACPI based (my arm64 ThunderX is DT driven, and explodes in >> a spectacular way after getting a NULL root bridge from the >> non-existent ACPI tables...). >> >> Take this opportunity to move the call to shpchp_is_native() >> back into shpc_probe(), making it clear that a non-ACPI system >> is not expected to use this driver. > > But a non-ACPI system *should* be able to use SHPC. Yeah, I only realized that once Mika pointed it out. > Here's my understanding of how it should work. On an ACPI system, > > - If firmware has _OSC, the OS calls it to request permission to > manage the SHPC. If _OSC grants permission, it should also > configure the hardware (interrupts, etc) to give the OS. > > - If there's no _OSC, shpchp assumes it's allowed to manage the > SHPC, and it calls OSHP to configure the hardware appropriately. > > On a non-ACPI system, shpchp assumes there's no firmware involved at > all, so it can manage the SHPC without doing anything special. > > I see Mika has already posted a patch similar to the first one > below; I think either of those should fix the problem you're seeing. Absolutely. With this early exit when root is NULL, my test box is back up and running. > The second is an attempt to clean things up so they make a > little more sense. I haven't tried that second patch yet, but from reading it, it definitely helps making sense of this driver. Thanks, M. -- Jazz is not dead. It just smells funny...
