On Fri, Aug 06, 2021 at 09:55:27PM -0500, Jeremy Linton wrote: > Hi, > > On 8/6/21 5:21 PM, Bjorn Helgaas wrote: > > On Thu, Aug 05, 2021 at 04:11:59PM -0500, Jeremy Linton wrote: > > > The PFTF CM4 is an ACPI platform that is following the PCIe SMCCC > > > standard because its PCIe config space isn't ECAM compliant and is > > > split into two parts. One part for the root port registers and a > > > moveable window which points at a given device's 4K config space. > > > Thus it doesn't have a MCFG (and really any MCFG provided would be > > > nonsense anyway). As Linux doesn't support the PCIe SMCCC standard > > > we key off a Linux specific host bridge _DSD to add custom ECAM > > > ops and cfgres. The cfg op selects between those two regions, as > > > well as disallowing problematic accesses, particularly if the link > > > is down because there isn't an attached device. > > > > I'm not sure SMCCC is *really* relevant here. If it is, an expansion > > of the acronym and a link to a spec would be helpful. > > > > But AFAICT the only important thing here is that it doesn't have > > standard ECAM, and we're going to work around that. > > I will reword it a bit. > > > I don't see anything about _DSD in this series. > > That is the "linux,pci-quirk" in the next patch. The next patch doesn't mention _DSD either. Is it obfuscated by being inside fwnode_property_read_string()? If so, it's well and truly hidden; I gave up trying to connect that with ACPI. Bjorn
