On Tue, Aug 20, 2019 at 09:17:17AM -0500, Bjorn Helgaas wrote: > On Tue, Aug 20, 2019 at 12:58:20PM +0300, Mika Westerberg wrote: > > On Mon, Aug 19, 2019 at 06:52:45PM -0500, Bjorn Helgaas wrote: > > > > Right, it looks like we need some sort of flag there anyway. > > > > > > Does this mean you're looking at getting rid of "has_secondary_link", > > > you think it's impossible, or you think it's not worth trying? > > > > I was of thinking that we need some flag anyway for the downstream port > > (such as has_secondary_link) that tells us the which side of the port > > the link is. > > > > > I'm pretty sure we could get rid of it by looking upstream, but I > > > haven't actually tried it. > > > > So if we are downstream port, look at the parent and if it is also > > downstream port (or root port) we change the type to upstream port > > accordingly? That might work. > > If we see a type of PCI_EXP_TYPE_ROOT_PORT or > PCI_EXP_TYPE_PCIE_BRIDGE, I think we have to assume that's accurate > (which we already do today -- for those types, we assume the device > has a secondary link). > > For a device that claims to be PCI_EXP_TYPE_DOWNSTREAM, if a parent > device exists and is a Downstream Port (Root Port, Switch Downstream > Port, and I suppose a PCI-to-PCIe bridge (this is basically > pcie_downstream_port()), this device must actually be acting as a > PCI_EXP_TYPE_UPSTREAM device. > > If a device claiming to be PCI_EXP_TYPE_UPSTREAM has a parent that is > PCI_EXP_TYPE_UPSTREAM, this device must actually be a > PCI_EXP_TYPE_DOWNSTREAM port. > > For PCI_EXP_TYPE_DOWNSTREAM and PCI_EXP_TYPE_UPSTREAM devices that > don't have parents, we just have to assume they advertise the correct > type (as we do today). There are sparc and virtualization configs > like this. OK, thanks for the details. I'll try to make patch based on the above. > > Another option may be to just add a quirk for these ports. > > I don't really like the quirk approach because then we have to rely on > user reports of something being broken. > > > Only concern for both is that we have functions that rely on the type > > such as pcie_capability_read_word() so if we change the type do we end > > up breaking something? I did not check too closely, though. > > I don't think we'll break anything that's not already broken because > the type will reflect exactly what has_secondary_link now tells us. > In fact, we might *fix* some things, e.g., pcie_capability_read_word() > should work better if we fix the type that pcie_downstream_port() > checks. Fair enough :)
