On Sat, Jul 16, 2022 at 06:24:49PM -0400, Jim Quinlan wrote: > Currently, the function does the setup for establishing PCIe link-up > with the downstream device, and it does the actual link-up as well. > The calling sequence is (roughly) the following in the probe: > > -> brcm_pcie_probe() > -> brcm_pcie_setup(); /* Set-up and link-up */ > -> pci_host_probe(bridge); > > This commit splits the setup function in two: brcm_pcie_setup(), which only > does the set-up, and brcm_pcie_start_link(), which only does the link-up. > The reason why we are doing this is to lay a foundation for subsequent > commits so that we can turn on any power regulators, as described in the > root port's DT node, prior to doing link-up. All drivers that care about power regulators turn them on before link-up, but typically those regulators are described directly under the host bridge itself. IIUC the difference here is that you have regulators described under Root Ports (not the host bridge/Root Complex itself), so you don't know about them until you've enumerated the Root Ports. brcm_pcie_probe() can't turn them on directly because it doesn't know what Root Ports are present and doesn't know about regulators below them. So I think brcm_pcie_setup() does initialization that doesn't depend on the link or any downstream devices, and brcm_pcie_start_link() does things that depend on the link being up. Right? If so, "start_link" might be a slight misnomer since AFAICT brcm_pcie_start_link() doesn't do anything to initiate link-up except maybe deasserting fundamental reset. Some drivers start the LTSSM or explicitly enable link training, but brcm_pcie_start_link() doesn't seem to do anything like that. brcm_pcie_start_link() still does brcm_pcie_set_outbound_win(). Does that really depend on the link being up? If that only affects the Root Port, maybe it could be done before link-up? > We do this by defining an > add_bus() callback which is invoked during enumeraion. At the end of this > patchset the probe function trace will look something like this: > > -> brcm_pcie_probe() > -> brcm_pcie_setup(); /* Set-up only */ > -> pci_host_probe(bridge); > -> [enumeration] > -> pci_alloc_child_bus() > -> bus->ops->add_bus(bus); /* We've set this op */ > -> brcm_pcie_add_bus() /* Our callback */ > -> [turn on regulators] /* Main objective! */ > -> brcm_pcie_start_link() /* Link-up */
