On Mon, Jul 18, 2022 at 6:40 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Mon, Jul 18, 2022 at 02:56:03PM -0400, Jim Quinlan wrote: > > On Mon, Jul 18, 2022 at 2:14 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > 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. > > > > Actually, what you describe is what I proposed with my v1 back in Nov 2020. > > The binding commit message said, > > > > "Quite similar to the regulator bindings found in > > "rockchip-pcie-host.txt", this allows optional regulators to be > > attached and controlled by the PCIe RC driver." > > > > > 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. > > > > The reviewer's requested me to move the regulator node(s) > > elsewhere, and at some point later it was requested to be placed > > under the Root Port driver. I would love to return them under the > > host bridge, just say the word! > > Actually, I think my understanding is wrong. Even though the PCI core > hasn't enumerated the Root Port as a pci_dev, brcm_pcie_setup() knows > about it and should be able to look up the regulators and turn them > on. One can do this with regulator_bulk_get(NULL, ...); However, MarkB did not like the idea of a driver getting the regulator from the global DT namespace [1]. For the RC driver, one cannot invoke regulator_bulk_get(dev, ...) if there is not a direct child regulator node. One needs to use the Port driver device. The Port driver device does not exist at this point unless one tries to prematurely create it; I tried this and it was a mess to say the least. > > Can you dig up the previous discussion about why the regulators need > to be under the Root Port and why they can't be turned on before > calling pci_host_probe()? RobH did not want the regulators to be under the RC as he said their DT location should resemble the HW [2]. The consensus evolved to place it under the port driver, which can provide a general mechanism for turning on regulators anywhere in the PCIe tree. Regards, Jim Quinlan Broadcom STB [1] https://lore.kernel.org/linux-pci/20210329162539.GG5166@xxxxxxxxxxxxx/ [2] https://lore.kernel.org/linux-pci/CAL_JsqKPKk3cPO8DG3FQVSHrKnO+Zed1R=PV7n7iAC+qJKgHcw@xxxxxxxxxxxxxx/ > > > Bjorn
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