On Sat 30 Jan 10:14 CST 2021, Dmitry Baryshkov wrote: > On Sat, 30 Jan 2021 at 06:53, Bjorn Andersson > <bjorn.andersson@xxxxxxxxxx> wrote: > > > > On Fri 29 Jan 16:19 CST 2021, Dmitry Baryshkov wrote: > > > > > On Sat, 30 Jan 2021 at 00:50, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > > > > > > On Fri, Jan 29, 2021 at 06:45:21AM +0300, Dmitry Baryshkov wrote: > > > > > On 28/01/2021 22:26, Rob Herring wrote: > > > > > > On Thu, Jan 28, 2021 at 11:52 AM Dmitry Baryshkov > > > > > > <dmitry.baryshkov@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > Some Qualcomm platforms require to power up an external device before > > > > > > > probing the PCI bus. E.g. on RB5 platform the QCA6390 WiFi/BT chip needs > > > > > > > to be powered up before PCIe0 bus is probed. Add a quirk to the > > > > > > > respective PCIe root bridge to attach to the power domain if one is > > > > > > > required, so that the QCA chip is started before scanning the PCIe bus. > > > > > > > > > > > > This is solving a generic problem in a specific driver. It needs to be > > > > > > solved for any PCI host and any device. > > > > > > > > > > Ack. I see your point here. > > > > > > > > > > As this would require porting code from powerpc/spark of-pci code and > > > > > changing pcie port driver to apply power supply before bus probing happens, > > > > > I'd also ask for the comments from PCI maintainers. Will that solution be > > > > > acceptable to you? > > > > > > > > I can't say without seeing the code. I don't know enough about this > > > > scenario to envision how it might look. > > > > > > > > I guess the QCA6390 is a PCIe device? Why does it need to be powered > > > > up before probing? Shouldn't we get a link-up interrupt when it is > > > > powered up so we could probe it then? > > > > > > Not quite. QCA6390 is a multifunction device, with PCIe and serial > > > parts. It has internal power regulators which once enabled will > > > powerup the PCIe, serial and radio parts. There is no need to manage > > > regulators. Once enabled they will automatically handle device > > > suspend/resume, etc. > > > > > > > So what you're saying is that if either the PCI controller or bluetooth > > driver probes these regulators will be turned on, indefinitely? > > > > If so, why do we need a driver to turn them on, rather than just mark > > them as always-on? > > > > What's the timing requirement wrt regulators vs WL_EN/BT_EN? > > According to the documentation I have, they must be enabled right > after enabling powering the chip and they must stay enabled all the > time. > So presumably just marking these things always-on and flipping the GPIO statically won't be good enough due to the lack of control over the timing. This really do look like a simplified case of what we see with the PCIe attached modems, where similar requirements are provided, but also the ability to perform a device specific reset sequence in case the hardware has locked up. I'm slightly worried about the ability of extending your power-domain model to handle the restart operation though. Regards, Bjorn
