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? Regards, Bjorn A > I'm not sure about link-up interrupt. I've just lightly tested using > PCIe HP on this port, getting no interrupts from it. > If I manually rescan the bus after enabling the qca6390 device (e.g. > via sysfs), it gets enabled, but then I see PCIe link errors (most > probably because the PCIe link was not retrained after the device > comes up). > > > Nit: when changing any file, please take a look at the commit history > > and make yours match, e.g., > > > > pcie-qcom: provide a way to power up qca6390 chip on RB5 platform > > > > does not look like: > > Ack. > > > -- > With best wishes > Dmitry
