Hi, On Thu, Jan 04, 2024 at 02:01:14PM +0100, Bartosz Golaszewski wrote: > During last year's Linux Plumbers we had several discussions centered > around the need to power-on PCI devices before they can be detected on > the bus. > > The consensus during the conference was that we need to introduce a > class of "PCI slot drivers" that would handle the power-sequencing. > > After some additional brain-storming with Manivannan and the realization > that the DT maintainers won't like adding any "fake" nodes not > representing actual devices, we decided to reuse the existing > infrastructure provided by the PCIe port drivers. > > The general idea is to instantiate platform devices for child nodes of > the PCIe port DT node. For those nodes for which a power-sequencing > driver exists, we bind it and let it probe. The driver then triggers a > rescan of the PCI bus with the aim of detecting the now powered-on > device. The device will consume the same DT node as the platform, > power-sequencing device. We use device links to make the latter become > the parent of the former. > > The main advantage of this approach is not modifying the existing DT in > any way and especially not adding any "fake" platform devices. I recently ran into this issue on a Rockchip platform using a PCIe based AP6275P WLAN device (broadcom based). As far as I can tell your proposal should also work for that one (obviously using a different pwrseq driver). -- Sebastian > Bartosz Golaszewski (9): > arm64: dts: qcom: sm8250: describe the PCIe port > arm64: dts: qcom: qrb5165-rb5: describe the WLAN module of QCA6390 > PCI/portdrv: create platform devices for child OF nodes > PCI: hold the rescan mutex when scanning for the first time > PCI/pwrseq: add pwrseq core code > dt-bindings: vendor-prefixes: add a PCI prefix for Qualcomm Atheros > dt-bindings: wireless: ath11k: describe QCA6390 > PCI/pwrseq: add a pwrseq driver for QCA6390 > arm64: defconfig: enable the PCIe power sequencing for QCA6390 > > .../net/wireless/qcom,ath11k-pci.yaml | 14 ++ > .../devicetree/bindings/vendor-prefixes.yaml | 1 + > arch/arm64/boot/dts/qcom/qrb5165-rb5.dts | 24 +++ > arch/arm64/boot/dts/qcom/sm8250.dtsi | 10 + > arch/arm64/configs/defconfig | 2 + > drivers/pci/pcie/Kconfig | 2 + > drivers/pci/pcie/Makefile | 2 + > drivers/pci/pcie/portdrv.c | 3 +- > drivers/pci/pcie/pwrseq/Kconfig | 19 ++ > drivers/pci/pcie/pwrseq/Makefile | 4 + > drivers/pci/pcie/pwrseq/pcie-pwrseq-qca6390.c | 197 ++++++++++++++++++ > drivers/pci/pcie/pwrseq/pwrseq.c | 83 ++++++++ > drivers/pci/probe.c | 2 + > include/linux/pcie-pwrseq.h | 24 +++ > 14 files changed, 386 insertions(+), 1 deletion(-) > create mode 100644 drivers/pci/pcie/pwrseq/Kconfig > create mode 100644 drivers/pci/pcie/pwrseq/Makefile > create mode 100644 drivers/pci/pcie/pwrseq/pcie-pwrseq-qca6390.c > create mode 100644 drivers/pci/pcie/pwrseq/pwrseq.c > create mode 100644 include/linux/pcie-pwrseq.h > > -- > 2.40.1 > >
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