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[0/9] PCI: introduce the concept of power sequencing of PCIe devices

Message ID 20240117160748.37682-1-brgl@bgdev.pl
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Series PCI: introduce the concept of power sequencing of PCIe devices | expand

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Bartosz Golaszewski Jan. 17, 2024, 4:07 p.m. UTC 
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

The responses to the RFC were rather positive so here's a proper series.

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 DT maintainers won't like adding any "fake" nodes not representing
actual devices, we decided to reuse existing PCI infrastructure.

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.

Changes since RFC:
- move the pwrseq functionality out of the port driver and into PCI core
- add support for WCN7850 to the first pwrseq driver (and update bindings)
- describe the WLAN modules in sm8550-qrd and sm8650-qrd
- rework Kconfig options, drop the defconfig changes from the series as
  they are no longer needed
- drop the dt-binding changes for PCI vendor codes
- extend the DT bindings for ath11k_pci with strict property checking
- various minor tweaks and fixes

Bartosz Golaszewski (7):
  arm64: dts: qcom: qrb5165-rb5: describe the WLAN module of QCA6390
  PCI: create platform devices for child OF nodes of the port node
  PCI: hold the rescan mutex when scanning for the first time
  PCI/pwrseq: add pwrseq core code
  dt-bindings: wireless: ath11k: describe QCA6390
  dt-bindings: wireless: ath11k: describe WCN7850
  PCI/pwrseq: add a pwrseq driver for QCA6390

Neil Armstrong (2):
  arm64: dts: qcom: sm8550-qrd: add Wifi nodes
  arm64: dts: qcom: sm8650-qrd: add Wifi nodes

 .../net/wireless/qcom,ath11k-pci.yaml         |  89 ++++++
 arch/arm64/boot/dts/qcom/qrb5165-rb5.dts      |  29 ++
 arch/arm64/boot/dts/qcom/sm8250.dtsi          |  10 +
 arch/arm64/boot/dts/qcom/sm8550-qrd.dts       |  37 +++
 arch/arm64/boot/dts/qcom/sm8550.dtsi          |  10 +
 arch/arm64/boot/dts/qcom/sm8650-qrd.dts       |  29 ++
 arch/arm64/boot/dts/qcom/sm8650.dtsi          |  10 +
 drivers/pci/Kconfig                           |   1 +
 drivers/pci/Makefile                          |   1 +
 drivers/pci/bus.c                             |   9 +-
 drivers/pci/probe.c                           |   2 +
 drivers/pci/pwrseq/Kconfig                    |  16 ++
 drivers/pci/pwrseq/Makefile                   |   4 +
 drivers/pci/pwrseq/pci-pwrseq-qca6390.c       | 267 ++++++++++++++++++
 drivers/pci/pwrseq/pwrseq.c                   |  82 ++++++
 drivers/pci/remove.c                          |   3 +-
 include/linux/pci-pwrseq.h                    |  24 ++
 17 files changed, 621 insertions(+), 2 deletions(-)
 create mode 100644 drivers/pci/pwrseq/Kconfig
 create mode 100644 drivers/pci/pwrseq/Makefile
 create mode 100644 drivers/pci/pwrseq/pci-pwrseq-qca6390.c
 create mode 100644 drivers/pci/pwrseq/pwrseq.c
 create mode 100644 include/linux/pci-pwrseq.h