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

[Dmitry Baryshkov]

On Wed, 17 Jan 2024 at 18:08, Bartosz Golaszewski <brgl at bgdev.pl> wrote:
>
> From: Bartosz Golaszewski <bartosz.golaszewski at 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.

I'd still like to see how this can be extended to handle BT power up,
having a single entity driving both of the BT and WiFI.

The device tree changes behave in exactly the opposite way: they
define regulators for the WiFi device, while the WiFi is not being
powered by these regulators. Both WiFi and BT are powered by the PMU,
which in turn consumes all specified regulators.

>
> 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
>
> --
> 2.40.1
>
>


-- 
With best wishes
Dmitry