Re: [PATCH v2] power: sequencing: qcom-wcn: power off WLAN at probe

[Manivannan Sadhasivam]

On Tue, Oct 06, 2026 at 11:03:17AM +0300, Bartosz Golaszewski wrote:
> On Sun, 4 Oct 2026 18:51:24 +0200, "François Roux"
> <franzelfranzel@xxxxxxxxx> said:
> > The WLAN enable GPIO is requested with GPIOD_ASIS and then kept at its
> > current level, so that a WLAN module left powered on by the firmware is
> > not switched off. The FIXME explains why: toggling it would take the
> > PCIe link down, and the controller driver could not recover from that.
> >
> > That reasoning held while the PCIe link was trained before the
> > sequencer probed. Since commit b921aa3f8dec ("PCI/pwrctrl: Switch to
> > pwrctrl create, power on/off, destroy APIs"), qcom_pcie_host_init()
> > powers the endpoint through pwrctrl before it starts link training, and
> > defers until the pwrctrl driver is bound. That driver cannot bind
> > before this sequencer has probed. Power-on therefore always comes
> > before link training, and keeping the firmware state is now harmful.
> >
> > On the Microsoft Surface Pro 11 (X1E80100), the WCN7850 sits on a
> > PCIe port without a PERST# GPIO. While pci-pwrctrl-pwrseq is not yet
> > bound, the host init is deferred about ten times, and each attempt
> > powers the PHY and controller back down. The later power-on only sets
> > a GPIO that is already high, so the chip is never reset and the link
> > never comes up:
> >
> >   qcom-pcie 1c08000.pcie: Device found, but not active
> >
> > The endpoint is not enumerated and ath12k never probes. Bluetooth on
> > the same chip fails too ("QCA Failed to send TLV segment (-110)").
> >
> > Request the GPIO as GPIOD_OUT_LOW. The chip is then off when the
> > sequencer probes, and pwrctrl powers it up cleanly right before link
> > training. Drop the FIXME and the code that preserved the firmware
> > state.
> >
> > Tested on a Surface Pro 11:
> >  - b921aa3f8dec plus a one-line version of this change: endpoint
> >    enumerated at 2.4 s, ath12k and Bluetooth working.
> >  - next-20260929 plus this patch: "PCIe Gen.3 x2 link up" at 3.4 s,
> >    ath12k and Bluetooth working, Wi-Fi connected.
> > Without the change, neither kernel enumerates the endpoint.
> >
> > The culprit was found by bisecting v6.17..v7.1, with the DTB and
> > .config held constant.
> >
> > Fixes: b921aa3f8dec ("PCI/pwrctrl: Switch to pwrctrl create, power on/off, destroy APIs")
> > Closes: https://lore.kernel.org/all/CAPjyS8dY0Q_o3XmFjuKZZsjhzhoSNL+ZGJtw5cQt8HiV3sUtxA@xxxxxxxxxxxxxx/
> > Cc: stable@xxxxxxxxxxxxxxx
> > Assisted-by: LLM
> > Signed-off-by: François Roux <franzelfranzel@xxxxxxxxx>
> > ---
> 
> Mani: this looks good to me, any objections to me queuing it for v7.3?
> 

No objections from me. As the commit message stated clearly, we no longer need
to rely on firmware configured state.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>

- Mani

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