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

[François Roux]

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>
---
Changes in v2:
- Sign off with my full name.
- Use the Assisted-by format from Documentation/process/coding-assistants.rst.
- Add a Closes: tag pointing to the regression report.
No code change.

v1: https://lore.kernel.org/all/20261003091451.4727-1-franzelfranzel@xxxxxxxxx/

 drivers/power/sequencing/pwrseq-qcom-wcn.c | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/drivers/power/sequencing/pwrseq-qcom-wcn.c b/drivers/power/sequencing/pwrseq-qcom-wcn.c
index 7f88a29b2..636dd7e63 100644
--- a/drivers/power/sequencing/pwrseq-qcom-wcn.c
+++ b/drivers/power/sequencing/pwrseq-qcom-wcn.c
@@ -526,15 +526,8 @@ static int pwrseq_qcom_wcn_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(ctx->bt_gpio),
 				     "Failed to get the Bluetooth enable GPIO\n");
 
-	/*
-	 * FIXME: This should actually be GPIOD_OUT_LOW, but doing so would
-	 * cause the WLAN power to be toggled, resulting in PCIe link down.
-	 * Since the PCIe controller driver is not handling link down currently,
-	 * the device becomes unusable. So we need to keep this workaround until
-	 * the link down handling is implemented in the controller driver.
-	 */
 	ctx->wlan_gpio = devm_gpiod_get_optional(dev, "wlan-enable",
-						 GPIOD_ASIS);
+						 GPIOD_OUT_LOW);
 	if (IS_ERR(ctx->wlan_gpio))
 		return dev_err_probe(dev, PTR_ERR(ctx->wlan_gpio),
 				     "Failed to get the WLAN enable GPIO\n");
@@ -545,13 +538,6 @@ static int pwrseq_qcom_wcn_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(ctx->xo_clk_gpio),
 				     "Failed to get the XO_CLK GPIO\n");
 
-	/*
-	 * Set direction to output but keep the current value in order to not
-	 * disable the WLAN module accidentally if it's already powered on.
-	 */
-	gpiod_direction_output(ctx->wlan_gpio,
-			       gpiod_get_value_cansleep(ctx->wlan_gpio));
-
 	ctx->clk = devm_clk_get_optional(dev, NULL);
 	if (IS_ERR(ctx->clk))
 		return dev_err_probe(dev, PTR_ERR(ctx->clk),

base-commit: 6474fa070f2b8013b4b87350b775b8c3be6e8aac
-- 
2.56.0