power: sequencing: qcom-wcn: explain why we need the WLAN_EN GPIO hack

With the recent rework of the PCI power control code, the workaround for
the wlan-enable GPIO - where we don't set a default (low) state in the
power sequencing driver, but instead request the pin as-is - should no
longer be needed but some platforms still fail to probe the WLAN
controller. This is caused by the Qcom PCIe controller and needs a
workaround in the controller driver so add a FIXME to eventually remove
the hack from this driver once this is done.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Bartosz Golaszewski <[email protected]>

Author: Bartosz Golaszewski

drivers/power/sequencing/pwrseq-qcom-wcn.c

@@ -396,6 +396,13 @@ 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);
 	if (IS_ERR(ctx->wlan_gpio))