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

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

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.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/power/sequencing/pwrseq-qcom-wcn.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/power/sequencing/pwrseq-qcom-wcn.c b/drivers/power/sequencing/pwrseq-qcom-wcn.c
index cc03b5aaa8f2..9d6a68ac719f 100644
--- a/drivers/power/sequencing/pwrseq-qcom-wcn.c
+++ b/drivers/power/sequencing/pwrseq-qcom-wcn.c
@@ -396,6 +396,14 @@ 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. The driver model can
+	 * correctly handle provider <-> consumer dependencies but there is a
+	 * known issue with Qcom PCIe controllers where, if the device is
+	 * powered off abrubtly (without controller driver noticing), the PCIe
+	 * link moves to link down state. Until the link-down handling is
+	 * addressed in the controller driver, we need to keep this workaround.
+	 */
 	ctx->wlan_gpio = devm_gpiod_get_optional(dev, "wlan-enable",
 						 GPIOD_ASIS);
 	if (IS_ERR(ctx->wlan_gpio))
-- 
2.45.2