[PATCH 1/1] usb: dwc3: qcom: Keep wakeup option default off

[Peter Chen <peter.chen@oss.qualcomm.com>]

The "wakeup-source" property, as described in
Documentation/devicetree/bindings/power/wakeup-source.txt, only says
that a device is capable of waking up the system. Whether wakeup is
actually enabled is a policy decision, and drivers use
device_may_wakeup() to decide whether to arm the hardware wakeup logic.

Currently dwc3-qcom calls device_init_wakeup(dev, true) when the
property is present, so USB wakeup is enabled by default. Users who do
not want USB activity (e.g. connect/disconnect) to wake up the system
have to disable it through power/wakeup, otherwise unexpected wakeups
may happen.

Having wakeup enabled by default also costs power. In host mode, system
suspend skips dwc3_core_exit() and keeps the PHYs and the wakeup
detection logic powered so that the wakeup interrupts can fire, even on
systems where USB is never used as a wakeup source and the controller
could be fully powered off.

Keep the wakeup option default off and only mark the device as wakeup
capable, so that the user decides which USB controller is used as a
system wakeup source. Users who need it can enable it with:

  echo enabled > /sys/devices/.../<dwc3 device>/power/wakeup

While at it, drop the local wakeup_source variable and use
device_property_read_bool() like the other property reads in probe.

Signed-off-by: Peter Chen <peter.chen@oss.qualcomm.com>
---
 drivers/usb/dwc3/dwc3-qcom.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index ac68b4218b56..fb535e9a4a64 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -616,7 +616,6 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
 	struct resource		*r;
 	int			ret;
 	bool			ignore_pipe_clk;
-	bool			wakeup_source;
 
 	qcom = devm_kzalloc(&pdev->dev, sizeof(*qcom), GFP_KERNEL);
 	if (!qcom)
@@ -715,8 +714,8 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
 	if (ret)
 		goto remove_core;
 
-	wakeup_source = of_property_read_bool(dev->of_node, "wakeup-source");
-	device_init_wakeup(&pdev->dev, wakeup_source);
+	if (device_property_read_bool(dev, "wakeup-source"))
+		device_set_wakeup_capable(dev, true);
 
 	qcom->is_suspended = false;
 
-- 
2.43.0