[PATCH] usb: dwc3: qcom: Make sure core device is fully initialized before it is used

[Matthias Kaehlcke <mka@chromium.org>]

dwc3_qcom_of_register_core() uses of_platform_populate() to add
the dwc3 core device. The driver core will try to probe the device,
however this might fail (e.g. due to deferred probing) and
of_platform_populate() would still return 0 if the device was
successully added to the platform bus. Verify that the core device
is actually bound to its driver before using it, defer probing of the
dwc3_qcom device if the core device isn't ready (yet).

Fixes: a4333c3a6ba9 ("usb: dwc3: Add Qualcomm DWC3 glue driver").
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
depends on:
  https://lore.kernel.org/patchwork/patch/1251661/ ("driver core:Export
    the symbol device_is_bound")

 drivers/usb/dwc3/dwc3-qcom.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index 1dfd024cd06b..5a9036b050c6 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -537,6 +537,16 @@ static int dwc3_qcom_of_register_core(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	/*
+	 * A successful return from of_platform_populate() only guarantees that
+	 * the core device was added to the platform bus, however it might not
+	 * be bound to its driver (e.g. due to deferred probing). This driver
+	 * requires the core device to be fully initialized, so defer probing
+	 * if it isn't ready (yet).
+	 */
+	if (!device_is_bound(&qcom->dwc3->dev))
+		return -EPROBE_DEFER;
+
 	return 0;
 }
 
-- 
2.27.0.290.gba653c62da-goog