linux-kernel - [PATCH v2] usb: dwc3: qcom: Defer dwc3-qcom probe if dwc3 isn't probed properly

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Date:   Fri, 15 Jul 2022 18:51:52 +0530
From:   Krishna Kurapati <quic_kriskura@...cinc.com>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Krishna Kurapati <quic_kriskura@...cinc.com>
Subject: [PATCH v2] usb: dwc3: qcom: Defer dwc3-qcom probe if dwc3 isn't probed properly

On SC7180 devices, it is observed that dwc3 probing is deferred
because device_links_check_suppliers() finds that '88e3000.phy'
isn't ready yet.

As a part of its probe call, dwc3-qcom driver checks if dwc3 core
is wakeup capable or not. If the dwc3 core is wakeup capable, driver
configures dwc-qcom's power domain to be always ON. Also it configures
dp/dm interrupts accordingly to support wakeup from system suspend.

More info regarding the same can be found at:
commit d9be8d5c5b03 ("usb: dwc3: qcom: Keep power domain on to retain controller status")
commit 6895ea55c385 ("usb: dwc3: qcom: Configure wakeup interrupts during suspend")

In the event, dwc3 probe gets deferred and is processed after dwc3-qcom
probe, driver ends up reading the wakeup capability of dwc3 core as false
leading to instability in suspend/resume path.

To avoid this scenario, ensure dwc3_probe is successful by checking
if appropriate driver is assigned to it or not after the of_platform_populate
call. If it isn't then defer dwc3-qcom probe as well.

Fixes: 649f5c842ba3 ("usb: dwc3: core: Host wake up support from system suspend")
Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
---
v2: Set return value to EPROBE_DEFER to drop reference to dwc3 node

 drivers/usb/dwc3/dwc3-qcom.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index 7703655..6676b39 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -722,6 +722,9 @@ static int dwc3_qcom_of_register_core(struct platform_device *pdev)
 		dev_err(dev, "failed to get dwc3 platform device\n");
 	}

+	if (!qcom->dwc3->dev.driver)
+		ret = -EPROBE_DEFER;
+
 node_put:
 	of_node_put(dwc3_np);

-- 
2.7.4