[PATCH v4 2/4] phy: qcom: qmp-usbc: Prevent unnecessary PM runtime suspend at boot

[Loic Poulain]

Runtime PM has to be enabled before creating the PHYs, since phy_create()
only enables runtime PM on the PHY devices if it is already enabled on
this parent device. This opens a small window where the device can be
runtime suspended after pm_runtime_enable() and before the later
pm_runtime_forbid(), causing an unnecessary suspend/resume cycle while
the PHYs are not yet registered.

Take a runtime PM usage reference with pm_runtime_get_noresume() before
enabling runtime PM and release it once the PHYs have been created to
prevent the device from being runtime suspended during that window.

Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxxxxxxxx>
Reviewed-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
Reviewed-by: Abel Vesa <abel.vesa@xxxxxxxxxxxxxxxx>
---
 drivers/phy/qualcomm/phy-qcom-qmp-usbc.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c b/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c
index ab3055bb5b0c198832ae06dfcd04fd34395e271d..4317224070fd8dec98090e9200ac7d0e97265979 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c
@@ -1959,10 +1959,16 @@ static int qmp_usbc_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_node_put;
 
+	/*
+	 * Enable runtime PM before creating the PHYs, phy_create() only enables
+	 * it on the PHY devices if already enabled on the parent. Hold a usage
+	 * reference so callbacks cannot run until the PHY is ready.
+	 */
+	pm_runtime_get_noresume(dev);
 	pm_runtime_set_active(dev);
 	ret = devm_pm_runtime_enable(dev);
 	if (ret)
-		goto err_node_put;
+		goto err_pm_put;
 	/*
 	 * Prevent runtime pm from being ON by default. Users can enable
 	 * it using power/control in sysfs.
@@ -1971,13 +1977,13 @@ static int qmp_usbc_probe(struct platform_device *pdev)
 
 	ret = qmp_usbc_register_clocks(qmp, np);
 	if (ret)
-		goto err_node_put;
+		goto err_pm_put;
 
 	qmp->usb_phy = devm_phy_create(dev, np, &qmp_usbc_usb_phy_ops);
 	if (IS_ERR(qmp->usb_phy)) {
 		ret = PTR_ERR(qmp->usb_phy);
 		dev_err(dev, "failed to create PHY: %d\n", ret);
-		goto err_node_put;
+		goto err_pm_put;
 	}
 
 	phy_set_drvdata(qmp->usb_phy, qmp);
@@ -1987,17 +1993,21 @@ static int qmp_usbc_probe(struct platform_device *pdev)
 		if (IS_ERR(qmp->dp_phy)) {
 			ret = PTR_ERR(qmp->dp_phy);
 			dev_err(dev, "failed to create PHY: %d\n", ret);
-			goto err_node_put;
+			goto err_pm_put;
 		}
 		phy_set_drvdata(qmp->dp_phy, qmp);
 	}
 
+	pm_runtime_put(dev);
+
 	of_node_put(np);
 
 	phy_provider = devm_of_phy_provider_register(dev, qmp_usbc_phy_xlate);
 
 	return PTR_ERR_OR_ZERO(phy_provider);
 
+err_pm_put:
+	pm_runtime_put_noidle(dev);
 err_node_put:
 	of_node_put(np);
 	return ret;

-- 
2.34.1