[PATCH v4 1/4] phy: qcom: qmp-combo: 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.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>
Reviewed-by: Abel Vesa <abel.vesa at oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio at oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain at oss.qualcomm.com>
---
 drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
index cdcfad2e86b1d37650c4d7b0433319837ee9c9d4..affc8e040bb968a5b9d0b6f6fc2694c471368729 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
@@ -4934,10 +4934,16 @@ static int qmp_combo_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.
@@ -4946,14 +4952,13 @@ static int qmp_combo_probe(struct platform_device *pdev)
 
 	ret = qmp_combo_register_clocks(qmp, usb_np, dp_np);
 	if (ret)
-		goto err_node_put;
-
+		goto err_pm_put;
 
 	qmp->usb_phy = devm_phy_create(dev, usb_np, &qmp_combo_usb_phy_ops);
 	if (IS_ERR(qmp->usb_phy)) {
 		ret = PTR_ERR(qmp->usb_phy);
 		dev_err(dev, "failed to create USB PHY: %d\n", ret);
-		goto err_node_put;
+		goto err_pm_put;
 	}
 
 	phy_set_drvdata(qmp->usb_phy, qmp);
@@ -4962,11 +4967,13 @@ static int qmp_combo_probe(struct platform_device *pdev)
 	if (IS_ERR(qmp->dp_phy)) {
 		ret = PTR_ERR(qmp->dp_phy);
 		dev_err(dev, "failed to create DP PHY: %d\n", ret);
-		goto err_node_put;
+		goto err_pm_put;
 	}
 
 	phy_set_drvdata(qmp->dp_phy, qmp);
 
+	pm_runtime_put(dev);
+
 	if (usb_np == dev->of_node)
 		phy_provider = devm_of_phy_provider_register(dev, qmp_combo_phy_xlate);
 	else
@@ -4977,6 +4984,8 @@ static int qmp_combo_probe(struct platform_device *pdev)
 
 	return PTR_ERR_OR_ZERO(phy_provider);
 
+err_pm_put:
+	pm_runtime_put_noidle(dev);
 err_node_put:
 	of_node_put(usb_np);
 	of_node_put(dp_np);

-- 
2.34.1