[PATCH v6 3/6] phy: fsl-imx8mq-usb: add runtime PM support

[Xu Yang <xu.yang_2@oss.nxp.com>]

From: Xu Yang <xu.yang_2@nxp.com>

Add runtime PM to ensure the PHY is properly powered and clocked during
register access, preventing potential system hangs.

It guards register access in the following scenarios:
- PHY operations: init() and power_on/off() callbacks are guarded by
  phy core
- Type-C orientation switching when PHY/Controller are suspended which
  needs explicitly care
- Future PHY control port register regmap debugfs access

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

---
Changes in v6:
 - use devm_pm_runtime_enable() to disable runtime PM when probe fails
 - simply pm_runtime_get_sync/disable/put_noidle() to pm_runtime_resume()
Changes in v5:
 - use non-devm PM runtime callback to correctly enable/disable clocks
   when unbind the device
Changes in v4:
 - replace guard() with PM_RUNTIME_ACQUIRE()
Changes in v3:
 - new patch
---
 drivers/phy/freescale/phy-fsl-imx8mq-usb.c | 67 +++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 19 deletions(-)

diff --git a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
index 3a5788c609e1..bc804d2b5aee 100644
--- a/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
+++ b/drivers/phy/freescale/phy-fsl-imx8mq-usb.c
@@ -9,6 +9,7 @@
 #include <linux/of.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/regulator/consumer.h>
 #include <linux/usb/typec_mux.h>
 
@@ -136,17 +137,15 @@ static int tca_blk_typec_switch_set(struct typec_switch_dev *sw,
 {
 	struct imx8mq_usb_phy *imx_phy = typec_switch_get_drvdata(sw);
 	struct tca_blk *tca = imx_phy->tca;
-	int ret;
 
 	if (tca->orientation == orientation)
 		return 0;
 
-	ret = clk_prepare_enable(imx_phy->clk);
-	if (ret)
-		return ret;
+	PM_RUNTIME_ACQUIRE(&imx_phy->phy->dev, pm);
+	if (PM_RUNTIME_ACQUIRE_ERR(&pm))
+		return -ENXIO;
 
 	tca_blk_orientation_set(tca, orientation);
-	clk_disable_unprepare(imx_phy->clk);
 
 	return 0;
 }
@@ -620,16 +619,6 @@ static int imx8mq_phy_power_on(struct phy *phy)
 	if (ret)
 		return ret;
 
-	ret = clk_prepare_enable(imx_phy->clk);
-	if (ret)
-		return ret;
-
-	ret = clk_prepare_enable(imx_phy->alt_clk);
-	if (ret) {
-		clk_disable_unprepare(imx_phy->clk);
-		return ret;
-	}
-
 	/* Disable rx term override */
 	value = readl(imx_phy->base + PHY_CTRL6);
 	value &= ~PHY_CTRL6_RXTERM_OVERRIDE_SEL;
@@ -648,8 +637,6 @@ static int imx8mq_phy_power_off(struct phy *phy)
 	value |= PHY_CTRL6_RXTERM_OVERRIDE_SEL;
 	writel(value, imx_phy->base + PHY_CTRL6);
 
-	clk_disable_unprepare(imx_phy->alt_clk);
-	clk_disable_unprepare(imx_phy->clk);
 	regulator_disable(imx_phy->vbus);
 
 	return 0;
@@ -686,6 +673,7 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct imx8mq_usb_phy *imx_phy;
 	const struct phy_ops *phy_ops;
+	int ret;
 
 	imx_phy = devm_kzalloc(dev, sizeof(*imx_phy), GFP_KERNEL);
 	if (!imx_phy)
@@ -693,13 +681,13 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, imx_phy);
 
-	imx_phy->clk = devm_clk_get(dev, "phy");
+	imx_phy->clk = devm_clk_get_enabled(dev, "phy");
 	if (IS_ERR(imx_phy->clk)) {
 		dev_err(dev, "failed to get imx8mq usb phy clock\n");
 		return PTR_ERR(imx_phy->clk);
 	}
 
-	imx_phy->alt_clk = devm_clk_get_optional(dev, "alt");
+	imx_phy->alt_clk = devm_clk_get_optional_enabled(dev, "alt");
 	if (IS_ERR(imx_phy->alt_clk))
 		return dev_err_probe(dev, PTR_ERR(imx_phy->alt_clk),
 				    "Failed to get alt clk\n");
@@ -708,6 +696,11 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
 	if (IS_ERR(imx_phy->base))
 		return PTR_ERR(imx_phy->base);
 
+	pm_runtime_set_active(dev);
+	ret = devm_pm_runtime_enable(dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to enable runtime PM\n");
+
 	phy_ops = of_device_get_match_data(dev);
 	if (!phy_ops)
 		return -EINVAL;
@@ -737,15 +730,51 @@ static int imx8mq_usb_phy_probe(struct platform_device *pdev)
 
 static void imx8mq_usb_phy_remove(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
+
+	/* To allow devm-managed resources to be released cleanly */
+	if (pm_runtime_suspended(dev))
+		pm_runtime_resume(dev);
+}
+
+static int imx8mq_usb_phy_runtime_suspend(struct device *dev)
+{
+	struct imx8mq_usb_phy *imx_phy = dev_get_drvdata(dev);
+
+	clk_disable_unprepare(imx_phy->alt_clk);
+	clk_disable_unprepare(imx_phy->clk);
 
+	return 0;
 }
 
+static int imx8mq_usb_phy_runtime_resume(struct device *dev)
+{
+	struct imx8mq_usb_phy *imx_phy = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_prepare_enable(imx_phy->clk);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(imx_phy->alt_clk);
+	if (ret) {
+		clk_disable_unprepare(imx_phy->clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static DEFINE_RUNTIME_DEV_PM_OPS(imx8mq_usb_phy_pm_ops, imx8mq_usb_phy_runtime_suspend,
+				 imx8mq_usb_phy_runtime_resume, NULL);
+
 static struct platform_driver imx8mq_usb_phy_driver = {
 	.probe	= imx8mq_usb_phy_probe,
 	.remove = imx8mq_usb_phy_remove,
 	.driver = {
 		.name	= "imx8mq-usb-phy",
 		.of_match_table	= imx8mq_usb_phy_of_match,
+		.pm = pm_ptr(&imx8mq_usb_phy_pm_ops),
 		.suppress_bind_attrs = true,
 	}
 };

-- 
2.34.1