[PATCH v2] usb: dwc3: dwc3-am62: Re-initialize controller if lost power in PM suspend

[Roger Quadros]

If controller looses power during PM suspend then re-initialize
it. We use the DEBUG_CFG register to track if controller lost power
or was reset in PM suspend.

Move all initialization code into dwc3_ti_init() so it can be re-used.

Signed-off-by: Roger Quadros <rogerq@xxxxxxxxxx>
---
Changes in v2:
- fixed macro USBSS_DEBUG_CFG_OFF to 0
- Link to v1: https://lore.kernel.org/r/20241122-am62-dwc3-io-ddr-v1-1-cc4956449420@xxxxxxxxxx
---
 drivers/usb/dwc3/dwc3-am62.c | 82 +++++++++++++++++++++++++++++---------------
 1 file changed, 55 insertions(+), 27 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-am62.c b/drivers/usb/dwc3/dwc3-am62.c
index 5e3d1741701f..7eef945b1f89 100644
--- a/drivers/usb/dwc3/dwc3-am62.c
+++ b/drivers/usb/dwc3/dwc3-am62.c
@@ -108,6 +108,9 @@
 
 #define DWC3_AM62_AUTOSUSPEND_DELAY	100
 
+#define USBSS_DEBUG_CFG_OFF		0x0
+#define USBSS_DEBUG_CFG_DISABLED	0x7
+
 struct dwc3_am62 {
 	struct device *dev;
 	void __iomem *usbss;
@@ -117,6 +120,7 @@ struct dwc3_am62 {
 	unsigned int offset;
 	unsigned int vbus_divider;
 	u32 wakeup_stat;
+	void __iomem *phy;
 };
 
 static const int dwc3_ti_rate_table[] = {	/* in KHZ */
@@ -184,15 +188,47 @@ static int phy_syscon_pll_refclk(struct dwc3_am62 *am62)
 	return 0;
 }
 
+static int dwc3_ti_init(struct dwc3_am62 *am62)
+{
+	int ret;
+	u32 reg;
+
+	/* Read the syscon property and set the rate code */
+	ret = phy_syscon_pll_refclk(am62);
+	if (ret)
+		return ret;
+
+	/* Workaround Errata i2409 */
+	if (am62->phy) {
+		reg = readl(am62->phy + USB_PHY_PLL_REG12);
+		reg |= USB_PHY_PLL_LDO_REF_EN | USB_PHY_PLL_LDO_REF_EN_EN;
+		writel(reg, am62->phy + USB_PHY_PLL_REG12);
+	}
+
+	/* VBUS divider select */
+	reg = dwc3_ti_readl(am62, USBSS_PHY_CONFIG);
+	if (am62->vbus_divider)
+		reg |= 1 << USBSS_PHY_VBUS_SEL_SHIFT;
+
+	dwc3_ti_writel(am62, USBSS_PHY_CONFIG, reg);
+
+	clk_prepare_enable(am62->usb2_refclk);
+
+	/* Set mode valid bit to indicate role is valid */
+	reg = dwc3_ti_readl(am62, USBSS_MODE_CONTROL);
+	reg |= USBSS_MODE_VALID;
+	dwc3_ti_writel(am62, USBSS_MODE_CONTROL, reg);
+
+	return 0;
+}
+
 static int dwc3_ti_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct device_node *node = pdev->dev.of_node;
 	struct dwc3_am62 *am62;
 	unsigned long rate;
-	void __iomem *phy;
 	int i, ret;
-	u32 reg;
 
 	am62 = devm_kzalloc(dev, sizeof(*am62), GFP_KERNEL);
 	if (!am62)
@@ -228,29 +264,17 @@ static int dwc3_ti_probe(struct platform_device *pdev)
 
 	am62->rate_code = i;
 
-	/* Read the syscon property and set the rate code */
-	ret = phy_syscon_pll_refclk(am62);
-	if (ret)
-		return ret;
-
-	/* Workaround Errata i2409 */
-	phy = devm_platform_ioremap_resource(pdev, 1);
-	if (IS_ERR(phy)) {
+	am62->phy = devm_platform_ioremap_resource(pdev, 1);
+	if (IS_ERR(am62->phy)) {
 		dev_err(dev, "can't map PHY IOMEM resource. Won't apply i2409 fix.\n");
-		phy = NULL;
-	} else {
-		reg = readl(phy + USB_PHY_PLL_REG12);
-		reg |= USB_PHY_PLL_LDO_REF_EN | USB_PHY_PLL_LDO_REF_EN_EN;
-		writel(reg, phy + USB_PHY_PLL_REG12);
+		am62->phy = NULL;
 	}
 
-	/* VBUS divider select */
 	am62->vbus_divider = device_property_read_bool(dev, "ti,vbus-divider");
-	reg = dwc3_ti_readl(am62, USBSS_PHY_CONFIG);
-	if (am62->vbus_divider)
-		reg |= 1 << USBSS_PHY_VBUS_SEL_SHIFT;
 
-	dwc3_ti_writel(am62, USBSS_PHY_CONFIG, reg);
+	ret = dwc3_ti_init(am62);
+	if (ret)
+		return ret;
 
 	pm_runtime_set_active(dev);
 	pm_runtime_enable(dev);
@@ -258,7 +282,6 @@ static int dwc3_ti_probe(struct platform_device *pdev)
 	 * Don't ignore its dependencies with its children
 	 */
 	pm_suspend_ignore_children(dev, false);
-	clk_prepare_enable(am62->usb2_refclk);
 	pm_runtime_get_noresume(dev);
 
 	ret = of_platform_populate(node, NULL, NULL, dev);
@@ -267,11 +290,6 @@ static int dwc3_ti_probe(struct platform_device *pdev)
 		goto err_pm_disable;
 	}
 
-	/* Set mode valid bit to indicate role is valid */
-	reg = dwc3_ti_readl(am62, USBSS_MODE_CONTROL);
-	reg |= USBSS_MODE_VALID;
-	dwc3_ti_writel(am62, USBSS_MODE_CONTROL, reg);
-
 	/* Device has capability to wakeup system from sleep */
 	device_set_wakeup_capable(dev, true);
 	ret = device_wakeup_enable(dev);
@@ -338,6 +356,9 @@ static int dwc3_ti_suspend_common(struct device *dev)
 		dwc3_ti_writel(am62, USBSS_WAKEUP_STAT, USBSS_WAKEUP_STAT_CLR);
 	}
 
+	/* just to track if module resets on suspend */
+	dwc3_ti_writel(am62, USBSS_DEBUG_CFG, USBSS_DEBUG_CFG_DISABLED);
+
 	clk_disable_unprepare(am62->usb2_refclk);
 
 	return 0;
@@ -348,7 +369,14 @@ static int dwc3_ti_resume_common(struct device *dev)
 	struct dwc3_am62 *am62 = dev_get_drvdata(dev);
 	u32 reg;
 
-	clk_prepare_enable(am62->usb2_refclk);
+	reg = dwc3_ti_readl(am62, USBSS_DEBUG_CFG);
+	if (reg != USBSS_DEBUG_CFG_DISABLED) {
+		/* lost power/context */
+		dwc3_ti_init(am62);
+	} else {
+		dwc3_ti_writel(am62, USBSS_DEBUG_CFG, USBSS_DEBUG_CFG_OFF);
+		clk_prepare_enable(am62->usb2_refclk);
+	}
 
 	if (device_may_wakeup(dev)) {
 		/* Clear wakeup config enable bits */

---
base-commit: cdd30ebb1b9f36159d66f088b61aee264e649d7a
change-id: 20241122-am62-dwc3-io-ddr-3bcb683a91a0

Best regards,
-- 
Roger Quadros <rogerq@xxxxxxxxxx>