[PATCH v4 4/4] usb: dwc3-am62: add workaround for Errata i2409

[Roger Quadros <rogerq@kernel.org>]

All AM62 devices have Errata i2409 [1] due to which
USB2 PHY may lock up due to short suspend.

Workaround involves setting bit 5 and 4 PLL_REG12
in PHY2 register space after USB controller is brought
out of LPSC reset but before controller initialization.

Handle this workaround.

[1] - https://www.ti.com/lit/er/sprz487d/sprz487d.pdf

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
---
Changelog:
v4: Added Acked-by
v3: move requesting of PHY2 region to right where we need it
v2: don't add phy read/write helpers or add phy to private data
v1: https://lore.kernel.org/all/20240201121220.5523-5-rogerq@kernel.org/
---
 drivers/usb/dwc3/dwc3-am62.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/dwc3-am62.c b/drivers/usb/dwc3/dwc3-am62.c
index 09b1f5a1c4fb..fad151e78fd6 100644
--- a/drivers/usb/dwc3/dwc3-am62.c
+++ b/drivers/usb/dwc3/dwc3-am62.c
@@ -101,6 +101,11 @@
 #define PHY_CORE_VOLTAGE_MASK	BIT(31)
 #define PHY_PLL_REFCLK_MASK	GENMASK(3, 0)
 
+/* USB PHY2 register offsets */
+#define	USB_PHY_PLL_REG12		0x130
+#define	USB_PHY_PLL_LDO_REF_EN		BIT(5)
+#define	USB_PHY_PLL_LDO_REF_EN_EN	BIT(4)
+
 #define DWC3_AM62_AUTOSUSPEND_DELAY	100
 
 struct dwc3_am62 {
@@ -184,8 +189,9 @@ 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;
-	int i, ret;
 	unsigned long rate;
+	void __iomem *phy;
+	int i, ret;
 	u32 reg;
 
 	am62 = devm_kzalloc(dev, sizeof(*am62), GFP_KERNEL);
@@ -227,6 +233,17 @@ static int dwc3_ti_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	/* Workaround Errata i2409 */
+	phy = devm_platform_ioremap_resource(pdev, 1);
+	if (IS_ERR(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);
+	}
+
 	/* VBUS divider select */
 	am62->vbus_divider = device_property_read_bool(dev, "ti,vbus-divider");
 	reg = dwc3_ti_readl(am62, USBSS_PHY_CONFIG);

-- 
2.34.1