[PATCH 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>
---
 drivers/usb/dwc3/dwc3-am62.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/usb/dwc3/dwc3-am62.c b/drivers/usb/dwc3/dwc3-am62.c
index af1ce934e7fb..35d7a2fb128e 100644
--- a/drivers/usb/dwc3/dwc3-am62.c
+++ b/drivers/usb/dwc3/dwc3-am62.c
@@ -101,11 +101,17 @@
 #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 {
 	struct device *dev;
 	void __iomem *usbss;
+	void __iomem *phy;
 	struct clk *usb2_refclk;
 	int rate_code;
 	struct regmap *syscon;
@@ -140,6 +146,16 @@ static inline void dwc3_ti_writel(struct dwc3_am62 *am62, u32 offset, u32 value)
 	writel(value, (am62->usbss) + offset);
 }
 
+static inline u32 dwc3_ti_phy_readl(struct dwc3_am62 *am62, u32 offset)
+{
+	return readl((am62->phy) + offset);
+}
+
+static inline void dwc3_ti_phy_writel(struct dwc3_am62 *am62, u32 offset, u32 value)
+{
+	writel(value, (am62->phy) + offset);
+}
+
 static int phy_syscon_pll_refclk(struct dwc3_am62 *am62)
 {
 	struct device *dev = am62->dev;
@@ -201,6 +217,12 @@ static int dwc3_ti_probe(struct platform_device *pdev)
 		return PTR_ERR(am62->usbss);
 	}
 
+	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");
+		am62->phy = NULL;
+	}
+
 	am62->usb2_refclk = devm_clk_get(dev, "ref");
 	if (IS_ERR(am62->usb2_refclk)) {
 		dev_err(dev, "can't get usb2_refclk\n");
@@ -227,6 +249,13 @@ static int dwc3_ti_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	/* Workaround Errata i2409 */
+	if (am62->phy) {
+		reg = dwc3_ti_phy_readl(am62, USB_PHY_PLL_REG12);
+		reg |= USB_PHY_PLL_LDO_REF_EN | USB_PHY_PLL_LDO_REF_EN_EN;
+		dwc3_ti_phy_writel(am62, USB_PHY_PLL_REG12, reg);
+	}
+
 	/* 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