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

Andrew Davis
2024-02-01T18:52:49Z

On 2/1/24 6:12 AM, Roger Quadros wrote:
> 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;

Why do you need this in the driver data? You only use it in probe(),
just have it be a local variable.

> 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)
> +{

Do you really need these one line functions? They add more code than
they save and just hide a single deference? Just do that directly.

Andrew

> + 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);