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

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Date: Thu, 1 Feb 2024 12:52:44 -0600
From: Andrew Davis <afd@...com>
To: Roger Quadros <rogerq@...nel.org>, <Thinh.Nguyen@...opsys.com>
CC: <gregkh@...uxfoundation.org>, <r-gunasekaran@...com>, <b-liu@...com>,
        <srk@...com>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] usb: dwc3-am62: add workaround for Errata i2409

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@...nel.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);