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Message-ID: <05a3ef7e-b4d6-4f87-b34d-cec5f4ecfb9f@ti.com>
Date: Mon, 5 Feb 2024 12:07:15 -0600
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Subject: Re: [PATCH v2 5/5] usb: dwc3-am62: add workaround for Errata i2409
Content-Language: en-US
To: Roger Quadros <rogerq@kernel.org>, <Thinh.Nguyen@synopsys.com>
CC: <gregkh@linuxfoundation.org>, <r-gunasekaran@ti.com>, <b-liu@ti.com>,
        <nm@ti.com>, <srk@ti.com>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Rob Herring <robh+dt@kernel.org>,
        Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley
	<conor+dt@kernel.org>
References: <20240205141221.56076-1-rogerq@kernel.org>
 <20240205141221.56076-6-rogerq@kernel.org>
From: Andrew Davis <afd@ti.com>
In-Reply-To: <20240205141221.56076-6-rogerq@kernel.org>
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On 2/5/24 8:12 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
> 
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Signed-off-by: Roger Quadros <rogerq@kernel.org>
> ---
> 
> Notes:
>      Changelog:
>      
>      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 | 21 ++++++++++++++++++++-
>   1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-am62.c b/drivers/usb/dwc3/dwc3-am62.c
> index af1ce934e7fb..5ae5c3087b0f 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);
> @@ -201,6 +207,12 @@ static int dwc3_ti_probe(struct platform_device *pdev)
>   		return PTR_ERR(am62->usbss);
>   	}
>   
> +	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;
> +	}

Why not move this down to where you use it below, then just have
it be an if/else with the work around in the if (!IS_ERR(phy))
and the warning in the else.

Andrew

> +
>   	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 +239,13 @@ static int dwc3_ti_probe(struct platform_device *pdev)
>   	if (ret)
>   		return ret;
>   
> +	/* Workaround Errata i2409 */
> +	if (phy) {
> +		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);