linux-kernel - Re: [PATCH v2 5/5] usb: dwc3-am62: add workaround for Errata i2409

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Message-ID: <330f901c-2d69-4666-90ed-9c558a4b3dfe@kernel.org>
Date: Thu, 8 Feb 2024 14:20:50 +0200
From: Roger Quadros <rogerq@...nel.org>
To: Andrew Davis <afd@...com>, Thinh.Nguyen@...opsys.com
Cc: gregkh@...uxfoundation.org, r-gunasekaran@...com, b-liu@...com,
 nm@...com, srk@...com, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH v2 5/5] usb: dwc3-am62: add workaround for Errata i2409



On 05/02/2024 20:07, Andrew Davis wrote:
> 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@...nel.org>
>> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
>> Cc: Conor Dooley <conor+dt@...nel.org>
>> Signed-off-by: Roger Quadros <rogerq@...nel.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.

Seems reasonable. Will fix.

> 
> 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);

-- 
cheers,
-roger