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

[Roger Quadros <rogerq@kernel.org>]

On 01/02/2024 20:52, Andrew Davis wrote:
> 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.

OK.

> 
>>       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.

Sure. Thanks.
> 
> 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);

-- 
cheers,
-roger