Re: [PATCH 3/3] usb: dwc3-am62: Fix up wake-up configuration and spurious wake up

[Roger Quadros <rogerq@kernel.org>]

Hi,

On 16/03/2023 15:12, Roger Quadros wrote:
> Explicitly set and clear wakeup config so we don't leave anything
> to chance.
> 
> Clear wakeup status on suspend so we know what caused wake up.
> 
> The LINESTATE wake up should not be enabled in device mode
> if we are not connected to a USB host else it will cause spurious
> wake up.
> 
> Signed-off-by: Roger Quadros <rogerq@kernel.org>
> ---
>  drivers/usb/dwc3/dwc3-am62.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-am62.c b/drivers/usb/dwc3/dwc3-am62.c
> index 859b48279658..af0524e2f1e1 100644
> --- a/drivers/usb/dwc3/dwc3-am62.c
> +++ b/drivers/usb/dwc3/dwc3-am62.c
> @@ -60,6 +60,13 @@
>  #define USBSS_WAKEUP_CFG_SESSVALID_EN	BIT(1)
>  #define USBSS_WAKEUP_CFG_VBUSVALID_EN	BIT(0)
>  
> +#define USBSS_WAKEUP_CFG_ALL	(USBSS_WAKEUP_CFG_VBUSVALID_EN | \
> +				 USBSS_WAKEUP_CFG_SESSVALID_EN | \
> +				 USBSS_WAKEUP_CFG_LINESTATE_EN | \
> +				 USBSS_WAKEUP_CFG_OVERCURRENT_EN)
> +
> +#define USBSS_WAKEUP_CFG_NONE	0
> +
>  /* WAKEUP STAT register bits */
>  #define USBSS_WAKEUP_STAT_OVERCURRENT	BIT(4)
>  #define USBSS_WAKEUP_STAT_LINESTATE	BIT(3)
> @@ -103,6 +110,7 @@ struct dwc3_data {
>  	struct regmap *syscon;
>  	unsigned int offset;
>  	unsigned int vbus_divider;
> +	u32 wakeup_stat;
>  };
>  
>  static const int dwc3_ti_rate_table[] = {	/* in KHZ */
> @@ -294,6 +302,7 @@ static int dwc3_ti_suspend_common(struct device *dev)
>  {
>  	struct dwc3_data *data = dev_get_drvdata(dev);
>  	u32 reg, current_prtcap_dir;
> +	u32 vbus_stat;
>  
>  	if (device_may_wakeup(dev)) {
>  		reg = dwc3_ti_readl(data, USBSS_CORE_STAT);
> @@ -302,12 +311,20 @@ static int dwc3_ti_suspend_common(struct device *dev)
>  		/* Set wakeup config enable bits */
>  		reg = dwc3_ti_readl(data, USBSS_WAKEUP_CONFIG);
>  		if (current_prtcap_dir == DWC3_GCTL_PRTCAP_HOST) {
> -			reg |= USBSS_WAKEUP_CFG_LINESTATE_EN | USBSS_WAKEUP_CFG_OVERCURRENT_EN;
> +			reg = USBSS_WAKEUP_CFG_LINESTATE_EN | USBSS_WAKEUP_CFG_OVERCURRENT_EN;
>  		} else {
> -			reg |= USBSS_WAKEUP_CFG_OVERCURRENT_EN | USBSS_WAKEUP_CFG_LINESTATE_EN |
> -			       USBSS_WAKEUP_CFG_VBUSVALID_EN;
> +			reg = USBSS_WAKEUP_CFG_VBUSVALID_EN | USBSS_WAKEUP_CFG_SESSVALID_EN;
> +			/*
> +			 * Enable LINESTATE wake up only if connected to bus else
> +			 * it causes spurious wake-up.
> +			 */
> +			vbus_stat = dwc3_ti_readl(data, USBSS_VBUS_STAT);
> +			if (vbus_stat & (USBSS_VBUS_STAT_SESSVALID | USBSS_VBUS_STAT_VBUSVALID))
> +				reg |= USBSS_WAKEUP_CFG_LINESTATE_EN;

There is one corner case where a spurious wake-up still happens.
i.e. If we are not in USB_SUSPEND state while entering SoC sleep.

So looks like we need to check if we are in USB SUSPEND before enabling
LINESTATE wakeup enable.

>  		}
>  		dwc3_ti_writel(data, USBSS_WAKEUP_CONFIG, reg);
> +		/* clear wakeup status so we know what caused the wake up */
> +		dwc3_ti_writel(data, USBSS_WAKEUP_STAT, USBSS_WAKEUP_STAT_CLR);
>  	}
>  
>  	clk_disable_unprepare(data->usb2_refclk);
> @@ -324,16 +341,11 @@ static int dwc3_ti_resume_common(struct device *dev)
>  
>  	if (device_may_wakeup(dev)) {
>  		/* Clear wakeup config enable bits */
> -		reg = dwc3_ti_readl(data, USBSS_WAKEUP_CONFIG);
> -		reg &= ~(USBSS_WAKEUP_CFG_OVERCURRENT_EN | USBSS_WAKEUP_CFG_LINESTATE_EN |
> -			 USBSS_WAKEUP_CFG_VBUSVALID_EN);
> -		dwc3_ti_writel(data, USBSS_WAKEUP_CONFIG, reg);
> +		dwc3_ti_writel(data, USBSS_WAKEUP_CONFIG, USBSS_WAKEUP_CFG_NONE);
>  	}
>  
>  	reg = dwc3_ti_readl(data, USBSS_WAKEUP_STAT);
> -	/* Clear the wakeup status with wakeup clear bit */
> -	reg |= USBSS_WAKEUP_STAT_CLR;
> -	dwc3_ti_writel(data, USBSS_WAKEUP_STAT, reg);
> +	data->wakeup_stat = reg;
>  
>  	return 0;
>  }

cheers,
-roger