[U-Boot] [PATCH 1/1] dwc2 USB controller hangs with lan78xx

[Alexander Graf]

On 06/18/2018 08:56 PM, Andrew Thomas wrote:
> This bug is the combination of dwc2 USB controller and lan78xx
> USB ethernet controller, which is the combination in use on
> the Raspberry Pi Model 3 B+.
>
> When the host attempts to receive a packet, but a packet has not
> arrived, the lan78xx controller responds by setting BIR
> (Bulk-In Empty Response) to NAK. Unfortunately, this hangs
> the USB controller and requires the USB controller to
> be reset.
>
> The fix proposed is to have the lan78xx controller respond
> by setting BIR to ZLP.
>
> Signed-off-by: Andrew Thomas <andrew.thomas at oracle.com>

So why does this work for Linux? I can see that Linux also sets the BIR 
flag, so why don't we see the hang there?


Alex

> ---
>   drivers/usb/eth/lan78xx.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/eth/lan78xx.c b/drivers/usb/eth/lan78xx.c
> index c5ff379..e8ee665 100644
> --- a/drivers/usb/eth/lan78xx.c
> +++ b/drivers/usb/eth/lan78xx.c
> @@ -296,7 +296,7 @@ static int lan78xx_basic_reset(struct usb_device *udev,
>   	ret = lan7x_read_reg(udev, LAN78XX_USB_CFG0, &val);
>   	if (ret)
>   		return ret;
> -	val |= LAN78XX_USB_CFG0_BIR;
> +	val &= ~LAN78XX_USB_CFG0_BIR;
>   	return lan7x_write_reg(udev, LAN78XX_USB_CFG0, val);
>   }
>