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

[andrew thomas]

On 06/26/2018 04:36 AM, Alexander Graf wrote:
> 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?

Although I proposed a fix to the lan78xx controller, I didn't mean to
identify it as the culprit :-)

I don't understand the interaction of the dwc2 and lan78xx controller.

Maybe BIR works for linux, because the dwc2 controller sets up the USB
host interface "differently"? It's just a guess...

Maybe we can coax the lan78xx driver writer into looking into this issue?
[CCing Yuiko Oshino.]

Andrew


>
>
> 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);
>>   }
>
>