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@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); }