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.tho...@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);
}
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