JZ4740 USB Device Controller is not OTG compatible and does not have
DEVCTL register in silicon.
During ethernet-over-usb transactions, on reset, musb driver tries to
read from DEVCTL and consequently sets device as host (A-Device)
instead of peripheral (B-Device), which makes it a composite device to
the USB gadget driver.
This induces a kernel panic during power down where the USB gadget
driver does a null pointer dereference when trying to access the
composite device configuration.
On reset, do not rely on DEVCTL value for setting gadget peripheral
mode. Use is_otg flag instead to set it to B-Device.
Signed-off-by: Apelete Seketeli <apelete@xxxxxxxxxxxx>
---
drivers/usb/musb/musb_gadget.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index c410a7f..d4aa779 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -2119,7 +2119,15 @@ __acquires(musb->lock)
/* Normal reset, as B-Device;
* or else after HNP, as A-Device
*/
- if (devctl & MUSB_DEVCTL_BDEVICE) {
+ if (!musb->g.is_otg) {
+ /* USB device controllers that are not OTG compatible
+ * may not have DEVCTL register in silicon.
+ * In that case, do not rely on devctl for setting
+ * peripheral mode.
+ */
+ musb->xceiv->state = OTG_STATE_B_PERIPHERAL;
+ musb->g.is_a_peripheral = 0;
+ } else if (devctl & MUSB_DEVCTL_BDEVICE) {
musb->xceiv->state = OTG_STATE_B_PERIPHERAL;
musb->g.is_a_peripheral = 0;
} else {
--
1.7.10.4
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