On 6.3.2020 18.06, Al Cooper wrote: > Unable to complete the enumeration of a USB TV Tuner device. > > Per XHCI spec (4.6.5), the EP state field of the input context shall > be cleared for a set address command. In the special case of an FS > device that has "MaxPacketSize0 = 8", the Linux XHCI driver does > not do this before evaluating the context. With an XHCI controller > that checks the EP state field for parameter context error this > causes a problem in cases such as the device getting reset again > after enumeration. > > When that field is cleared, the problem does not occur. > > This was found and fixed by Sasi Kumar. > > Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx> > --- > drivers/usb/host/xhci.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c > index dbac0fa9748d..5f034e143082 100644 > --- a/drivers/usb/host/xhci.c > +++ b/drivers/usb/host/xhci.c > @@ -1428,6 +1428,7 @@ static int xhci_check_maxpacket(struct xhci_hcd *xhci, unsigned int slot_id, > xhci->devs[slot_id]->out_ctx, ep_index); > > ep_ctx = xhci_get_ep_ctx(xhci, command->in_ctx, ep_index); > + ep_ctx->ep_info &= cpu_to_le32(~EP_STATE_MASK);/* must clear */ > ep_ctx->ep_info2 &= cpu_to_le32(~MAX_PACKET_MASK); > ep_ctx->ep_info2 |= cpu_to_le32(MAX_PACKET(max_packet_size)); > > Thanks, nice catch. If you agree I'd like to change the the subject of this patch to something like: "xhci: Fix enumeration issue when setting actual max packet size for FS devices" While looking at this it seems that the current EP_STATE_MASK is not correct either. It should be 0x7 instead of 0xf. -Mathias
