usb: xhci: remove infinite loop prevention

If a buggy HW reports some unpredicted event (for example, an overrun event
following a MSE event while the EP ring is actually not empty), the driver
will never find the TD, and it will loop until the TD list is empty.

Before commits [1][2], the spin lock was released when giving back a URB in
the do-while loop. This could cause more TD to be added to TD list, causing
an infinite loop.

Because of commits [1][2] the spin lock is not released any more, thus the
infinite loop prevention is unnecessary and is removed.

[1], commit 0c03d89d0c71 ("xhci: Giveback urb in finish_td directly")
[2], commit 36dc01657b49 ("usb: host: xhci: Support running urb giveback in
			   tasklet context")

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240626124835.1023046-18-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 8289f69a6978e4ec167616dd9608c0f5903e6f9b..7baa9dc706a1387f63c989d6a802413c0c5659e5 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2611,7 +2611,6 @@ static int handle_tx_event(struct xhci_hcd *xhci,
        int status = -EINPROGRESS;
        struct xhci_ep_ctx *ep_ctx;
        u32 trb_comp_code;
-       int td_num = 0;
 
        slot_id = TRB_TO_SLOT_ID(le32_to_cpu(event->flags));
        ep_index = TRB_TO_EP_ID(le32_to_cpu(event->flags)) - 1;
@@ -2637,10 +2636,6 @@ static int handle_tx_event(struct xhci_hcd *xhci,
        if (!ep_ring)
                return handle_transferless_tx_event(xhci, ep, trb_comp_code);
 
-       /* Count current td numbers if ep->skip is set */
-       if (ep->skip)
-               td_num += list_count_nodes(&ep_ring->td_list);
-
        /* Look for common error cases */
        switch (trb_comp_code) {
        /* Skip codes that require special handling depending on
@@ -2799,18 +2794,8 @@ static int handle_tx_event(struct xhci_hcd *xhci,
                        return 0;
                }
 
-               /* We've skipped all the TDs on the ep ring when ep->skip set */
-               if (ep->skip && td_num == 0) {
-                       ep->skip = false;
-                       xhci_dbg(xhci, "All tds on the ep_ring skipped. Clear skip flag for slot %u ep %u.\n",
-                                slot_id, ep_index);
-                       return 0;
-               }
-
                td = list_first_entry(&ep_ring->td_list, struct xhci_td,
                                      td_list);
-               if (ep->skip)
-                       td_num--;
 
                /* Is this a TRB in the currently executing TD? */
                ep_seg = trb_in_td(xhci, td, ep_trb_dma, false);