on AMD platforms with SNPS 3.1 USB controller if stop endpoint command is
issued the controller does not respond, when the EP is not in running
state. HW completes the command execution and reports
"Context State Error" completion code. This is as per the spec. However
HW on receiving the second command additionally marks EP to Flow control
state in HW which is RTL bug. This bug causes the HW not to respond
to any further doorbells that are rung by the driver. This makes the EP
to not functional anymore and causes gross functional failures.
As a workaround, not to hit this problem, its better we check the EP state
and issue the stop EP command only when the EP is in running state.
Also, with the inclusion of this patch, there maybe a possible race
condition that may get triggered as mentioned in the xHCI spec 4.6.9
Signed-off-by: Shyam Sundar S K <shyam-sundar....@amd.com>
Signed-off-by: Nehal Shah <nehal-bakulchandra.s...@amd.com>
---
drivers/usb/host/xhci-hub.c | 30 +++++++++++++++++++++---------
1 file changed, 21 insertions(+), 9 deletions(-)
diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 0dde49c..d39b1e0 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -398,17 +398,29 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int
slot_id, int suspend)
spin_lock_irqsave(&xhci->lock, flags);
for (i = LAST_EP_INDEX; i > 0; i--) {
if (virt_dev->eps[i].ring && virt_dev->eps[i].ring->dequeue) {
- struct xhci_command *command;
- command = xhci_alloc_command(xhci, false, false,
- GFP_NOWAIT);
- if (!command) {
- spin_unlock_irqrestore(&xhci->lock, flags);
- xhci_free_command(xhci, cmd);
- return -ENOMEM;
+ /* Check endpoint is running before stopping it,
+ * AMD SNPS 3.1 xHC may misbehave otherwise
+ */
+
+ struct xhci_ep_ctx *ep_ctx;
+
+ ep_ctx = xhci_get_ep_ctx(xhci, virt_dev->out_ctx, i);
+
+ if (GET_EP_CTX_STATE(ep_ctx) == EP_STATE_RUNNING) {
+ struct xhci_command *command;
+
+ command = xhci_alloc_command(xhci, false, false,
+ GFP_NOWAIT);
+ if (!command) {
+ spin_unlock_irqrestore(&xhci->lock,
+ flags);
+ xhci_free_command(xhci, cmd);
+ return -ENOMEM;
+ }
+ xhci_queue_stop_endpoint(xhci, command,
+ slot_id, i, suspend);
}
- xhci_queue_stop_endpoint(xhci, command, slot_id, i,
- suspend);
}
}
xhci_queue_stop_endpoint(xhci, cmd, slot_id, 0, suspend);
--
2.7.4
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