Re: [PATCH 4/5] xhci: Fix command ring pointer corruption while aborting a command

Mathias Nyman
2021-10-29T12:47:03Z

> Thanks Mathias for the detailed explanation. Agree that your patch is good
> enough for the current situation. May be a TODO comment here would help.
>

Changed the patch to write the _next_ command instead of the current to CRCR.

Pavan, youling 257, I'd appreciate if you could give this one more patch a try.
Your cases are hard to reprodudce with my setup.

And if it works can I add your "Tested-by:" tags to it?

Thanks,
-Mathias

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 311597bba80e..eaa49aef2935 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -366,7 +366,9 @@ static void xhci_handle_stopped_cmd_ring(struct xhci_hcd *xhci,
/* Must be called with xhci->lock held, releases and aquires lock back */
static int xhci_abort_cmd_ring(struct xhci_hcd *xhci, unsigned long flags)
{
- u32 temp_32;
+ struct xhci_segment *new_seg = xhci->cmd_ring->deq_seg;
+ union xhci_trb *new_deq = xhci->cmd_ring->dequeue;
+ u64 crcr;
int ret;

xhci_dbg(xhci, "Abort command ring\n");
@@ -375,13 +377,18 @@ static int xhci_abort_cmd_ring(struct xhci_hcd *xhci, unsigned long flags)

/*
* The control bits like command stop, abort are located in lower
- * dword of the command ring control register. Limit the write
- * to the lower dword to avoid corrupting the command ring pointer
- * in case if the command ring is stopped by the time upper dword
- * is written.
+ * dword of the command ring control register.
+ * Some controllers require all 64 bits to be written to abort the ring.
+ * Make sure the upper dword is valid, pointing to the next command,
+ * avoiding corrupting the command ring pointer in case the command ring
+ * is stopped by the time the upper dword is written.
*/
- temp_32 = readl(&xhci->op_regs->cmd_ring);
- writel(temp_32 | CMD_RING_ABORT, &xhci->op_regs->cmd_ring);
+ next_trb(xhci, NULL, &new_seg, &new_deq);
+ if (trb_is_link(new_deq))
+ next_trb(xhci, NULL, &new_seg, &new_deq);
+
+ crcr = xhci_trb_virt_to_dma(new_seg, new_deq);
+ xhci_write_64(xhci, crcr | CMD_RING_ABORT, &xhci->op_regs->cmd_ring);

/* Section 4.6.1.2 of xHCI 1.0 spec says software should also time the
* completion of the Command Abort operation. If CRR is not negated in 5