From 5eaa0aa86cc280105d99c391c26aac5f2b549ed9 Mon Sep 17 00:00:00 2001 From: Mathias Nyman Date: Fri, 15 Jan 2021 18:19:06 +0200 Subject: xhci: make sure TRB is fully written before giving it to the controller commit 576667bad341516edc4e18eb85acb0a2b4c9c9d9 upstream. Once the command ring doorbell is rung the xHC controller will parse all command TRBs on the command ring that have the cycle bit set properly. If the driver just started writing the next command TRB to the ring when hardware finished the previous TRB, then HW might fetch an incomplete TRB as long as its cycle bit set correctly. A command TRB is 16 bytes (128 bits) long. Driver writes the command TRB in four 32 bit chunks, with the chunk containing the cycle bit last. This does however not guarantee that chunks actually get written in that order. This was detected in stress testing when canceling URBs with several connected USB devices. Two consecutive "Set TR Dequeue pointer" commands got queued right after each other, and the second one was only partially written when the controller parsed it, causing the dequeue pointer to be set to bogus values. This was seen as error messages: "Mismatch between completed Set TR Deq Ptr command & xHCI internal state" Solution is to add a write memory barrier before writing the cycle bit. Cc: Tested-by: Ross Zwisler Signed-off-by: Mathias Nyman Link: https://lore.kernel.org/r/20210115161907.2875631-2-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci-ring.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/usb/host') diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 536251c6149d..a39b7a49b7cf 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -2840,6 +2840,8 @@ static void queue_trb(struct xhci_hcd *xhci, struct xhci_ring *ring, trb->field[0] = cpu_to_le32(field1); trb->field[1] = cpu_to_le32(field2); trb->field[2] = cpu_to_le32(field3); + /* make sure TRB is fully written before giving it to the controller */ + wmb(); trb->field[3] = cpu_to_le32(field4); inc_enq(xhci, ring, more_trbs_coming); } -- cgit v1.2.3