This is a note to let you know that I've just added the patch titled
xhci: Clear EHB bit only at end of interrupt handler
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xhci-clear-ehb-bit-only-at-end-of-interrupt-handler.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 15f3ef070933817fac2bcbdb9c85bff9e54e9f80 Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@xxxxxxxxx>
Date: Fri, 15 Sep 2023 17:31:07 +0300
Subject: xhci: Clear EHB bit only at end of interrupt handler
From: Lukas Wunner <lukas@xxxxxxxxx>
commit 15f3ef070933817fac2bcbdb9c85bff9e54e9f80 upstream.
The Event Handler Busy bit shall be cleared by software when the Event
Ring is empty. The xHC is thereby informed that it may raise another
interrupt once it has enqueued new events (sec 4.17.2).
However since commit dc0ffbea5729 ("usb: host: xhci: update event ring
dequeue pointer on purpose"), the EHB bit is already cleared after half
a segment has been processed.
As a result, spurious interrupts may occur:
- xhci_irq() processes half a segment, clears EHB, continues processing
remaining events.
- xHC enqueues new events. Because EHB has been cleared, xHC sets
Interrupt Pending bit. Interrupt moderation countdown begins.
- Meanwhile xhci_irq() continues processing events. Interrupt
moderation countdown reaches zero, so an MSI interrupt is signaled.
- xhci_irq() empties the Event Ring, clears EHB again and is done.
- Because an MSI interrupt has been signaled, xhci_irq() is run again.
It discovers there's nothing to do and returns IRQ_NONE.
Avoid by clearing the EHB bit only at the end of xhci_irq().
Fixes: dc0ffbea5729 ("usb: host: xhci: update event ring dequeue pointer on purpose")
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.5+
Cc: Peter Chen <peter.chen@xxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230915143108.1532163-4-mathias.nyman@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/xhci-ring.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 98389b568633..3e5dc0723a8f 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2996,7 +2996,8 @@ static int xhci_handle_event(struct xhci_hcd *xhci, struct xhci_interrupter *ir)
*/
static void xhci_update_erst_dequeue(struct xhci_hcd *xhci,
struct xhci_interrupter *ir,
- union xhci_trb *event_ring_deq)
+ union xhci_trb *event_ring_deq,
+ bool clear_ehb)
{
u64 temp_64;
dma_addr_t deq;
@@ -3017,12 +3018,13 @@ static void xhci_update_erst_dequeue(struct xhci_hcd *xhci,
return;
/* Update HC event ring dequeue pointer */
- temp_64 &= ERST_PTR_MASK;
+ temp_64 &= ERST_DESI_MASK;
temp_64 |= ((u64) deq & (u64) ~ERST_PTR_MASK);
}
/* Clear the event handler busy flag (RW1C) */
- temp_64 |= ERST_EHB;
+ if (clear_ehb)
+ temp_64 |= ERST_EHB;
xhci_write_64(xhci, temp_64, &ir->ir_set->erst_dequeue);
}
@@ -3103,7 +3105,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
while (xhci_handle_event(xhci, ir) > 0) {
if (event_loop++ < TRBS_PER_SEGMENT / 2)
continue;
- xhci_update_erst_dequeue(xhci, ir, event_ring_deq);
+ xhci_update_erst_dequeue(xhci, ir, event_ring_deq, false);
event_ring_deq = ir->event_ring->dequeue;
/* ring is half-full, force isoc trbs to interrupt more often */
@@ -3113,7 +3115,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
event_loop = 0;
}
- xhci_update_erst_dequeue(xhci, ir, event_ring_deq);
+ xhci_update_erst_dequeue(xhci, ir, event_ring_deq, true);
ret = IRQ_HANDLED;
out:
--
2.42.0
Patches currently in stable-queue which might be from lukas@xxxxxxxxx are
queue-6.5/xhci-preserve-rsvdp-bits-in-erstba-register-correctly.patch
queue-6.5/xhci-clear-ehb-bit-only-at-end-of-interrupt-handler.patch
queue-6.5/serial-reduce-spinlocked-portion-of-uart_rs485_config.patch
