From a5022829821b27e00790f8fe2fd9cd8090a47e36 Mon Sep 17 00:00:00 2001

From: Hans de Goede <hdegoede@redhat.com>

Date: Mon, 10 Sep 2012 12:44:11 +0200

Subject: [PATCH] ehci: Don't process too much frames in 1 timer tick (v2)

The Linux ehci isoc scheduling code fills the entire schedule ahead of

time minus 80 frames. If we make a large jump in where we are in the

schedule, ie 40 frames, then the scheduler all of a sudden will only have

40 frames left to work in, causing it to fail packet submissions

with error -27 (-EFBIG).

Changes in v2:

-Don't hardcode a maximum number of frames to process in one tick, instead:

 -Process a minimum number of frames to ensure we do eventually catch up

 -Stop (after the minimum number) when the guest has requested an irq

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

(cherry picked from commit 8f74ed1e43263293301031a10e440549bab19a6e)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

---

 hw/usb/hcd-ehci.c | 14 ++++++++++++++

 1 file changed, 14 insertions(+)

diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c

index 54273d7..017a01d 100644

--- a/hw/usb/hcd-ehci.c

+++ b/hw/usb/hcd-ehci.c

@@ -139,6 +139,7 @@

 #define NB_PORTS         6        // Number of downstream ports

 #define BUFF_SIZE        5*4096   // Max bytes to transfer per transaction

 #define MAX_QH           100      // Max allowable queue heads in a chain

+#define MIN_FR_PER_TICK  3        // Min frames to process when catching up

 /*  Internal periodic / asynchronous schedule state machine states

  */

@@ -2448,6 +2449,19 @@ static void ehci_frame_timer(void *opaque)

         }

         for (i = 0; i < frames; i++) {

+            /*

+             * If we're running behind schedule, we should not catch up

+             * too fast, as that will make some guests unhappy:

+             * 1) We must process a minimum of MIN_FR_PER_TICK frames,

+             *    otherwise we will never catch up

+             * 2) Process frames until the guest has requested an irq (IOC)

+             */

+            if (i >= MIN_FR_PER_TICK) {

+                ehci_commit_irq(ehci);

+                if ((ehci->usbsts & USBINTR_MASK) & ehci->usbintr) {

+                    break;

+                }

+            }

             ehci_update_frindex(ehci, 1);

             ehci_advance_periodic_state(ehci);

             ehci->last_run_ns += FRAME_TIMER_NS;

-- 

1.7.12.1