From d2901e4798cb106d5b265aa4e3ae05c06bf2bd1c Mon Sep 17 00:00:00 2001

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

Date: Thu, 6 Sep 2012 17:10:48 +0200

Subject: [PATCH 360/366] ehci: Don't process too much frames in 1 timer tick

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).

Note at first I had MAX_FR_PER_TICK set to 8, which works well with newer

Linux guest kernels, but not with older ones (such as the RHEL-6 kernel).

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

---

 hw/usb/hcd-ehci.c | 9 +++++++++

 1 file changed, 9 insertions(+)

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

index 30d2b56..5398544 100644

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

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

@@ -140,6 +140,7 @@

 #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 MAX_FR_PER_TICK  4        /* Max frames to process in one timer tick */

 /*  Internal periodic / asynchronous schedule state machine states

  */

@@ -2460,6 +2461,14 @@ static void ehci_frame_timer(void *opaque)

             DPRINTF("WARNING - EHCI skipped %d frames\n", skipped_frames);

         }

+        /*

+         * Processing too much frames at once causes the Linux EHCI isoc

+         * scheduling code to fail packet re-submissions with -EFBIG.

+         */

+        if (frames > MAX_FR_PER_TICK) {

+            frames = MAX_FR_PER_TICK;

+        }

+

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

             ehci_update_frindex(ehci, 1);

             ehci_advance_periodic_state(ehci);

-- 

1.7.12