From d1034a88fdd8ad693a5cc2cb75af946e1562ff09 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede@redhat.com>
Date: Mon, 10 Sep 2012 12:38:21 +0200
Subject: [PATCH 358/369] 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>
---
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..6ce727c 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