According to specification 6.5.6 FrameNumberOverflow Event when bit 15
of frame count changes (either from 1 to 0 or 0 to 1) a
FrameNumberOverflow interrupt should be generated. This fixes
usb-audio on mac99,via=pmu with MacOS 9.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3274
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Tested-by: Elisey Konstantinov <elisey.konstantinov@gmail.com>
---
v2:
- updated commit message
- added Tested-by and Resolves tags

 hw/usb/hcd-ohci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
index c7e9c71903..f8da16bc8f 100644
--- a/hw/usb/hcd-ohci.c
+++ b/hw/usb/hcd-ohci.c
@@ -1246,6 +1246,9 @@ static void ohci_frame_boundary(void *opaque)
     hcca.frame = cpu_to_le16(ohci->frame_number);
     /* When the HC updates frame number, set pad to 0. Ref OHCI Spec 4.4.1*/
     hcca.pad = 0;
+    if (ohci->frame_number == 0x8000 || ohci->frame_number == 0) {
+        ohci_set_interrupt(ohci, OHCI_INTR_FNO);
+    }
 
     if (ohci->done_count == 0 && !(ohci->intr_status & OHCI_INTR_WD)) {
         if (!ohci->done) {
-- 
2.41.3

On Thu, 12 Feb 2026 at 18:54, BALATON Zoltan <balaton@eik.bme.hu> wrote:
>
> According to specification 6.5.6 FrameNumberOverflow Event when bit 15
> of frame count changes (either from 1 to 0 or 0 to 1) a
> FrameNumberOverflow interrupt should be generated. This fixes
> usb-audio on mac99,via=pmu with MacOS 9.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3274
> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> Tested-by: Elisey Konstantinov <elisey.konstantinov@gmail.com>
> ---
> v2:
> - updated commit message
> - added Tested-by and Resolves tags
>
>  hw/usb/hcd-ohci.c | 3 +++
>  1 file changed, 3 insertions(+)

Applied to target-arm.next, thanks.

-- PMM