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ohci: set effectively usb frame rate to 1kHz 

USB frame rate is slightly lower than 1kHz: ie. ~950Hz.
Thus usb-audio device is not able to perform a simple audio playback
without underruns on audio backend.
eg. "-device pci-ohci,id=ohci -device usb-audio,bus=ohci.0" vs PulseAudio
backend. more than 50 underruns are observed per second.

Update ohci_sof_time computation, using QEMU_CLOCK_VIRTUAL in
ohci_usb_start(), and increment by usb_frame_time in ohci_sof()
makes USB frame rate close to 1kHz.
This way, no audio underrun are observed during audio playback.

Signed-off-by: Miguel GAIO <mgaio35@gmail.com>
Message-Id: <20180927151936.3647-1-mgaio35@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Miguel GAIO 2018-09-27 17:19:36 +02:00 committed by Gerd Hoffmann
parent 3e9191acb7
commit a60f39a468
1 changed files with 5 additions and 1 deletions
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6
hw/usb/hcd-ohci.c
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@ -1253,12 +1253,12 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head, int completion)
/* set a timer for EOF */
static void ohci_eof_timer(OHCIState *ohci)
{
ohci->sof_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
timer_mod(ohci->eof_timer, ohci->sof_time + usb_frame_time);
}
/* Set a timer for EOF and generate a SOF event */
static void ohci_sof(OHCIState *ohci)
{
ohci->sof_time += usb_frame_time;
ohci_eof_timer(ohci);
ohci_set_interrupt(ohci, OHCI_INTR_SF);
}
@ -1362,6 +1362,7 @@ static int ohci_bus_start(OHCIState *ohci)
* can meet some race conditions
*/
ohci->sof_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
ohci_eof_timer(ohci);
return 1;
@ -1476,6 +1477,9 @@ static uint32_t ohci_get_frame_remaining(OHCIState *ohci)
* set already.
*/
tks = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - ohci->sof_time;
if (tks < 0) {
tks = 0;
}
/* avoid muldiv if possible */
if (tks >= usb_frame_time)