Commit a60f39a4 authored by Miguel GAIO's avatar Miguel GAIO Committed by Gerd Hoffmann
Browse files

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: default avatarMiguel GAIO <mgaio35@gmail.com>
Message-Id: <20180927151936.3647-1-mgaio35@gmail.com>
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 3e9191ac

hw/usb/hcd-ohci.c

+5 −1
Original line number Diff line number Diff line
@@ -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)