Commit 80826240 authored by Hans de Goede's avatar Hans de Goede Committed by Gerd Hoffmann
Browse files

ehci: Lower timer freq when the periodic schedule is idle 



Lower the timer freq if no iso schedule packets complete for 64 frames in
a row.

We can safely do this, without adding latency, because:
1) If there is isoc traffic this will never trigger
2) For async handled interrupt packets (only usb-host), the completion handler
   will immediately schedule the frame_timer from a bh
3) All devices using NAK to signal no data for interrupt endpoints now use
   wakeup, which will immediately schedule the frame_timer from a bh

The advantage of this is that when we only have interrupt packets in the
periodic schedule, async_stepdown can do its work and significantly lower
the frequency at which the frame_timer runs.

Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 386ab487

hw/usb/hcd-ehci.c

+33 −6
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ 
#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

#define PERIODIC_ACTIVE  64



/*  Internal periodic / asynchronous schedule state machine states

 */
@@ -738,6 +739,19 @@ static int ehci_register_companion(USBBus *bus, USBPort *ports[], 
    return 0;

}



static void ehci_wakeup_endpoint(USBBus *bus, USBEndpoint *ep)

{

    EHCIState *s = container_of(bus, EHCIState, bus);

    uint32_t portsc = s->portsc[ep->dev->port->index];



    if (portsc & PORTSC_POWNER) {

        return;

    }



    s->periodic_sched_active = PERIODIC_ACTIVE;

    qemu_bh_schedule(s->async_bh);

}



static USBDevice *ehci_find_device(EHCIState *ehci, uint8_t addr)

{

    USBDevice *dev;
@@ -1188,9 +1202,10 @@ static void ehci_async_complete_packet(USBPort *port, USBPacket *packet) 
    trace_usb_ehci_packet_action(p->queue, p, "wakeup");

    p->async = EHCI_ASYNC_FINISHED;



    if (p->queue->async) {

        qemu_bh_schedule(p->queue->ehci->async_bh);

    if (!p->queue->async) {

        s->periodic_sched_active = PERIODIC_ACTIVE;

    }

    qemu_bh_schedule(s->async_bh);

}



static void ehci_execute_complete(EHCIQueue *q)
@@ -1344,6 +1359,8 @@ static int ehci_process_itd(EHCIState *ehci, 
    uint32_t i, len, pid, dir, devaddr, endp;

    uint32_t pg, off, ptr1, ptr2, max, mult;



    ehci->periodic_sched_active = PERIODIC_ACTIVE;



    dir =(itd->bufptr[1] & ITD_BUFPTR_DIRECTION);

    devaddr = get_field(itd->bufptr[0], ITD_BUFPTR_DEVADDR);

    endp = get_field(itd->bufptr[0], ITD_BUFPTR_EP);
@@ -2033,6 +2050,9 @@ static void ehci_advance_state(EHCIState *ehci, int async) 
        case EST_WRITEBACK:

            assert(q != NULL);

            again = ehci_state_writeback(q);

            if (!async) {

                ehci->periodic_sched_active = PERIODIC_ACTIVE;

            }

            break;



        default:
@@ -2198,7 +2218,6 @@ static void ehci_frame_timer(void *opaque) 


    if (ehci_periodic_enabled(ehci) || ehci->pstate != EST_INACTIVE) {

        need_timer++;

        ehci->async_stepdown = 0;



        if (frames > ehci->maxframes) {

            skipped_frames = frames - ehci->maxframes;
@@ -2222,18 +2241,25 @@ static void ehci_frame_timer(void *opaque) 
                    break;

                }

            }

            if (ehci->periodic_sched_active) {

                ehci->periodic_sched_active--;

            }

            ehci_update_frindex(ehci, 1);

            ehci_advance_periodic_state(ehci);

            ehci->last_run_ns += FRAME_TIMER_NS;

        }

    } else {

        if (ehci->async_stepdown < ehci->maxframes / 2) {

            ehci->async_stepdown++;

        }

        ehci->periodic_sched_active = 0;

        ehci_update_frindex(ehci, frames);

        ehci->last_run_ns += FRAME_TIMER_NS * frames;

    }



    if (ehci->periodic_sched_active) {

        ehci->async_stepdown = 0;

    } else if (ehci->async_stepdown < ehci->maxframes / 2) {

        ehci->async_stepdown++;

    }



    /*  Async is not inside loop since it executes everything it can once

     *  called

     */
@@ -2301,6 +2327,7 @@ static USBPortOps ehci_port_ops = { 


static USBBusOps ehci_bus_ops = {

    .register_companion = ehci_register_companion,

    .wakeup_endpoint = ehci_wakeup_endpoint,

};



static int usb_ehci_post_load(void *opaque, int version_id)

hw/usb/hcd-ehci.h

+1 −0
Original line number Diff line number Diff line
@@ -311,6 +311,7 @@ struct EHCIState { 


    uint64_t last_run_ns;

    uint32_t async_stepdown;

    uint32_t periodic_sched_active;

    bool int_req_by_async;

};