[Qemu-devel] PATCH: QEMU support for UHCI suspend / remote wake up

[Marcelo Tosatti <mtosatti@redhat.com>]

This patch enables USB UHCI global suspend/resume feature. The OS will
stop the HC once all ports are suspended. If there is activity on the
port(s), an interrupt signalling remote wakeup will be triggered.

To enable autosuspend for the USB tablet on Linux guests:

echo auto > /sys/devices/pci0000:00/0000:00:01.2/usb1/1-1/power/level

It reduces CPU consumption of an idle FC12 guest from 2.7% to 0.3%.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/hw/usb-hid.c b/hw/usb-hid.c
index 882d933..b7a4dc1 100644
--- a/hw/usb-hid.c
+++ b/hw/usb-hid.c
@@ -412,6 +412,9 @@ static void usb_hid_changed(USBHIDState *hs)
 
     if (hs->datain)
         hs->datain(hs->datain_opaque);
+
+    if (hs->dev.remote_wakeup)
+        usb_remote_wakeup(&hs->dev);
 }
 
 static void usb_mouse_event(void *opaque,
diff --git a/hw/usb-uhci.c b/hw/usb-uhci.c
index 1d83400..674cb0c 100644
--- a/hw/usb-uhci.c
+++ b/hw/usb-uhci.c
@@ -59,6 +59,7 @@
 
 #define UHCI_PORT_RESET (1 << 9)
 #define UHCI_PORT_LSDA  (1 << 8)
+#define UHCI_PORT_RD    (1 << 6)
 #define UHCI_PORT_ENC   (1 << 3)
 #define UHCI_PORT_EN    (1 << 2)
 #define UHCI_PORT_CSC   (1 << 1)
@@ -501,6 +502,7 @@ static void uhci_ioport_writew(void *opaque, uint32_t addr, uint32_t val)
             port->ctrl = (port->ctrl & 0x01fb) | (val & ~0x01fb);
             /* some bits are reset when a '1' is written to them */
             port->ctrl &= ~(val & 0x000a);
+            port->ctrl &= ~(port->ctrl & 0x0040); /* clear port resume detected */
         }
         break;
     }
@@ -593,6 +595,43 @@ static void uhci_resume (void *opaque)
     }
 }
 
+static UHCIPort *find_port(UHCIState *s, USBDevice *d)
+{
+    int i;
+
+    for (i = 0; i < NB_PORTS; i++) {
+        UHCIPort *port = &s->ports[i];
+
+        if (d == port->port.dev) {
+            return port;
+        }
+    }
+
+    return NULL;
+}
+
+static void uhci_event(USBDevice *dev)
+{
+    USBBus *bus = usb_bus_from_device(dev);
+    UHCIState *s = container_of(bus, UHCIState, bus);
+
+    if (s->cmd & UHCI_CMD_EGSM) {
+        UHCIPort *port = find_port(s, dev);
+
+        if (!port) {
+            return;
+        }
+
+        if (port->ctrl & UHCI_PORT_RD) {
+            return;
+        }
+
+        port->ctrl |= UHCI_PORT_RD;
+
+        uhci_resume(s);
+    }
+}
+
 static void uhci_attach(USBPort *port1, USBDevice *dev)
 {
     UHCIState *s = port1->opaque;
@@ -602,6 +641,7 @@ static void uhci_attach(USBPort *port1, USBDevice *dev)
         if (port->port.dev) {
             usb_attach(port1, NULL);
         }
+        dev->info->remote_wakeup_cb = uhci_event;
         /* set connect status */
         port->ctrl |= UHCI_PORT_CCS | UHCI_PORT_CSC;
 
diff --git a/hw/usb.c b/hw/usb.c
index a326bcf..9b24d49 100644
--- a/hw/usb.c
+++ b/hw/usb.c
@@ -229,3 +229,9 @@ void usb_send_msg(USBDevice *dev, int msg)
 
     /* This _must_ be synchronous */
 }
+
+void usb_remote_wakeup(USBDevice *dev)
+{
+    if (dev->info->remote_wakeup_cb)
+        dev->info->remote_wakeup_cb(dev);
+}
diff --git a/hw/usb.h b/hw/usb.h
index 00d2802..16de1c9 100644
--- a/hw/usb.h
+++ b/hw/usb.h
@@ -189,6 +189,11 @@ struct USBDeviceInfo {
      */
     int (*handle_data)(USBDevice *dev, USBPacket *p);
 
+    /*
+     * Process remote wakeup request.
+     */
+    void (*remote_wakeup_cb)(USBDevice *dev);
+
     const char *product_desc;
 
     /* handle legacy -usbdevice command line options */
@@ -317,6 +322,7 @@ void usb_unregister_port(USBBus *bus, USBPort *port);
 int usb_device_attach(USBDevice *dev);
 int usb_device_detach(USBDevice *dev);
 int usb_device_delete_addr(int busnr, int addr);
+void usb_remote_wakeup(USBDevice *dev);
 
 static inline USBBus *usb_bus_from_device(USBDevice *d)
 {