USB: additional power savings for cdc-acm devices that support remote wakeup

this patch saves power for cdc-acm devices that support remote wakeup
while the device is connected.

- request needs_remote_wakeup when needed
- delayed write while a device is autoresumed
- the device is marked busy when appropriate

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 126 insertions, 21 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index c3201affa0b6..ba86fec872b4 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -159,12 +159,34 @@ static void acm_write_done(struct acm *acm, struct acm_wb *wb)
         spin_lock_irqsave(&acm->write_lock, flags);
         acm->write_ready = 1;
         wb->use = 0;
+        acm->transmitting--;
         spin_unlock_irqrestore(&acm->write_lock, flags);
 }
 
 /*
  * Poke write.
+ *
+ * the caller is responsible for locking
  */
+
+static int acm_start_wb(struct acm *acm, struct acm_wb *wb)
+{
+        int rc;
+
+        acm->transmitting++;
+
+        wb->urb->transfer_buffer = wb->buf;
+        wb->urb->transfer_dma = wb->dmah;
+        wb->urb->transfer_buffer_length = wb->len;
+        wb->urb->dev = acm->dev;
+
+        if ((rc = usb_submit_urb(wb->urb, GFP_ATOMIC)) < 0) {
+                dbg("usb_submit_urb(write bulk) failed: %d", rc);
+                acm_write_done(acm, wb);
+        }
+        return rc;
+}
+
 static int acm_write_start(struct acm *acm, int wbn)
 {
         unsigned long flags;
@@ -182,26 +204,31 @@ static int acm_write_start(struct acm *acm, int wbn)
                 return 0;       /* A white lie */
         }
 
+        wb = &acm->wb[wbn];
+        if(acm_wb_is_avail(acm) <= 1)
+                acm->write_ready = 0;
+
+        dbg("%s susp_count: %d", __func__, acm->susp_count);
+        if (acm->susp_count) {
+                acm->old_ready = acm->write_ready;
+                acm->delayed_wb = wb;
+                acm->write_ready = 0;
+                schedule_work(&acm->waker);
+                spin_unlock_irqrestore(&acm->write_lock, flags);
+                return 0;       /* A white lie */
+        }
+        usb_mark_last_busy(acm->dev);
+
         if (!acm_wb_is_used(acm, wbn)) {
                 spin_unlock_irqrestore(&acm->write_lock, flags);
                 return 0;
         }
-        wb = &acm->wb[wbn];
 
-        if(acm_wb_is_avail(acm) <= 1)
-                acm->write_ready = 0;
+        rc = acm_start_wb(acm, wb);
         spin_unlock_irqrestore(&acm->write_lock, flags);
 
-        wb->urb->transfer_buffer = wb->buf;
-        wb->urb->transfer_dma = wb->dmah;
-        wb->urb->transfer_buffer_length = wb->len;
-        wb->urb->dev = acm->dev;
-
-        if ((rc = usb_submit_urb(wb->urb, GFP_ATOMIC)) < 0) {
-                dbg("usb_submit_urb(write bulk) failed: %d", rc);
-                acm_write_done(acm, wb);
-        }
         return rc;
+
 }
 /*
  * attributes exported through sysfs
@@ -304,6 +331,7 @@ static void acm_ctrl_irq(struct urb *urb)
                         break;
         }
 exit:
+        usb_mark_last_busy(acm->dev);
         retval = usb_submit_urb (urb, GFP_ATOMIC);
         if (retval)
                 err ("%s - usb_submit_urb failed with result %d",
@@ -320,8 +348,11 @@ static void acm_read_bulk(struct urb *urb)
 
         dbg("Entering acm_read_bulk with status %d", status);
 
-        if (!ACM_READY(acm))
+        if (!ACM_READY(acm)) {
+                dev_dbg(&acm->data->dev, "Aborting, acm not ready");
                 return;
+        }
+        usb_mark_last_busy(acm->dev);
 
         if (status)
                 dev_dbg(&acm->data->dev, "bulk rx status %d\n", status);
@@ -331,6 +362,7 @@ static void acm_read_bulk(struct urb *urb)
 
         if (likely(status == 0)) {
                 spin_lock(&acm->read_lock);
+                acm->processing++;
                 list_add_tail(&rcv->list, &acm->spare_read_urbs);
                 list_add_tail(&buf->list, &acm->filled_read_bufs);
                 spin_unlock(&acm->read_lock);
@@ -343,7 +375,8 @@ static void acm_read_bulk(struct urb *urb)
                 /* nevertheless the tasklet must be kicked unconditionally
                 so the queue cannot dry up */
         }
-        tasklet_schedule(&acm->urb_task);
+        if (likely(!acm->susp_count))
+                tasklet_schedule(&acm->urb_task);
 }
 
 static void acm_rx_tasklet(unsigned long _acm)
@@ -354,16 +387,23 @@ static void acm_rx_tasklet(unsigned long _acm)
         struct acm_ru *rcv;
         unsigned long flags;
         unsigned char throttled;
+
         dbg("Entering acm_rx_tasklet");
 
         if (!ACM_READY(acm))
+        {
+                dbg("acm_rx_tasklet: ACM not ready");
                 return;
+        }
 
         spin_lock_irqsave(&acm->throttle_lock, flags);
         throttled = acm->throttle;
         spin_unlock_irqrestore(&acm->throttle_lock, flags);
         if (throttled)
+        {
+                dbg("acm_rx_tasklet: throttled");
                 return;
+        }
 
 next_buffer:
         spin_lock_irqsave(&acm->read_lock, flags);
@@ -403,6 +443,7 @@ urbs:
         while (!list_empty(&acm->spare_read_bufs)) {
                 spin_lock_irqsave(&acm->read_lock, flags);
                 if (list_empty(&acm->spare_read_urbs)) {
+                        acm->processing = 0;
                         spin_unlock_irqrestore(&acm->read_lock, flags);
                         return;
                 }
@@ -425,18 +466,23 @@ urbs:
                 rcv->urb->transfer_dma = buf->dma;
                 rcv->urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 
-                dbg("acm_rx_tasklet: sending urb 0x%p, rcv 0x%p, buf 0x%p", rcv->urb, rcv, buf);
-
                 /* This shouldn't kill the driver as unsuccessful URBs are returned to the
                    free-urbs-pool and resubmited ASAP */
-                if (usb_submit_urb(rcv->urb, GFP_ATOMIC) < 0) {
+                spin_lock_irqsave(&acm->read_lock, flags);
+                if (acm->susp_count || usb_submit_urb(rcv->urb, GFP_ATOMIC) < 0) {
                         list_add(&buf->list, &acm->spare_read_bufs);
-                        spin_lock_irqsave(&acm->read_lock, flags);
                         list_add(&rcv->list, &acm->spare_read_urbs);
+                        acm->processing = 0;
                         spin_unlock_irqrestore(&acm->read_lock, flags);
                         return;
+                } else {
+                        spin_unlock_irqrestore(&acm->read_lock, flags);
+                        dbg("acm_rx_tasklet: sending urb 0x%p, rcv 0x%p, buf 0x%p", rcv->urb, rcv, buf);
                 }
         }
+        spin_lock_irqsave(&acm->read_lock, flags);
+        acm->processing = 0;
+        spin_unlock_irqrestore(&acm->read_lock, flags);
 }
 
 /* data interface wrote those outgoing bytes */
@@ -463,6 +509,27 @@ static void acm_softint(struct work_struct *work)
         tty_wakeup(acm->tty);
 }
 
+static void acm_waker(struct work_struct *waker)
+{
+        struct acm *acm = container_of(waker, struct acm, waker);
+        long flags;
+        int rv;
+
+        rv = usb_autopm_get_interface(acm->control);
+        if (rv < 0) {
+                err("Autopm failure in %s", __func__);
+                return;
+        }
+        if (acm->delayed_wb) {
+                acm_start_wb(acm, acm->delayed_wb);
+                acm->delayed_wb = NULL;
+        }
+        spin_lock_irqsave(&acm->write_lock, flags);
+        acm->write_ready = acm->old_ready;
+        spin_unlock_irqrestore(&acm->write_lock, flags);
+        usb_autopm_put_interface(acm->control);
+}
+
 /*
  * TTY handlers
  */
@@ -492,6 +559,8 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
 
         if (usb_autopm_get_interface(acm->control) < 0)
                 goto early_bail;
+        else
+                acm->control->needs_remote_wakeup = 1;
 
         mutex_lock(&acm->mutex);
         if (acm->used++) {
@@ -509,6 +578,7 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
         if (0 > acm_set_control(acm, acm->ctrlout = ACM_CTRL_DTR | ACM_CTRL_RTS) &&
             (acm->ctrl_caps & USB_CDC_CAP_LINE))
                 goto full_bailout;
+        usb_autopm_put_interface(acm->control);
 
         INIT_LIST_HEAD(&acm->spare_read_urbs);
         INIT_LIST_HEAD(&acm->spare_read_bufs);
@@ -570,12 +640,14 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
         mutex_lock(&open_mutex);
         if (!--acm->used) {
                 if (acm->dev) {
+                        usb_autopm_get_interface(acm->control);
                         acm_set_control(acm, acm->ctrlout = 0);
                         usb_kill_urb(acm->ctrlurb);
                         for (i = 0; i < ACM_NW; i++)
                                 usb_kill_urb(acm->wb[i].urb);
                         for (i = 0; i < nr; i++)
                                 usb_kill_urb(acm->ru[i].urb);
+                        acm->control->needs_remote_wakeup = 0;
                         usb_autopm_put_interface(acm->control);
                 } else
                         acm_tty_unregister(acm);
@@ -987,6 +1059,7 @@ skip_normal_probe:
         acm->urb_task.func = acm_rx_tasklet;
         acm->urb_task.data = (unsigned long) acm;
         INIT_WORK(&acm->work, acm_softint);
+        INIT_WORK(&acm->waker, acm_waker);
         spin_lock_init(&acm->throttle_lock);
         spin_lock_init(&acm->write_lock);
         spin_lock_init(&acm->read_lock);
@@ -1116,6 +1189,7 @@ alloc_fail:
 static void stop_data_traffic(struct acm *acm)
 {
         int i;
+        dbg("Entering stop_data_traffic");
 
         tasklet_disable(&acm->urb_task);
 
@@ -1128,6 +1202,7 @@ static void stop_data_traffic(struct acm *acm)
         tasklet_enable(&acm->urb_task);
 
         cancel_work_sync(&acm->work);
+        cancel_work_sync(&acm->waker);
 }
 
 static void acm_disconnect(struct usb_interface *intf)
@@ -1181,8 +1256,27 @@ static void acm_disconnect(struct usb_interface *intf)
 static int acm_suspend(struct usb_interface *intf, pm_message_t message)
 {
         struct acm *acm = usb_get_intfdata(intf);
+        int cnt;
+
+        if (acm->dev->auto_pm) {
+                int b;
+
+                spin_lock_irq(&acm->read_lock);
+                spin_lock(&acm->write_lock);
+                b = acm->processing + acm->transmitting;
+                spin_unlock(&acm->write_lock);
+                spin_unlock_irq(&acm->read_lock);
+                if (b)
+                        return -EBUSY;
+        }
+
+        spin_lock_irq(&acm->read_lock);
+        spin_lock(&acm->write_lock);
+        cnt = acm->susp_count++;
+        spin_unlock(&acm->write_lock);
+        spin_unlock_irq(&acm->read_lock);
 
-        if (acm->susp_count++)
+        if (cnt)
                 return 0;
         /*
         we treat opened interfaces differently,
@@ -1201,15 +1295,21 @@ static int acm_resume(struct usb_interface *intf)
 {
         struct acm *acm = usb_get_intfdata(intf);
         int rv = 0;
+        int cnt;
 
-        if (--acm->susp_count)
+        spin_lock_irq(&acm->read_lock);
+        acm->susp_count -= 1;
+        cnt = acm->susp_count;
+        spin_unlock_irq(&acm->read_lock);
+
+        if (cnt)
                 return 0;
 
         mutex_lock(&acm->mutex);
         if (acm->used) {
                 rv = usb_submit_urb(acm->ctrlurb, GFP_NOIO);
                 if (rv < 0)
-                goto err_out;
+                        goto err_out;
 
                 tasklet_schedule(&acm->urb_task);
         }
diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index 046e064b033a..85c3aaaab7c5 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -107,10 +107,14 @@ struct acm {
         struct list_head filled_read_bufs;
         int write_used;                                 /* number of non-empty write buffers */
         int write_ready;                                /* write urb is not running */
+        int old_ready;
+        int processing;
+        int transmitting;
         spinlock_t write_lock;
         struct mutex mutex;
         struct usb_cdc_line_coding line;                /* bits, stop, parity */
         struct work_struct work;                        /* work queue entry for line discipline waking up */
+        struct work_struct waker;
         struct tasklet_struct urb_task;                 /* rx processing */
         spinlock_t throttle_lock;                       /* synchronize throtteling and read callback */
         unsigned int ctrlin;                            /* input control lines (DCD, DSR, RI, break, overruns) */
@@ -123,6 +127,7 @@ struct acm {
         unsigned char clocal;                           /* termios CLOCAL */
         unsigned int ctrl_caps;                         /* control capabilities from the class specific header */
         unsigned int susp_count;                        /* number of suspended interfaces */
+        struct acm_wb *delayed_wb;                      /* write queued for a device about to be woken */
 };
 
 #define CDC_DATA_INTERFACE_TYPE 0x0a