xhci: dbc: poll at different rate depending on data transfer activity

[ Upstream commit fb18e5bb96603cc79d97f03e4c05f3992cf28624 ]

DbC driver starts polling for events immediately when DbC is enabled.
The current polling interval is 1ms, which keeps the CPU busy, impacting
power management even when there are no active data transfers.

Solve this by polling at a slower rate, with a 64ms interval as default
until a transfer request is queued, or if there are still are pending
unhandled transfers at event completion.

Tested-by: Uday M Bhat <uday.m.bhat@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240229141438.619372-9-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: f3d12ec847b9 ("xhci: dbc: fix bogus 1024 byte prefix if ttyDBC read races with stall event")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-dbgcap.c b/drivers/usb/host/xhci-dbgcap.c
index bfd437269800cf24738d0944df14c165b43ba776..3ca4145aeefa5fac21c672c520e67ba7c5065bc7 100644 (file)
--- a/drivers/usb/host/xhci-dbgcap.c
+++ b/drivers/usb/host/xhci-dbgcap.c
@@ -665,7 +665,8 @@ static int xhci_dbc_start(struct xhci_dbc *dbc)
                return ret;
        }
 
-       return mod_delayed_work(system_wq, &dbc->event_work, 1);
+       return mod_delayed_work(system_wq, &dbc->event_work,
+                               msecs_to_jiffies(dbc->poll_interval));
 }
 
 static void xhci_dbc_stop(struct xhci_dbc *dbc)
@@ -964,8 +965,10 @@ static void xhci_dbc_handle_events(struct work_struct *work)
        enum evtreturn          evtr;
        struct xhci_dbc         *dbc;
        unsigned long           flags;
+       unsigned int            poll_interval;
 
        dbc = container_of(to_delayed_work(work), struct xhci_dbc, event_work);
+       poll_interval = dbc->poll_interval;
 
        spin_lock_irqsave(&dbc->lock, flags);
        evtr = xhci_dbc_do_handle_events(dbc);
@@ -981,13 +984,18 @@ static void xhci_dbc_handle_events(struct work_struct *work)
                        dbc->driver->disconnect(dbc);
                break;
        case EVT_DONE:
+               /* set fast poll rate if there are pending data transfers */
+               if (!list_empty(&dbc->eps[BULK_OUT].list_pending) ||
+                   !list_empty(&dbc->eps[BULK_IN].list_pending))
+                       poll_interval = 1;
                break;
        default:
                dev_info(dbc->dev, "stop handling dbc events\n");
                return;
        }
 
-       mod_delayed_work(system_wq, &dbc->event_work, 1);
+       mod_delayed_work(system_wq, &dbc->event_work,
+                        msecs_to_jiffies(poll_interval));
 }
 
 static ssize_t dbc_show(struct device *dev,
@@ -1242,6 +1250,7 @@ xhci_alloc_dbc(struct device *dev, void __iomem *base, const struct dbc_driver *
        dbc->idVendor = DBC_VENDOR_ID;
        dbc->bcdDevice = DBC_DEVICE_REV;
        dbc->bInterfaceProtocol = DBC_PROTOCOL;
+       dbc->poll_interval = DBC_POLL_INTERVAL_DEFAULT;
 
        if (readl(&dbc->regs->control) & DBC_CTRL_DBC_ENABLE)
                goto err;

diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h
index 2de0dc49a3e9f72e67d4ac6906bc4259c036ea08..d165bafecd98fce3d7df731858b3acfb9798126c 100644 (file)
--- a/drivers/usb/host/xhci-dbgcap.h
+++ b/drivers/usb/host/xhci-dbgcap.h
@@ -93,6 +93,7 @@ struct dbc_ep {
 
 #define DBC_QUEUE_SIZE                 16
 #define DBC_WRITE_BUF_SIZE             8192
+#define DBC_POLL_INTERVAL_DEFAULT      64      /* milliseconds */
 
 /*
  * Private structure for DbC hardware state:
@@ -139,6 +140,7 @@ struct xhci_dbc {
 
        enum dbc_state                  state;
        struct delayed_work             event_work;
+       unsigned int                    poll_interval;  /* ms */
        unsigned                        resume_required:1;
        struct dbc_ep                   eps[2];