6.6-stable review patch. If anyone has any objections, please let me know.
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From: Uday M Bhat uday.m.bhat@intel.com
[ Upstream commit de3edd47a18fe05a560847cc3165871474e08196 ]
xhci DbC driver polls the host controller for DbC events at a reduced rate when DbC is enabled but there are no active data transfers.
Allow users to modify this reduced poll interval via dbc_poll_interval_ms sysfs entry. Unit is milliseconds and accepted range is 0 to 5000. Max interval of 5000 ms is selected as it matches the common 5 second timeout used in usb stack. Default value is 64 milliseconds.
A long interval is useful when users know there won't be any activity on systems connected via DbC for long periods, and want to avoid battery drainage due to unnecessary CPU usage.
Example being Android Debugger (ADB) usage over DbC on ChromeOS systems running Android Runtime.
[minor changes and rewording -Mathias]
Co-developed-by: Samuel Jacob samjaco@google.com Signed-off-by: Samuel Jacob samjaco@google.com Signed-off-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/20240626124835.1023046-5-mathias.nyman@linux.intel... 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 --- Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd | 10 +++ drivers/usb/host/xhci-dbgcap.c | 38 +++++++++++++++ drivers/usb/host/xhci-dbgcap.h | 2 3 files changed, 49 insertions(+), 1 deletion(-)
--- a/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd +++ b/Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd @@ -75,3 +75,13 @@ Description: The default value is 1 (GNU Remote Debug command). Other permissible value is 0 which is for vendor defined debug target. + +What: /sys/bus/pci/drivers/xhci_hcd/.../dbc_poll_interval_ms +Date: February 2024 +Contact: Mathias Nyman mathias.nyman@linux.intel.com +Description: + This attribute adjust the polling interval used to check for + DbC events. Unit is milliseconds. Accepted values range from 0 + up to 5000. The default value is 64 ms. + This polling interval is used while DbC is enabled but has no + active data transfers. --- a/drivers/usb/host/xhci-dbgcap.c +++ b/drivers/usb/host/xhci-dbgcap.c @@ -1214,11 +1214,48 @@ static ssize_t dbc_bInterfaceProtocol_st return size; }
+static ssize_t dbc_poll_interval_ms_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct xhci_dbc *dbc; + struct xhci_hcd *xhci; + + xhci = hcd_to_xhci(dev_get_drvdata(dev)); + dbc = xhci->dbc; + + return sysfs_emit(buf, "%u\n", dbc->poll_interval); +} + +static ssize_t dbc_poll_interval_ms_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t size) +{ + struct xhci_dbc *dbc; + struct xhci_hcd *xhci; + u32 value; + int ret; + + ret = kstrtou32(buf, 0, &value); + if (ret || value > DBC_POLL_INTERVAL_MAX) + return -EINVAL; + + xhci = hcd_to_xhci(dev_get_drvdata(dev)); + dbc = xhci->dbc; + + dbc->poll_interval = value; + + mod_delayed_work(system_wq, &dbc->event_work, 0); + + return size; +} + static DEVICE_ATTR_RW(dbc); static DEVICE_ATTR_RW(dbc_idVendor); static DEVICE_ATTR_RW(dbc_idProduct); static DEVICE_ATTR_RW(dbc_bcdDevice); static DEVICE_ATTR_RW(dbc_bInterfaceProtocol); +static DEVICE_ATTR_RW(dbc_poll_interval_ms);
static struct attribute *dbc_dev_attributes[] = { &dev_attr_dbc.attr, @@ -1226,6 +1263,7 @@ static struct attribute *dbc_dev_attribu &dev_attr_dbc_idProduct.attr, &dev_attr_dbc_bcdDevice.attr, &dev_attr_dbc_bInterfaceProtocol.attr, + &dev_attr_dbc_poll_interval_ms.attr, NULL };
--- a/drivers/usb/host/xhci-dbgcap.h +++ b/drivers/usb/host/xhci-dbgcap.h @@ -94,7 +94,7 @@ struct dbc_ep { #define DBC_QUEUE_SIZE 16 #define DBC_WRITE_BUF_SIZE 8192 #define DBC_POLL_INTERVAL_DEFAULT 64 /* milliseconds */ - +#define DBC_POLL_INTERVAL_MAX 5000 /* milliseconds */ /* * Private structure for DbC hardware state: */