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xhci: dbc: Allow users to modify DbC poll interval via sysfs

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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.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Uday M Bhat 2024-06-26 15:48:18 +03:00 committed by Greg Kroah-Hartman
parent 7b59c0362a
commit de3edd47a1
3 changed files with 49 additions and 1 deletions
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10
Documentation/ABI/testing/sysfs-bus-pci-drivers-xhci_hcd
View File

@ -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.

38
drivers/usb/host/xhci-dbgcap.c
View File

@ -1150,11 +1150,48 @@ static ssize_t dbc_bInterfaceProtocol_store(struct device *dev,
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_attrs[] = {
&dev_attr_dbc.attr,
@ -1162,6 +1199,7 @@ static struct attribute *dbc_dev_attrs[] = {
&dev_attr_dbc_idProduct.attr,
&dev_attr_dbc_bcdDevice.attr,
&dev_attr_dbc_bInterfaceProtocol.attr,
&dev_attr_dbc_poll_interval_ms.attr,
NULL
};
ATTRIBUTE_GROUPS(dbc_dev);

2
drivers/usb/host/xhci-dbgcap.h
View File

@ -95,7 +95,7 @@ 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:
*/