The "old" enumeration scheme is considerably faster (it takes
~244ms instead of ~356ms to get the descriptor).
It is currently only possible to use the old scheme globally
(/sys/module/usbcore/parameters/old_scheme_first), which is not
desirable as the new scheme was introduced to increase compatibility
with more devices.
However, in our case, we care about time-to-active for a specific
USB device (which we make the firmware for), on a specific port
(that is pogo-pin based: not a standard USB port). This new
sysfs option makes it possible to use the old scheme on a single
port only.
Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
---
Changes since v1:
- Added documentation in Documentation/ABI
- Updated timing in commit message to account for recent improvement
in USB core (74072bae88fb3b)
Documentation/ABI/testing/sysfs-bus-usb | 18 ++++++++++++++++++
drivers/usb/core/hub.c | 13 +++++++++----
drivers/usb/core/hub.h | 1 +
drivers/usb/core/port.c | 23 +++++++++++++++++++++++
include/linux/usb.h | 7 +++++++
5 files changed, 58 insertions(+), 4 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index c6e9b30f05b13..a31a66d62cbba 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -189,6 +189,24 @@ Description:
The file will read "hotplug", "wired" and "not used" if the
information is available, and "unknown" otherwise.
+What: /sys/bus/usb/devices/.../(hub interface)/portX/quirks
+Date: May 2018
+Contact: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
+Description:
+ In some cases, we care about time-to-active for devices
+ connected on a specific port (e.g. non-standard USB port like
+ pogo pins), where the device to be connected is known in
+ advance, and behaves well according to the specification.
+ This attribute is a bit-field that controls the behavior of
+ a specific port:
+ - Bit 0 of this field selects the "old" enumeration scheme,
+ as it is considerably faster (it only causes one USB reset
+ instead of 2).
+ The old enumeration scheme can also be selected globally
+ using /sys/module/usbcore/parameters/old_scheme_first, but
+ it is often not desirable as the new scheme was introduced to
+ increase compatibility with more devices.
+
What: /sys/bus/usb/devices/.../(hub interface)/portX/over_current_count
Date: February 2018
Contact: Richard Leitner <richard.leitner@xxxxxxxxxxx>
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index c2d993d3816f0..f900f66a62856 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2636,7 +2636,7 @@ static unsigned hub_is_wusb(struct usb_hub *hub)
#define SET_ADDRESS_TRIES 2
#define GET_DESCRIPTOR_TRIES 2
#define SET_CONFIG_TRIES (2 * (use_both_schemes + 1))
-#define USE_NEW_SCHEME(i) ((i) / 2 == (int)old_scheme_first)
+#define USE_NEW_SCHEME(i, scheme) ((i) / 2 == (int)scheme)
#define HUB_ROOT_RESET_TIME 60 /* times are in msec */
#define HUB_SHORT_RESET_TIME 10
@@ -2651,12 +2651,16 @@ static unsigned hub_is_wusb(struct usb_hub *hub)
* enumeration failures, so disable this enumeration scheme for USB3
* devices.
*/
-static bool use_new_scheme(struct usb_device *udev, int retry)
+static bool use_new_scheme(struct usb_device *udev, int retry,
+ struct usb_port *port_dev)
{
+ int old_scheme_first_port =
+ port_dev->quirks & USB_PORT_QUIRK_OLD_SCHEME;
+
if (udev->speed >= USB_SPEED_SUPER)
return false;
- return USE_NEW_SCHEME(retry);
+ return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first);
}
/* Is a USB 3.0 port in the Inactive or Compliance Mode state?
@@ -4392,6 +4396,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
{
struct usb_device *hdev = hub->hdev;
struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
+ struct usb_port *port_dev = hub->ports[port1 - 1];
int retries, operations, retval, i;
unsigned delay = HUB_SHORT_RESET_TIME;
enum usb_device_speed oldspeed = udev->speed;
@@ -4513,7 +4518,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
for (retries = 0; retries < GET_DESCRIPTOR_TRIES; (++retries, msleep(100))) {
bool did_new_scheme = false;
- if (use_new_scheme(udev, retry_counter)) {
+ if (use_new_scheme(udev, retry_counter, port_dev)) {
struct usb_device_descriptor *buf;
int r = 0;
diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 4dc769ee9c740..4accfb63f7dcb 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -98,6 +98,7 @@ struct usb_port {
struct mutex status_lock;
u32 over_current_count;
u8 portnum;
+ u32 quirks;
unsigned int is_superspeed:1;
unsigned int usb3_lpm_u1_permit:1;
unsigned int usb3_lpm_u2_permit:1;
diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 6979bde87d310..4a21431953953 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -50,6 +50,28 @@ static ssize_t over_current_count_show(struct device *dev,
}
static DEVICE_ATTR_RO(over_current_count);
+static ssize_t quirks_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct usb_port *port_dev = to_usb_port(dev);
+
+ return sprintf(buf, "%08x\n", port_dev->quirks);
+}
+
+static ssize_t quirks_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct usb_port *port_dev = to_usb_port(dev);
+ u32 value;
+
+ if (kstrtou32(buf, 16, &value))
+ return -EINVAL;
+
+ port_dev->quirks = value;
+ return count;
+}
+static DEVICE_ATTR_RW(quirks);
+
static ssize_t usb3_lpm_permit_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -118,6 +140,7 @@ static DEVICE_ATTR_RW(usb3_lpm_permit);
static struct attribute *port_dev_attrs[] = {
&dev_attr_connect_type.attr,
+ &dev_attr_quirks.attr,
&dev_attr_over_current_count.attr,
NULL,
};
diff --git a/include/linux/usb.h b/include/linux/usb.h
index beffceec49158..2ade17992ed66 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -489,6 +489,13 @@ enum usb_port_connect_type {
USB_PORT_NOT_USED,
};
+/*
+ * USB port quirks.
+ */
+
+/* For the given port, prefer the old (faster) enumeration scheme. */
+#define USB_PORT_QUIRK_OLD_SCHEME BIT(0)
+
/*
* USB 2.0 Link Power Management (LPM) parameters.
*/
--
2.17.0.921.gf22659ad46-goog
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