usb: hub: Per-port setting to use old enumeration scheme

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@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index c6e9b30f05b1347cef57f4f5709f39cf55a1a2b5..a31a66d62cbbaa938f6f9770605d1ab4f0364fa7 100644 (file)
--- 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@chromium.org>
+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@skidata.com>

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index c2d993d3816f0c49261ba0b46cd6cadf288b5a34..f900f66a62856c1da8b42f566961a732cbd8133e 100644 (file)
--- 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 4dc769ee9c7402a2da8aa65d7c9b251c003587d0..4accfb63f7dcbddf77c407bb46d84be2d33a3118 100644 (file)
--- 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 6979bde87d31087f4022c5d06168977048378464..4a21431953953d5b52b467a107a04c5f8198cf19 100644 (file)
--- 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 beffceec491585b7b16670564c24be2f65fe30fe..2ade17992ed661d9311763ecf06ba4a9d0e6a745 100644 (file)
--- 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.
  */