usb: musb: SW workaround for USB host issue

For snowball in HOST mode, the eye diagram is facing high distortion
in high speed use cases. This patch allows the user to use an
external charge pump instead of the internal one to generate
the Vbus voltage. This can be done by setting a sysfs entry.

The external VBUS is OFF by default and can be made ON by setting
the sysfs entry inorder to enumerate high speed devices.

Signed-off-by: supriya karanth <supriya.karanth@stericsson.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index 1ab2fd8c3e9..2923752b858 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -1767,10 +1767,45 @@ musb_srp_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR(srp, 0644, NULL, musb_srp_store);
 
+static ssize_t
+ux500_set_extvbus(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t n)
+{
+	struct musb_hdrc_platform_data *plat = dev->platform_data;
+	unsigned short	extvbus;
+
+	if (sscanf(buf, "%hu", &extvbus) != 1
+			|| ((extvbus != 1) && (extvbus != 0))) {
+		dev_err(dev, "Invalid value EXTVBUS must be 1 or 0\n");
+		return -EINVAL;
+	}
+
+	plat->extvbus = extvbus;
+
+	return n;
+}
+
+static ssize_t
+ux500_get_extvbus(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct musb_hdrc_platform_data *plat = dev->platform_data;
+	int		extvbus;
+
+	/* FIXME get_vbus_status() is normally #defined as false...
+	 * and is effectively TUSB-specific.
+	 */
+	extvbus = plat->extvbus;
+
+	return sprintf(buf, "EXTVBUS is %s\n",
+			extvbus ? "on" : "off");
+}
+static DEVICE_ATTR(extvbus, 0644, ux500_get_extvbus, ux500_set_extvbus);
+
 static struct attribute *musb_attributes[] = {
 	&dev_attr_mode.attr,
 	&dev_attr_vbus.attr,
 	&dev_attr_srp.attr,
+	&dev_attr_extvbus.attr,
 	NULL
 };