usb: imx: implement support for limiting host to full speed

This is needed when host is known to not work properly in high speed
mode.

In linux, chipidea driver supports 'maximum-speed' device tree property.
When that is set to "full-speed", driver sets PFSC bit in PORTSC
register, which disallows use of high speed mode.

This patch implements same support for barebox.

Important technical detail is that PFSC bit is cleared by port reset,
thus setting it has to be done in ehci->init() callback which is called
after ehci_reset().

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 49 insertions, 0 deletions

diff --git a/drivers/usb/core/common.c b/drivers/usb/core/common.c
index 690d5a39ea..bcbe3a155d 100644
--- a/drivers/usb/core/common.c
+++ b/drivers/usb/core/common.c
@@ -17,3 +17,15 @@ const char *usb_speed_string(enum usb_device_speed speed)
 	return speed_names[speed];
 }
 EXPORT_SYMBOL_GPL(usb_speed_string);
+
+enum usb_device_speed usb_speed_by_string(const char *string)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(speed_names); i++)
+		if (!strcmp(string, speed_names[i]))
+			return i;
+
+	return USB_SPEED_UNKNOWN;
+}
+EXPORT_SYMBOL_GPL(usb_speed_by_string);
diff --git a/drivers/usb/core/of.c b/drivers/usb/core/of.c
index fd20368424..979088ef4e 100644
--- a/drivers/usb/core/of.c
+++ b/drivers/usb/core/of.c
@@ -90,3 +90,27 @@ enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np,
 	return USBPHY_INTERFACE_MODE_UNKNOWN;
 }
 EXPORT_SYMBOL_GPL(of_usb_get_phy_mode);
+
+/**
+ * of_usb_get_maximum_speed - Get maximum speed for given device_node
+ * @np:	Pointer to the given device_node
+ *
+ * The function gets maximum speed string from property 'maximum-speed',
+ * and returns the correspondig enum usb_device_speed
+ */
+enum usb_device_speed of_usb_get_maximum_speed(struct device_node *np,
+		const char *propname)
+{
+	const char *maximum_speed;
+	int err;
+
+	if (!propname)
+		propname = "maximum-speed";
+
+	err = of_property_read_string(np, propname, &maximum_speed);
+	if (err < 0)
+		return USB_SPEED_UNKNOWN;
+
+	return usb_speed_by_string(maximum_speed);
+}
+EXPORT_SYMBOL_GPL(of_usb_get_maximum_speed);
diff --git a/drivers/usb/imx/chipidea-imx.c b/drivers/usb/imx/chipidea-imx.c
index 505f5eb35d..3e3e6a365f 100644
--- a/drivers/usb/imx/chipidea-imx.c
+++ b/drivers/usb/imx/chipidea-imx.c
@@ -51,6 +51,7 @@ struct imx_chipidea {
 static int imx_chipidea_port_init(void *drvdata)
 {
 	struct imx_chipidea *ci = drvdata;
+	uint32_t portsc;
 	int ret;
 
 	if ((ci->flags & MXC_EHCI_PORTSC_MASK) == MXC_EHCI_MODE_ULPI) {
@@ -74,6 +75,14 @@ static int imx_chipidea_port_init(void *drvdata)
 	if (ret)
 		dev_err(ci->dev, "misc init failed: %s\n", strerror(-ret));
 
+	/* PFSC bit is reset by ehci_reset(), thus have to set it not in
+	 * probe but here, after ehci_reset() is already called */
+	if (ci->flags & MXC_EHCI_PFSC) {
+		portsc = readl(ci->base + 0x184);
+		portsc |= MXC_EHCI_PFSC;
+		writel(portsc, ci->base + 0x184);
+	}
+
 	return ret;
 }
 
@@ -159,6 +168,10 @@ static int imx_chipidea_probe_dt(struct imx_chipidea *ci)
 				   "over-current-active-high", NULL))
 		ci->flags |= MXC_EHCI_OC_PIN_ACTIVE_LOW;
 
+	if (of_usb_get_maximum_speed(ci->dev->device_node, NULL) ==
+			USB_SPEED_FULL)
+		ci->flags |= MXC_EHCI_PFSC;
+
 	return 0;
 }