phy: cpcap-usb: Improve host vs docked mode detection

When docked to a Motorola lapdock or media dock, we're in USB A-host mode
with VBUS provided by the dock. When in regular USB A-host mode, we're
providing the VBUS. And in regular USB A-host mode we must also keep
kicking the VBUS to keep it active.

Let's wait a bit before configuring the USB PHY to allow some time between
the ID and VBUS changes. And let's add vbus_provider flag so we can detect
docked mode and regularo USB A-host mode better.

With better USB A-host mode detection, we can now also just kick the
VBUS to keep it enabled and leave out the unnecessary line muxing.

We only need to set and clear vbus_provider in the delayed work so no
locking is needed for it currently.

Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/motorola/phy-cpcap-usb.c

@@ -134,6 +134,8 @@ struct cpcap_phy_ddata {
 	struct iio_channel *id;
 	struct regulator *vusb;
 	atomic_t active;
+	unsigned int vbus_provider:1;
+	unsigned int docked:1;
 };
 
 static bool cpcap_usb_vbus_valid(struct cpcap_phy_ddata *ddata)
@@ -233,11 +235,11 @@ static void cpcap_usb_detect(struct work_struct *work)
 	if (error)
 		return;
 
-	if (s.id_ground) {
-		dev_dbg(ddata->dev, "id ground, USB host mode\n");
-		error = cpcap_usb_set_usb_mode(ddata);
-		if (error)
-			goto out_err;
+	vbus = cpcap_usb_vbus_valid(ddata);
+
+	/* We need to kick the VBUS as USB A-host */
+	if (s.id_ground && ddata->vbus_provider) {
+		dev_dbg(ddata->dev, "still in USB A-host mode, kicking VBUS\n");
 
 		cpcap_usb_try_musb_mailbox(ddata, MUSB_ID_GROUND);
 
@@ -251,29 +253,68 @@ static void cpcap_usb_detect(struct work_struct *work)
 		return;
 	}
 
-	error = regmap_update_bits(ddata->reg, CPCAP_REG_USBC3,
-				   CPCAP_BIT_VBUSSTBY_EN |
-				   CPCAP_BIT_VBUSEN_SPI, 0);
+	if (vbus && s.id_ground && ddata->docked) {
+		dev_dbg(ddata->dev, "still docked as A-host, signal ID down\n");
+
+		cpcap_usb_try_musb_mailbox(ddata, MUSB_ID_GROUND);
+
+		return;
+	}
+
+	/* No VBUS needed with docks */
+	if (vbus && s.id_ground && !ddata->vbus_provider) {
+		dev_dbg(ddata->dev, "connected to a dock\n");
+
+		ddata->docked = true;
+
+		error = cpcap_usb_set_usb_mode(ddata);
 		if (error)
 			goto out_err;
 
-	vbus = cpcap_usb_vbus_valid(ddata);
+		cpcap_usb_try_musb_mailbox(ddata, MUSB_ID_GROUND);
 
-	if (vbus) {
-		/* Are we connected to a docking station with vbus? */
-		if (s.id_ground) {
-			dev_dbg(ddata->dev, "connected to a dock\n");
+		/*
+		 * Force check state again after musb has reoriented,
+		 * otherwise devices won't enumerate after loading PHY
+		 * driver.
+		 */
+		schedule_delayed_work(&ddata->detect_work,
+				      msecs_to_jiffies(1000));
+
+		return;
+	}
+
+	if (s.id_ground && !ddata->docked) {
+		dev_dbg(ddata->dev, "id ground, USB host mode\n");
+
+		ddata->vbus_provider = true;
 
-			/* No VBUS needed with docks */
 		error = cpcap_usb_set_usb_mode(ddata);
 		if (error)
 			goto out_err;
+
 		cpcap_usb_try_musb_mailbox(ddata, MUSB_ID_GROUND);
 
+		error = regmap_update_bits(ddata->reg, CPCAP_REG_USBC3,
+					   CPCAP_BIT_VBUSSTBY_EN |
+					   CPCAP_BIT_VBUSEN_SPI,
+					   CPCAP_BIT_VBUSEN_SPI);
+		if (error)
+			goto out_err;
+
 		return;
 	}
 
+	error = regmap_update_bits(ddata->reg, CPCAP_REG_USBC3,
+				   CPCAP_BIT_VBUSSTBY_EN |
+				   CPCAP_BIT_VBUSEN_SPI, 0);
+	if (error)
+		goto out_err;
+
+	vbus = cpcap_usb_vbus_valid(ddata);
+
 	/* Otherwise assume we're connected to a USB host */
+	if (vbus) {
 		dev_dbg(ddata->dev, "connected to USB host\n");
 		error = cpcap_usb_set_usb_mode(ddata);
 		if (error)
@@ -283,6 +324,8 @@ static void cpcap_usb_detect(struct work_struct *work)
 		return;
 	}
 
+	ddata->vbus_provider = false;
+	ddata->docked = false;
 	cpcap_usb_try_musb_mailbox(ddata, MUSB_VBUS_OFF);
 
 	/* Default to debug UART mode */