USB: ehci-dbgp: errata for EHCI debug controller initialization

On some EHCI usb debug controllers, the EHCI debug device will fail to
be seen after a port reset, after a warm reset.  Two options exist to
get the device to initialize correctly.

Option 1 is to unplug and plug in the device.

Option 2 is to use the EHCI port test to get the usb debug device to
start talking again.  At that point the debug controller port reset
will succeed.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
CC: dbrownell@users.sourceforge.net
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/early/ehci-dbgp.c

@@ -478,10 +478,13 @@ int dbgp_external_startup(void)
 	int devnum;
 	struct usb_debug_descriptor dbgp_desc;
 	int ret;
-	u32 ctrl, portsc;
+	u32 ctrl, portsc, cmd;
 	int dbg_port = dbgp_phys_port;
 	int tries = 3;
+	int reset_port_tries = 1;
+	int try_hard_once = 1;
 
+try_port_reset_again:
 	ret = dbgp_ehci_startup();
 	if (ret)
 		return ret;
@@ -490,6 +493,24 @@ int dbgp_external_startup(void)
 	ret = ehci_wait_for_port(dbg_port);
 	if (ret < 0) {
 		portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
+		if (!(portsc & PORT_CONNECT) && try_hard_once) {
+			/* Last ditch effort to try to force enable
+			 * the debug device by using the packet test
+			 * ehci command to try and wake it up. */
+			try_hard_once = 0;
+			cmd = readl(&ehci_regs->command);
+			cmd &= ~CMD_RUN;
+			writel(cmd, &ehci_regs->command);
+			portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
+			portsc |= PORT_TEST_PKT;
+			writel(portsc, &ehci_regs->port_status[dbg_port - 1]);
+			dbgp_ehci_status("Trying to force debug port online");
+			mdelay(50);
+			dbgp_ehci_controller_reset();
+			goto try_port_reset_again;
+		} else if (reset_port_tries--) {
+			goto try_port_reset_again;
+		}
 		dbgp_printk("No device found in debug port\n");
 		return -EIO;
 	}

include/linux/usb/ehci_def.h

@@ -105,6 +105,7 @@ struct ehci_regs {
 #define PORT_WKDISC_E	(1<<21)		/* wake on disconnect (enable) */
 #define PORT_WKCONN_E	(1<<20)		/* wake on connect (enable) */
 /* 19:16 for port testing */
+#define PORT_TEST_PKT	(0x4<<16)	/* Port Test Control - packet test */
 #define PORT_LED_OFF	(0<<14)
 #define PORT_LED_AMBER	(1<<14)
 #define PORT_LED_GREEN	(2<<14)