svn commit: r276249 - head/sys/arm/ti/am335x

[Luiz Otavio O Souza]

Author: loos
Date: Fri Dec 26 17:45:49 2014
New Revision: 276249
URL: https://svnweb.freebsd.org/changeset/base/276249

Log:
  Fix the musb initialization sequence on AM335x.
  
  According to http://e2e.ti.com/support/arm/sitara_arm/f/791/t/210729 the
  USB reset pulse has an undocumented duration of 200ns and during this
  period the module must not be acessed.
  
  We wait for 100us to take into account for some imprecision of the early
  DELAY() loop.
  
  This fixes the eventual 'External Non-Linefetch Abort (S)' that happens at
  boot while resetting the musb subsystem.
  
  While here, enable the USB subsystem clock before the first access.
  
  Discussed with: 	ian, adrian
  MFC after:		2 weeks

Modified:
  head/sys/arm/ti/am335x/am335x_usbss.c

Modified: head/sys/arm/ti/am335x/am335x_usbss.c
==============================================================================
--- head/sys/arm/ti/am335x/am335x_usbss.c	Fri Dec 26 15:04:03 2014	(r276248)
+++ head/sys/arm/ti/am335x/am335x_usbss.c	Fri Dec 26 17:45:49 2014	(r276249)
@@ -288,21 +288,30 @@ musbotg_attach(device_t dev)
 		return (ENXIO);
 	}
 
+	/* Enable device clocks. */
+	ti_prcm_clk_enable(MUSB0_CLK);
+
 	/*
-	 * Reset USBSS, USB0 and USB1
+	 * Reset USBSS, USB0 and USB1.
+	 * The registers of USB subsystem must not be accessed while the
+	 * reset pulse is active (200ns).
 	 */
+	USBSS_WRITE4(sc, USBSS_SYSCONFIG, USBSS_SYSCONFIG_SRESET);
+	DELAY(100);
+	i = 10;
+	while (USBSS_READ4(sc, USBSS_SYSCONFIG) & USBSS_SYSCONFIG_SRESET) {
+		DELAY(100);
+		if (i-- == 0) {
+			device_printf(dev, "reset timeout.\n");
+			return (ENXIO);
+		}
+	}
+
+	/* Read the module revision. */
 	rev = USBSS_READ4(sc, USBSS_REVREG);
 	device_printf(dev, "TI AM335X USBSS v%d.%d.%d\n",
 	    (rev >> 8) & 7, (rev >> 6) & 3, rev & 63);
 
-	ti_prcm_clk_enable(MUSB0_CLK);
-
-	USBSS_WRITE4(sc, USBSS_SYSCONFIG,
-	    USBSS_SYSCONFIG_SRESET);
-	while (USBSS_READ4(sc, USBSS_SYSCONFIG) &
-	    USBSS_SYSCONFIG_SRESET)
-		;
-
 	err = bus_setup_intr(dev, sc->sc_irq_res[0],
 	    INTR_TYPE_BIO | INTR_MPSAFE,
 	    NULL, (driver_intr_t *)musbotg_usbss_interrupt, sc,