usb: ehci-omap: Don't softreset USB High-speed Host (UHH) Module

Fixes NFS root problems with Beagle (3530 ES1.0) when used with
external USB-ethernet adapter and "USB start" command used within
u-boot.

Soft resetting the UHH module causes instability issues on
all OMAPs so we just avoid it.

See OMAP36xx Errata
  i571: USB host EHCI may stall when entering smart-standby mode
  i660: USBHOST Configured In Smart-Idle Can Lead To a Deadlock

On OMAP4/5, soft-resetting the UHH module can put it into
Smart-Idle mode and lead to a deadlock.

On OMAP3 this doesn't seem to be the case but still instabilities
are observed on beagle (3530 ES1.0) if soft-reset is used.
 e.g. NFS root failures with Linux kernel.

Signed-off-by: Roger Quadros <rogerq@ti.com>

diff --git a/drivers/usb/host/ehci-omap.c b/drivers/usb/host/ehci-omap.c
index a47e078f62a14e8b107c8b3859b4776b4a4197ff..032d5e5ec25b327ce85fda684c1aac4563304c9b 100644 (file)
--- a/drivers/usb/host/ehci-omap.c
+++ b/drivers/usb/host/ehci-omap.c
@@ -28,18 +28,21 @@ static struct omap_ehci *const ehci = (struct omap_ehci *)OMAP_EHCI_BASE;
 
 static int omap_uhh_reset(void)
 {
-       unsigned long init = get_timer(0);
-
-       /* perform UHH soft reset, and wait until reset is complete */
-       writel(OMAP_UHH_SYSCONFIG_SOFTRESET, &uhh->sysc);
-
-       /* Wait for UHH reset to complete */
-       while (!(readl(&uhh->syss) & OMAP_UHH_SYSSTATUS_EHCI_RESETDONE))
-               if (get_timer(init) > CONFIG_SYS_HZ) {
-                       debug("OMAP UHH error: timeout resetting ehci\n");
-                       return -EL3RST;
-               }
-
+/*
+ * Soft resetting the UHH module causes instability issues on
+ * all OMAPs so we just avoid it.
+ *
+ * See OMAP36xx Errata
+ *  i571: USB host EHCI may stall when entering smart-standby mode
+ *  i660: USBHOST Configured In Smart-Idle Can Lead To a Deadlock
+ *
+ * On OMAP4/5, soft-resetting the UHH module will put it into
+ * Smart-Idle mode and lead to a deadlock.
+ *
+ * On OMAP3, this doesn't seem to be the case but still instabilities
+ * are observed on beagle (3530 ES1.0) if soft-reset is used.
+ * e.g. NFS root failures with Linux kernel.
+ */
        return 0;
 }