[U-Boot] [PATCH] usb: ehci-omap: Don't softreset USB High-speed Host (UHH) Module

[Roger Quadros]

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 at ti.com>
---
 drivers/usb/host/ehci-omap.c |   27 +++++++++++++++------------
 1 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/host/ehci-omap.c b/drivers/usb/host/ehci-omap.c
index 086c697..0f6ad29 100644
--- a/drivers/usb/host/ehci-omap.c
+++ b/drivers/usb/host/ehci-omap.c
@@ -42,18 +42,21 @@ 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;
 }
 
-- 
1.7.4.1