ARM: tegra: Fix hang on reboot

This seems to be a regression in 2.6.37.

We cannot use writel() here since the resulting wmb() calls l2x0_cache_sync()
which uses a spinlock and L1 cache may be off at this point.

http://lists.infradead.org/pipermail/linux-arm-kernel/2011-February/041909.html

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Colin Cross <ccross@android.com>

arch/arm/mach-tegra/common.c

@@ -39,9 +39,10 @@ void tegra_assert_system_reset(char mode, const char *cmd)
 	void __iomem *reset = IO_ADDRESS(TEGRA_CLK_RESET_BASE + 0x04);
 	u32 reg;
 
-	reg = readl(reset);
+	/* use *_related to avoid spinlock since caches are off */
+	reg = readl_relaxed(reset);
 	reg |= 0x04;
-	writel(reg, reset);
+	writel_relaxed(reg, reset);
 }
 
 static __initdata struct tegra_clk_init_table common_clk_init_table[] = {