[PATCH] ARM: tegra: only run PL310 init on systems with one

[swarren@wwwdotorg.org (Stephen Warren)]

From: Stephen Warren <swarren@nvidia.com>

(This is commit 8859685785bfafadf9bc922dd3a2278e59886947 upstream)

Fix tegra_init_cache() to check whether the system has a PL310 cache
before touching the PL310 registers. This prevents access to non-existent
registers on Tegra114 and later.

(When applying this to 3.10, there will be a trivial conflict, just due to
context differences, at the added include of (linux/of.h>)

(I applied and tested this backport on each of v3.10.*, v3.11.*, v3.12.*)

Cc: <stable@vger.kernel.org> # v3.10..v3.12 inclusive
Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
 arch/arm/mach-tegra/common.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm/mach-tegra/common.c b/arch/arm/mach-tegra/common.c
index 94a119a35af8..3c405f43ca39 100644
--- a/arch/arm/mach-tegra/common.c
+++ b/arch/arm/mach-tegra/common.c
@@ -22,6 +22,7 @@
 #include <linux/io.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/of.h>
 #include <linux/reboot.h>
 #include <linux/irqchip.h>
 #include <linux/clk-provider.h>
@@ -82,10 +83,20 @@ void tegra_assert_system_reset(enum reboot_mode mode, const char *cmd)
 static void __init tegra_init_cache(void)
 {
 #ifdef CONFIG_CACHE_L2X0
+	static const struct of_device_id pl310_ids[] __initconst = {
+		{ .compatible = "arm,pl310-cache",  },
+		{}
+	};
+
+	struct device_node *np;
 	int ret;
 	void __iomem *p = IO_ADDRESS(TEGRA_ARM_PERIF_BASE) + 0x3000;
 	u32 aux_ctrl, cache_type;
 
+	np = of_find_matching_node(NULL, pl310_ids);
+	if (!np)
+		return;
+
 	cache_type = readl(p + L2X0_CACHE_TYPE);
 	aux_ctrl = (cache_type & 0x700) << (17-8);
 	aux_ctrl |= 0x7C400001;
-- 
1.8.1.5