[PATCH] ARM: mvebu: Enable MBUS error propagation

[Chris Packham]

U-boot disables MBUS error propagation for Armada-385. The effect of
this on the kernel is that any access to a mapped but inaccessible
address causes the system to hang.

By enabling MBUS error propagation the kernel can raise a Bus Error and
panic to restart the system.

Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
---

Notes:
    We've encountered an issue where rogue accesses to PCI-e space cause an
    Armada-385 system to lockup. We've found that enabling MBUS error
    propagation lets us get a bus error which at least gives us a panic to
    help identify what was accessed.
    
    U-boot clears the IO Err Prop Enable Bit[1] but so far no-one seems to
    know why.
    
    I wasn't sure where to put this code. There is similar code for kirwood
    in the equivalent dt_init function. On Armada-XP the register is part of
    the Core Coherency Fabric block (for A385 it's documented as part of the
    CCF block).
    
    --
    [1] - https://gitlab.denx.de/u-boot/u-boot/blob/master/arch/arm/mach-mvebu/cpu.c#L489

 arch/arm/boot/dts/armada-38x.dtsi |  5 +++++
 arch/arm/mach-mvebu/board-v7.c    | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/arch/arm/boot/dts/armada-38x.dtsi b/arch/arm/boot/dts/armada-38x.dtsi
index 3f4bb44d85f0..3214c67433eb 100644
--- a/arch/arm/boot/dts/armada-38x.dtsi
+++ b/arch/arm/boot/dts/armada-38x.dtsi
@@ -386,6 +386,11 @@
 				      <0x20250 0x8>;
 			};
 
+			ioerrc: io-err-control@20200 {
+				compatible = "marvell,io-err-control";
+				reg = <0x20200 0x4>;
+			};
+
 			mpic: interrupt-controller@20a00 {
 				compatible = "marvell,mpic";
 				reg = <0x20a00 0x2d0>, <0x21070 0x58>;
diff --git a/arch/arm/mach-mvebu/board-v7.c b/arch/arm/mach-mvebu/board-v7.c
index d2df5ef9382b..fb7718386ef9 100644
--- a/arch/arm/mach-mvebu/board-v7.c
+++ b/arch/arm/mach-mvebu/board-v7.c
@@ -138,10 +138,36 @@ static void __init i2c_quirk(void)
 	}
 }
 
+#define MBUS_ERR_PROP_EN BIT(8)
+
+/*
+ * U-boot disables MBUS error propagation. Re-enable it so we
+ * can handle them as Bus Errors.
+ */
+static void __init enable_mbus_error_propagation(void)
+{
+	struct device_node *np =
+		of_find_compatible_node(NULL, NULL, "marvell,io-err-control");
+
+	if (np) {
+		void __iomem *reg;
+
+		reg = of_iomap(np, 0);
+		if (reg) {
+			u32 val;
+
+			val = readl_relaxed(reg);
+			writel_relaxed(val | MBUS_ERR_PROP_EN, reg);
+		}
+		of_node_put(np);
+	}
+}
+
 static void __init mvebu_dt_init(void)
 {
 	if (of_machine_is_compatible("marvell,armadaxp"))
 		i2c_quirk();
+	enable_mbus_error_propagation();
 }
 
 static void __init armada_370_xp_dt_fixup(void)
@@ -191,6 +217,7 @@ DT_MACHINE_START(ARMADA_38X_DT, "Marvell Armada 380/385 (Device Tree)")
 	.l2c_aux_val	= 0,
 	.l2c_aux_mask	= ~0,
 	.init_irq       = mvebu_init_irq,
+	.init_machine	= mvebu_dt_init,
 	.restart	= mvebu_restart,
 	.dt_compat	= armada_38x_dt_compat,
 MACHINE_END
-- 
2.24.0