[RFC/PATCHv2 2/5] ARM: mvebu: use dt_fixup to provide fallback for enable-method

[Chris Packham]

When the device tree doesn't define an enable-method insert a property
into the flattened device tree. arm_dt_init_cpu_maps() will then parse
this an set smp_ops appropriately. Now that we have this fallback it is
no longer necessary to set .smp in the DT_MACHINE definition.
Additionally Armada 370, which is a single core device, no longer has any
smp operations defined.

Signed-off-by: Chris Packham <chris.packham at alliedtelesis.co.nz>
---
As Arnd and Maxime suggested this replaces the unconditional setting of
smp_ops[1] with a fixup that inserts an appropriate property in the
device-tree if needed. It turned out not to be terribly tricky to
implement that checked each possible CPU node. One assumption I've made
is that the cpu nodes are numbered contiguously but that seems to be
reasonable.

[1] - http://lists.infradead.org/pipermail/linux-arm-kernel/2014-December/309766.html

 arch/arm/mach-mvebu/board-v7.c | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-mvebu/board-v7.c b/arch/arm/mach-mvebu/board-v7.c
index d0d39f1..08eb6a9 100644
--- a/arch/arm/mach-mvebu/board-v7.c
+++ b/arch/arm/mach-mvebu/board-v7.c
@@ -17,6 +17,8 @@
 #include <linux/clk-provider.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
+#include <linux/of_fdt.h>
+#include <linux/libfdt.h>
 #include <linux/io.h>
 #include <linux/clocksource.h>
 #include <linux/dma-mapping.h>
@@ -198,6 +200,44 @@ static void __init mvebu_dt_init(void)
 	of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
 }
 
+static void __init armada_370_xp_dt_fixup(void)
+{
+	int offset, node;
+	int i, len;
+	void *prop;
+	char buffer[20];
+	unsigned long root = of_get_flat_dt_root();
+
+	if (!IS_ENABLED(CONFIG_SMP) ||
+	    !of_flat_dt_is_compatible(root, "marvell,armadaxp"))
+		return;
+
+	offset = fdt_path_offset(initial_boot_params, "/cpus");
+	if (offset < 0)
+		return;
+
+	prop = fdt_getprop(initial_boot_params, offset, "enable-method", &len);
+	if (prop)
+		return;
+
+	for (i = 0; i < NR_CPUS; i++) {
+		snprintf(buffer, sizeof(buffer), "cpu@%d", i);
+		node = fdt_subnode_offset(initial_boot_params, offset, buffer);
+		if (node < 0)
+			break;
+		prop = fdt_getprop(initial_boot_params, node,
+				   "enable-method", &len);
+		if (prop)
+			return;
+	}
+
+	pr_info("No enable-method defined. "
+		"Falling back to \"marvell,armada-xp-smp\"\n");
+
+	fdt_setprop(initial_boot_params, offset, "enable-method",
+		    "marvell,armada-xp-smp", sizeof("marvell,armada-xp-smp"));
+}
+
 static const char * const armada_370_xp_dt_compat[] = {
 	"marvell,armada-370-xp",
 	NULL,
@@ -206,11 +246,11 @@ static const char * const armada_370_xp_dt_compat[] = {
 DT_MACHINE_START(ARMADA_370_XP_DT, "Marvell Armada 370/XP (Device Tree)")
 	.l2c_aux_val	= 0,
 	.l2c_aux_mask	= ~0,
-	.smp		= smp_ops(armada_xp_smp_ops),
 	.init_machine	= mvebu_dt_init,
 	.init_irq       = mvebu_init_irq,
 	.restart	= mvebu_restart,
 	.dt_compat	= armada_370_xp_dt_compat,
+	.dt_fixup	= armada_370_xp_dt_fixup,
 MACHINE_END
 
 static const char * const armada_375_dt_compat[] = {
-- 
2.2.0.rc0