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Subject[PATCH 2/4] ARM: sunxi: mc-smp: Use DT enable-method for sun9i A80 SMP
Date
Instead of having an early init function check the machine compatible
and installing multi-cluster SMP support for the A80 if it matches,
use a new cpu enable-method string. This makes the platform support
future proof in case anyone manages to add PSCI support.

The original init code for the SMP support is changed into the
.prepare_cpus callback in the smp_operations structure. Instead of
panicing when resources are missing like on some platforms, our code
merely guards against engaging SMP or CPU hotplug and returns an error.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
Documentation/devicetree/bindings/arm/cpus.txt | 1 +
arch/arm/mach-sunxi/mc_smp.c | 21 ++++++++++++++++++++-
2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
index f4a777039f03..76655d0d67c2 100644
--- a/Documentation/devicetree/bindings/arm/cpus.txt
+++ b/Documentation/devicetree/bindings/arm/cpus.txt
@@ -198,6 +198,7 @@ described below.
"actions,s500-smp"
"allwinner,sun6i-a31"
"allwinner,sun8i-a23"
+ "allwinner,sun9i-a80-smp"
"amlogic,meson8-smp"
"amlogic,meson8b-smp"
"arm,realview-smp"
diff --git a/arch/arm/mach-sunxi/mc_smp.c b/arch/arm/mach-sunxi/mc_smp.c
index 9db6c4ed5861..86e90b038555 100644
--- a/arch/arm/mach-sunxi/mc_smp.c
+++ b/arch/arm/mach-sunxi/mc_smp.c
@@ -690,7 +690,26 @@ static int __init sunxi_mc_smp_init(void)
struct resource res;
int ret;

- if (!of_machine_is_compatible("allwinner,sun9i-a80"))
+ /*
+ * Don't bother checking the "cpus" node, as an enable-method
+ * property in that node is undocumented.
+ */
+ node = of_cpu_device_node_get(0);
+ if (!node)
+ return -ENODEV;
+
+ /*
+ * We can't actually use the enable-method magic in the kernel.
+ * Our loopback / trampoline code uses the CPU suspend framework,
+ * which requires the identity mapping be available. It would not
+ * yet be available if we used the .init_cpus or .prepare_cpus
+ * callbacks in smp_operations, which we would use if we were to
+ * use CPU_METHOD_OF_DECLARE
+ */
+ ret = of_property_match_string(node, "enable-method",
+ "allwinner,sun9i-a80-smp");
+ of_node_put(node);
+ if (ret)
return -ENODEV;

if (!sunxi_mc_smp_cpu_table_init())
--
2.16.2
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