On Wed, Mar 18, 2015 at 6:29 PM, Maxime Ripard
[off-list ref] wrote:

On Wed, Mar 18, 2015 at 11:24:01AM +0800, Chen-Yu Tsai wrote:

quoted

The A23 is a dual Cortex-A7. Add the logic to use the IPs used to
control the CPU configuration and the CPU power so that we can
bring up secondary CPUs at boot.

Signed-off-by: Chen-Yu Tsai <redacted>
---

We can't use of_io_request_and_map() here, as it will conflict
with PRCM, and leave us without a serial console.

I think a proper way to solve this would be a syscon device or
something like the mfd-simple device posted by Arnd.

---
 Documentation/devicetree/bindings/arm/cpus.txt |  1 +
 arch/arm/mach-sunxi/platsmp.c                  | 69 ++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
index 8b9e0a95de31..40202d85b132 100644
--- a/Documentation/devicetree/bindings/arm/cpus.txt
+++ b/Documentation/devicetree/bindings/arm/cpus.txt

@@ -188,6 +188,7 @@ nodes to be present and contain the properties described below.
                      # On ARM 32-bit systems this property is optional and
                        can be one of:
                          "allwinner,sun6i-a31"
+                         "allwinner,sun8i-a23"
                          "arm,psci"
                          "brcm,brahma-b15"
                          "marvell,armada-375-smp"

diff --git a/arch/arm/mach-sunxi/platsmp.c b/arch/arm/mach-sunxi/platsmp.c
index 587b0468efcc..e8483ec79d67 100644
--- a/arch/arm/mach-sunxi/platsmp.c
+++ b/arch/arm/mach-sunxi/platsmp.c

@@ -121,3 +121,72 @@ static struct smp_operations sun6i_smp_ops __initdata = {
      .smp_boot_secondary     = sun6i_smp_boot_secondary,
 };
 CPU_METHOD_OF_DECLARE(sun6i_a31_smp, "allwinner,sun6i-a31", &sun6i_smp_ops);
+
+static void __init sun8i_smp_prepare_cpus(unsigned int max_cpus)
+{
+     struct device_node *node;
+
+     node = of_find_compatible_node(NULL, NULL, "allwinner,sun8i-a23-prcm");
+     if (!node) {
+             pr_err("Missing A23 PRCM node in the device tree\n");
+             return;
+     }
+
+     prcm_membase = of_iomap(node, 0);
+     if (!prcm_membase) {
+             pr_err("Couldn't map A23 PRCM registers\n");
+             return;
+     }
+
+     node = of_find_compatible_node(NULL, NULL,
+                                    "allwinner,sun8i-a23-cpuconfig");
+     if (!node) {
+             pr_err("Missing A23 CPU config node in the device tree\n");
+             return;
+     }
+
+     cpucfg_membase = of_iomap(node, 0);
+     if (!cpucfg_membase)
+             pr_err("Couldn't map A23 CPU config registers\n");
+
+}
+
+static int sun8i_smp_boot_secondary(unsigned int cpu,
+                                 struct task_struct *idle)
+{
+     u32 reg;
+
+     if (!(prcm_membase && cpucfg_membase))
+             return -EFAULT;
+
+     spin_lock(&cpu_lock);
+
+     /* Set CPU boot address */
+     writel(virt_to_phys(secondary_startup),
+            cpucfg_membase + CPUCFG_PRIVATE0_REG);

One question I couldn't find any answer to is that does the SMP bit is
set in secondary_startup?

I couldn't find where it was set, but it still looks like the right
thing to do, so I would expect the code to do that.

I don't see it either. The sun8i code is just the sun6i code with the
power clamps removed. And sun6i secondary_startup was removed some time
ago in commit 1146b600044d ("ARM: sunxi: fix build for THUMB2_KERNEL").

ChenYu