On Fri, Jul 06, 2018 at 12:43:52PM +0100, Mark Rutland wrote:

Please see the devicetree spec [1], section 2.3.4. Valid values are:

* "okay" // equivalent to no status property present
* "disabled"
* "fail"
* "fail-sss"

Nice tip, thx.

I'm a bit confused. You write (1 << cpu) into cv<29, 0>, to enable a
particular CPU, so I assume that bit uniquely identifies a CPU,

Yes, you're right and cr<29, 0>'s bit uniquely identifies a cpu.

and
therefore the reg is some unique ID for the CPU.

static int csky_of_cpu(struct device_node *node)
{
	const char *status;

	if (of_property_read_string(node, "status", &status))
		status = "okay";

	if (strcmp(status, "disabled") == 0)
		goto error;

	return 1;
error:
	return 0;
}

void __init setup_smp(void)
{
	struct device_node *node = NULL;
	int i = 0;

	while ((node = of_find_node_by_type(node, "cpu"))) {
		if (!csky_of_cpu(node))
			continue;

		set_cpu_possible(i, true);
		set_cpu_present(i, true);

		i++;
	}
}
Hmm?

No <reg> in next version patch, it's no use.

I see.

Is this SMP bringup mechanism architectual, or are you likely to need
another mechanism to turn on CPUs on future chips?

It's the only SMP bringup mechanism architectual for C-SKY SMP. There is
no another way in future and SOC vendor couldn't change it.

You probably want to use an enable-method property to describe this.

No, thx.

 Guo Ren