smp.c

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2
 3/*
 4 * SMP support functions for Microwatt
 5 * Copyright 2025 Paul Mackerras <paulus@ozlabs.org>
 6 */
 7
 8#include <linux/kernel.h>
 9#include <linux/smp.h>
10#include <linux/io.h>
11#include <asm/early_ioremap.h>
12#include <asm/ppc-opcode.h>
13#include <asm/reg.h>
14#include <asm/smp.h>
15#include <asm/xics.h>
16
17#include "microwatt.h"
18
19static void __init microwatt_smp_probe(void)
20{
21	xics_smp_probe();
22}
23
24static void microwatt_smp_setup_cpu(int cpu)
25{
26	if (cpu != 0)
27		xics_setup_cpu();
28}
29
30static struct smp_ops_t microwatt_smp_ops = {
31	.probe		= microwatt_smp_probe,
32	.message_pass	= NULL,		/* Use smp_muxed_ipi_message_pass */
33	.kick_cpu	= smp_generic_kick_cpu,
34	.setup_cpu	= microwatt_smp_setup_cpu,
35};
36
37/* XXX get from device tree */
38#define SYSCON_BASE	0xc0000000
39#define SYSCON_LENGTH	0x100
40
41#define SYSCON_CPU_CTRL	0x58
42
43void __init microwatt_init_smp(void)
44{
45	volatile unsigned char __iomem *syscon;
46	int ncpus;
47	int timeout;
48
49	syscon = early_ioremap(SYSCON_BASE, SYSCON_LENGTH);
50	if (syscon == NULL) {
51		pr_err("Failed to map SYSCON\n");
52		return;
53	}
54	ncpus = (readl(syscon + SYSCON_CPU_CTRL) >> 8) & 0xff;
55	if (ncpus < 2)
56		goto out;
57
58	smp_ops = &microwatt_smp_ops;
59
60	/*
61	 * Write two instructions at location 0:
62	 * mfspr r3, PIR
63	 * b __secondary_hold
64	 */
65	*(unsigned int *)KERNELBASE = PPC_RAW_MFSPR(3, SPRN_PIR);
66	*(unsigned int *)(KERNELBASE+4) = PPC_RAW_BRANCH(&__secondary_hold - (char *)(KERNELBASE+4));
67
68	/* enable the other CPUs, they start at location 0 */
69	writel((1ul << ncpus) - 1, syscon + SYSCON_CPU_CTRL);
70
71	timeout = 10000;
72	while (!__secondary_hold_acknowledge) {
73		if (--timeout == 0)
74			break;
75		barrier();
76	}
77
78 out:
79	early_iounmap((void *)syscon, SYSCON_LENGTH);
80}