tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 = µwatt_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}