6 files changed, 207 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/microwatt/Kconfig b/arch/powerpc/platforms/microwatt/Kconfig
new file mode 100644
index 000000000000..cb2aff635bb0
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/Kconfig
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+config PPC_MICROWATT
+	depends on PPC_BOOK3S_64
+	bool "Microwatt SoC platform"
+	select PPC_XICS
+	select PPC_ICS_NATIVE
+	select PPC_ICP_NATIVE
+	select PPC_UDBG_16550
+	select COMMON_CLK
+	help
+          This option enables support for FPGA-based Microwatt implementations.
+
diff --git a/arch/powerpc/platforms/microwatt/Makefile b/arch/powerpc/platforms/microwatt/Makefile
new file mode 100644
index 000000000000..d973b2ab4042
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/Makefile
@@ -0,0 +1,2 @@
+obj-y	+= setup.o rng.o
+obj-$(CONFIG_SMP) += smp.o
diff --git a/arch/powerpc/platforms/microwatt/microwatt.h b/arch/powerpc/platforms/microwatt/microwatt.h
new file mode 100644
index 000000000000..891aa2800768
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/microwatt.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _MICROWATT_H
+#define _MICROWATT_H
+
+void microwatt_rng_init(void);
+void microwatt_init_smp(void);
+
+#endif /* _MICROWATT_H */
diff --git a/arch/powerpc/platforms/microwatt/rng.c b/arch/powerpc/platforms/microwatt/rng.c
new file mode 100644
index 000000000000..8ece87d005c8
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/rng.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Derived from arch/powerpc/platforms/powernv/rng.c, which is:
+ * Copyright 2013, Michael Ellerman, IBM Corporation.
+ */
+
+#define pr_fmt(fmt)	"microwatt-rng: " fmt
+
+#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <asm/archrandom.h>
+#include <asm/cputable.h>
+#include <asm/machdep.h>
+#include "microwatt.h"
+
+#define DARN_ERR 0xFFFFFFFFFFFFFFFFul
+
+static int microwatt_get_random_darn(unsigned long *v)
+{
+	unsigned long val;
+
+	/* Using DARN with L=1 - 64-bit conditioned random number */
+	asm volatile(PPC_DARN(%0, 1) : "=r"(val));
+
+	if (val == DARN_ERR)
+		return 0;
+
+	*v = val;
+
+	return 1;
+}
+
+void __init microwatt_rng_init(void)
+{
+	unsigned long val;
+	int i;
+
+	for (i = 0; i < 10; i++) {
+		if (microwatt_get_random_darn(&val)) {
+			ppc_md.get_random_seed = microwatt_get_random_darn;
+			return;
+		}
+	}
+}
diff --git a/arch/powerpc/platforms/microwatt/setup.c b/arch/powerpc/platforms/microwatt/setup.c
new file mode 100644
index 000000000000..6af2ccef736c
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/setup.c
@@ -0,0 +1,61 @@
+/*
+ * Microwatt FPGA-based SoC platform setup code.
+ *
+ * Copyright 2020 Paul Mackerras (paulus@ozlabs.org), IBM Corp.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/stddef.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+
+#include <asm/machdep.h>
+#include <asm/time.h>
+#include <asm/xics.h>
+#include <asm/udbg.h>
+
+#include "microwatt.h"
+
+static void __init microwatt_init_IRQ(void)
+{
+	xics_init();
+}
+
+static int __init microwatt_populate(void)
+{
+	return of_platform_default_populate(NULL, NULL, NULL);
+}
+machine_arch_initcall(microwatt, microwatt_populate);
+
+static int __init microwatt_probe(void)
+{
+	/* Main reason for having this is to start the other CPU(s) */
+	if (IS_ENABLED(CONFIG_SMP))
+		microwatt_init_smp();
+	return 1;
+}
+
+static void __init microwatt_setup_arch(void)
+{
+	microwatt_rng_init();
+}
+
+static void microwatt_idle(void)
+{
+	if (!prep_irq_for_idle_irqsoff())
+		return;
+
+	__asm__ __volatile__ ("wait");
+}
+
+define_machine(microwatt) {
+	.name			= "microwatt",
+	.compatible		= "microwatt-soc",
+	.probe			= microwatt_probe,
+	.init_IRQ		= microwatt_init_IRQ,
+	.setup_arch		= microwatt_setup_arch,
+	.progress		= udbg_progress,
+	.power_save		= microwatt_idle,
+};
diff --git a/arch/powerpc/platforms/microwatt/smp.c b/arch/powerpc/platforms/microwatt/smp.c
new file mode 100644
index 000000000000..7dbf2ca73d47
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/smp.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/*
+ * SMP support functions for Microwatt
+ * Copyright 2025 Paul Mackerras <paulus@ozlabs.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <linux/io.h>
+#include <asm/early_ioremap.h>
+#include <asm/ppc-opcode.h>
+#include <asm/reg.h>
+#include <asm/smp.h>
+#include <asm/xics.h>
+
+#include "microwatt.h"
+
+static void __init microwatt_smp_probe(void)
+{
+	xics_smp_probe();
+}
+
+static void microwatt_smp_setup_cpu(int cpu)
+{
+	if (cpu != 0)
+		xics_setup_cpu();
+}
+
+static struct smp_ops_t microwatt_smp_ops = {
+	.probe		= microwatt_smp_probe,
+	.message_pass	= NULL,		/* Use smp_muxed_ipi_message_pass */
+	.kick_cpu	= smp_generic_kick_cpu,
+	.setup_cpu	= microwatt_smp_setup_cpu,
+};
+
+/* XXX get from device tree */
+#define SYSCON_BASE	0xc0000000
+#define SYSCON_LENGTH	0x100
+
+#define SYSCON_CPU_CTRL	0x58
+
+void __init microwatt_init_smp(void)
+{
+	volatile unsigned char __iomem *syscon;
+	int ncpus;
+	int timeout;
+
+	syscon = early_ioremap(SYSCON_BASE, SYSCON_LENGTH);
+	if (syscon == NULL) {
+		pr_err("Failed to map SYSCON\n");
+		return;
+	}
+	ncpus = (readl(syscon + SYSCON_CPU_CTRL) >> 8) & 0xff;
+	if (ncpus < 2)
+		goto out;
+
+	smp_ops = &microwatt_smp_ops;
+
+	/*
+	 * Write two instructions at location 0:
+	 * mfspr r3, PIR
+	 * b __secondary_hold
+	 */
+	*(unsigned int *)KERNELBASE = PPC_RAW_MFSPR(3, SPRN_PIR);
+	*(unsigned int *)(KERNELBASE+4) = PPC_RAW_BRANCH(&__secondary_hold - (char *)(KERNELBASE+4));
+
+	/* enable the other CPUs, they start at location 0 */
+	writel((1ul << ncpus) - 1, syscon + SYSCON_CPU_CTRL);
+
+	timeout = 10000;
+	while (!__secondary_hold_acknowledge) {
+		if (--timeout == 0)
+			break;
+		barrier();
+	}
+
+ out:
+	early_iounmap((void *)syscon, SYSCON_LENGTH);
+}