linux/arch/arm64/kernel/acpi_parking_protocol.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * ARM64 ACPI Parking Protocol implementation
 *
 * Authors: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
 *	    Mark Salter <msalter@redhat.com>
 */
#include <linux/acpi.h>
#include <linux/mm.h>
#include <linux/types.h>

#include <asm/cpu_ops.h>

struct parking_protocol_mailbox {
	__le32 cpu_id;
	__le32 reserved;
	__le64 entry_point;
};

struct cpu_mailbox_entry {
	struct parking_protocol_mailbox __iomem *mailbox;
	phys_addr_t mailbox_addr;
	u8 version;
	u8 gic_cpu_id;
};

static struct cpu_mailbox_entry cpu_mailbox_entries[NR_CPUS];

void __init acpi_set_mailbox_entry(int cpu,
				   struct acpi_madt_generic_interrupt *p)
{
	struct cpu_mailbox_entry *cpu_entry = &cpu_mailbox_entries[cpu];

	cpu_entry->mailbox_addr = p->parked_address;
	cpu_entry->version = p->parking_version;
	cpu_entry->gic_cpu_id = p->cpu_interface_number;
}

bool acpi_parking_protocol_valid(int cpu)
{
	struct cpu_mailbox_entry *cpu_entry = &cpu_mailbox_entries[cpu];

	return cpu_entry->mailbox_addr && cpu_entry->version;
}

static int acpi_parking_protocol_cpu_init(unsigned int cpu)
{
	pr_debug("%s: ACPI parked addr=%llx\n", __func__,
		  cpu_mailbox_entries[cpu].mailbox_addr);

	return 0;
}

static int acpi_parking_protocol_cpu_prepare(unsigned int cpu)
{
	return 0;
}

static int acpi_parking_protocol_cpu_boot(unsigned int cpu)
{
	struct cpu_mailbox_entry *cpu_entry = &cpu_mailbox_entries[cpu];
	struct parking_protocol_mailbox __iomem *mailbox;
	u32 cpu_id;

	/*
	 * Map mailbox memory with attribute device nGnRE (ie ioremap -
	 * this deviates from the parking protocol specifications since
	 * the mailboxes are required to be mapped nGnRnE; the attribute
	 * discrepancy is harmless insofar as the protocol specification
	 * is concerned).
	 * If the mailbox is mistakenly allocated in the linear mapping
	 * by FW ioremap will fail since the mapping will be prevented
	 * by the kernel (it clashes with the linear mapping attributes
	 * specifications).
	 */
	mailbox = ioremap(cpu_entry->mailbox_addr, sizeof(*mailbox));
	if (!mailbox)
		return -EIO;

	cpu_id = readl_relaxed(&mailbox->cpu_id);
	/*
	 * Check if firmware has set-up the mailbox entry properly
	 * before kickstarting the respective cpu.
	 */
	if (cpu_id != ~0U) {
		iounmap(mailbox);
		return -ENXIO;
	}

	/*
	 * stash the mailbox address mapping to use it for further FW
	 * checks in the postboot method
	 */
	cpu_entry->mailbox = mailbox;

	/*
	 * We write the entry point and cpu id as LE regardless of the
	 * native endianness of the kernel. Therefore, any boot-loaders
	 * that read this address need to convert this address to the
	 * Boot-Loader's endianness before jumping.
	 */
	writeq_relaxed(__pa_symbol(secondary_entry),
		       &mailbox->entry_point);
	writel_relaxed(cpu_entry->gic_cpu_id, &mailbox->cpu_id);

	arch_send_wakeup_ipi(cpu);

	return 0;
}

static void acpi_parking_protocol_cpu_postboot(void)
{
	int cpu = smp_processor_id();
	struct cpu_mailbox_entry *cpu_entry = &cpu_mailbox_entries[cpu];
	struct parking_protocol_mailbox __iomem *mailbox = cpu_entry->mailbox;
	u64 entry_point;

	entry_point = readq_relaxed(&mailbox->entry_point);
	/*
	 * Check if firmware has cleared the entry_point as expected
	 * by the protocol specification.
	 */
	WARN_ON(entry_point);
}

const struct cpu_operations acpi_parking_protocol_ops = {
	.name		= "parking-protocol",
	.cpu_init	= acpi_parking_protocol_cpu_init,
	.cpu_prepare	= acpi_parking_protocol_cpu_prepare,
	.cpu_boot	= acpi_parking_protocol_cpu_boot,
	.cpu_postboot	= acpi_parking_protocol_cpu_postboot
};