linux/arch/arm64/kernel/acpi_parking_protocol.c
Mark Rutland 2b2d0a7a96 arm64: smp: Remove dedicated wakeup IPI
To enable NMI backtrace and KGDB's NMI cpu roundup, we need to free up
at least one dedicated IPI.

On arm64 the IPI_WAKEUP IPI is only used for the ACPI parking protocol,
which itself is only used on some very early ARMv8 systems which
couldn't implement PSCI.

Remove the IPI_WAKEUP IPI, and rely on the IPI_RESCHEDULE IPI to wake
CPUs from the parked state. This will cause a tiny amonut of redundant
work to check the thread flags, but this is miniscule in relation to the
cost of taking and handling the IPI in the first place. We can safely
handle redundant IPI_RESCHEDULE IPIs, so there should be no functional
impact as a result of this change.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230906090246.v13.3.I7209db47ef8ec151d3de61f59005bbc59fe8f113@changeid
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2023-09-25 17:15:28 +01:00

133 lines
3.5 KiB
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
};