[14/17] arm: cpu: Add ACPI parking protocol support

On Arm platforms that use ACPI they cannot rely on the "spin-table"
CPU bringup usually defined in the FDT. Thus implement the
'ACPI Multi-processor Startup for ARM Platforms', also referred to as
'ACPI parking protocol'.

The ACPI parking protocol works similar to the spin-table mechanism, but
the specification also covers lots of shortcomings of the spin-table
implementations.

Every CPU defined in the ACPI MADT table has it's own 4K page where the
spinloop code and the OS mailbox resides. When selected the U-Boot board
code must make sure that the secondary CPUs enter u-boot after relocation
as well, so that they can enter the spinloop code residing in the ACPI
parking protocol pages.

The OS will then write to the mailbox and generate an IPI to release the
CPUs from the spinloop code.

For now it's only implemented on ARMv8, but can easily be extended to
other platforms.

TEST: Boots all CPUs on qemu-system-aarch64 -machine raspi4b

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
---
 arch/arm/cpu/armv8/Makefile              |   1 +
 arch/arm/cpu/armv8/parking_protocol_v8.S | 102 +++++++++++++++++++++++
 arch/arm/cpu/armv8/start.S               |   4 +
 arch/arm/include/asm/acpi_table.h        |  52 ++++++++++++
 arch/arm/lib/acpi_table.c                |  87 +++++++++++++++++++
 include/acpi/acpi_table.h                |  10 +++
 lib/Kconfig                              |  15 ++++
 lib/acpi/acpi_table.c                    |   3 +
 8 files changed, 274 insertions(+)
 create mode 100644 arch/arm/cpu/armv8/parking_protocol_v8.S

Hi Patrick,

On Sat, 27 Jul 2024 at 01:20, Patrick Rudolph
<patrick.rudolph@9elements.com> wrote:
>
> On Arm platforms that use ACPI they cannot rely on the "spin-table"
> CPU bringup usually defined in the FDT. Thus implement the
> 'ACPI Multi-processor Startup for ARM Platforms', also referred to as
> 'ACPI parking protocol'.
>
> The ACPI parking protocol works similar to the spin-table mechanism, but
> the specification also covers lots of shortcomings of the spin-table
> implementations.
>
> Every CPU defined in the ACPI MADT table has it's own 4K page where the
> spinloop code and the OS mailbox resides. When selected the U-Boot board
> code must make sure that the secondary CPUs enter u-boot after relocation

U-Boot

> as well, so that they can enter the spinloop code residing in the ACPI
> parking protocol pages.
>
> The OS will then write to the mailbox and generate an IPI to release the
> CPUs from the spinloop code.
>
> For now it's only implemented on ARMv8, but can easily be extended to
> other platforms.
>
> TEST: Boots all CPUs on qemu-system-aarch64 -machine raspi4b
>
> Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
> Cc: Simon Glass <sjg@chromium.org>
> Cc: Tom Rini <trini@konsulko.com>
> ---
>  arch/arm/cpu/armv8/Makefile              |   1 +
>  arch/arm/cpu/armv8/parking_protocol_v8.S | 102 +++++++++++++++++++++++
>  arch/arm/cpu/armv8/start.S               |   4 +
>  arch/arm/include/asm/acpi_table.h        |  52 ++++++++++++
>  arch/arm/lib/acpi_table.c                |  87 +++++++++++++++++++
>  include/acpi/acpi_table.h                |  10 +++
>  lib/Kconfig                              |  15 ++++
>  lib/acpi/acpi_table.c                    |   3 +
>  8 files changed, 274 insertions(+)
>  create mode 100644 arch/arm/cpu/armv8/parking_protocol_v8.S
>
> diff --git a/arch/arm/cpu/armv8/Makefile b/arch/arm/cpu/armv8/Makefile
> index bba4f570db..9bb07bdf12 100644
> --- a/arch/arm/cpu/armv8/Makefile
> +++ b/arch/arm/cpu/armv8/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_ARM_SMCCC)               += smccc-call.o
>
>  ifndef CONFIG_SPL_BUILD
>  obj-$(CONFIG_ARMV8_SPIN_TABLE) += spin_table.o spin_table_v8.o
> +obj-$(CONFIG_ACPI_PARKING_PROTOCOL) += parking_protocol_v8.o
>  else
>  obj-$(CONFIG_ARCH_SUNXI) += fel_utils.o
>  endif
> diff --git a/arch/arm/cpu/armv8/parking_protocol_v8.S b/arch/arm/cpu/armv8/parking_protocol_v8.S

How about acpi_park_v8.S as it is shorter?

> new file mode 100644
> index 0000000000..b7f6abbd85
> --- /dev/null
> +++ b/arch/arm/cpu/armv8/parking_protocol_v8.S
> @@ -0,0 +1,102 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Copyright (C) 2024 9elements GmbH
> + *   Author: Patrick Rudolph <patrick.rudolph@9elements.com>
> + */
> +
> +#include <linux/linkage.h>
> +#include <asm/acpi_table.h>
> +
> +__secondary_cpuif_id:
> +       .quad 0
> +
> +__secondary_parking_protocol_tables:
> +       .quad 0
> +
> +__secondary_parking_protocol_ncpus:
> +       .quad 0
> +
> +.global acpi_parking_protocol_code_size
> +acpi_parking_protocol_code_size:

acpi_park_code_size

acpi_parking_protocol is just too long

> +       .word __secondary_parking_protocol_code_end - __secondary_parking_protocol_code_start

Is there a 'primary'? Does this refer to the code run by the secondary CPUs?

> +
> +.global acpi_parking_protocol_install
> +ENTRY(acpi_parking_protocol_install)
> +       ldr     x2, =__secondary_parking_protocol_ncpus
> +       str     x1, [x2]
> +       ldr     x2, =__secondary_parking_protocol_tables
> +       str     x0, [x2]
> +       dsb     ishst
> +       sev
> +       ret
> +ENDPROC(acpi_parking_protocol_install)
> +
> +.global acpi_parking_protocol_secondary_jump
> +ENTRY(acpi_parking_protocol_secondary_jump)
> +0:
> +       /* Store a unique cpuif id in x0 */
> +       ldr     x2, =__secondary_cpuif_id
> +       ldaxr   w0, [x2]
> +       add     w0, w0, #1  // =1
> +       stlxr   w1, w0, [x2]
> +       cbnz    w1, 0b
> +
> +0:     /* Check if parking protocol table is ready */
> +       ldr     x1, =__secondary_parking_protocol_tables
> +       ldr     x2, [x1]
> +       cbnz    x2, 0f
> +       wfe
> +       b       0b
> +
> +0:     /* Sanity check cpuif id */
> +       ldr     x1, =__secondary_parking_protocol_ncpus
> +       ldr     x3, [x1]
> +       cmp     w0, w3
> +       b.lt    0f
> +
> +hlt:   wfi
> +       b       hlt     /* Should never happen. */
> +
> +       /* Find spinning code in ACPI parking protocol table */
> +0:     mov     x1, #ACPI_PP_PAGE_SIZE
> +       mul     x3, x0, x1
> +       add     x2, x2, x3
> +       mov     x0, x2          /* Backup ACPI page ptr for later use */
> +
> +       mov     x1, #ACPI_PP_CPU_CODE_OFFSET
> +       add     x2, x2, x1
> +
> +       /* Jump to spin code in own parking protocol page */
> +       br      x2
> +ENDPROC(acpi_parking_protocol_secondary_jump)
> +
> +.align 8
> +__secondary_parking_protocol_code_start:
> +.global acpi_parking_protocol_code_start
> +ENTRY(acpi_parking_protocol_code_start)
> +       /* x0 points to the 4K aligned parking protocol page */
> +
> +       /* Prepare defines for spinning code */
> +       mov     w3, #ACPI_PP_CPU_ID_INVALID
> +       mov     x2, #ACPI_PP_JMP_ADR_INVALID
> +
> +0:     wfe
> +       ldr     w1, [x0, #ACPI_PP_CPU_ID_OFFSET]
> +
> +       /* Check CPU ID is not invalid */
> +       cmp     w1, w3
> +       b.eq    0b
> +
> +       /* Check jump address not invalid */
> +       ldr     x1, [x0, #ACPI_PP_CPU_JMP_ADDR_OFFSET]
> +       cmp     x1, x2
> +       b.eq    0b
> +
> +       /* Clear jump address before jump */
> +       str     x2, [x0, #ACPI_PP_CPU_JMP_ADDR_OFFSET]
> +       dsb     sy
> +
> +       br      x1
> +ENDPROC(acpi_parking_protocol_code_start)
> +       /* Secondary Boot Code ends here */
> +__secondary_parking_protocol_code_end:
> diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
> index 7461280261..32a295c832 100644
> --- a/arch/arm/cpu/armv8/start.S
> +++ b/arch/arm/cpu/armv8/start.S
> @@ -178,6 +178,10 @@ pie_fixup_done:
>         branch_if_master x0, master_cpu
>         b       spin_table_secondary_jump
>         /* never return */
> +#elif defined(CONFIG_ACPI_PARKING_PROTOCOL) && !defined(CONFIG_SPL_BUILD)
> +       branch_if_master x0, master_cpu
> +       b       acpi_parking_protocol_secondary_jump
> +       /* never return */
>  #elif defined(CONFIG_ARMV8_MULTIENTRY)
>         branch_if_master x0, master_cpu
>
> diff --git a/arch/arm/include/asm/acpi_table.h b/arch/arm/include/asm/acpi_table.h
> index 8a25e93847..3c6736239d 100644
> --- a/arch/arm/include/asm/acpi_table.h
> +++ b/arch/arm/include/asm/acpi_table.h
> @@ -4,6 +4,7 @@
>  #define __ASM_ACPI_TABLE_H__
>
>  #ifndef __ACPI__
> +#ifndef __ASSEMBLY__
>
>  void acpi_write_madt_gicc(struct acpi_madt_gicc *gicc, uint cpu_num,
>                           uint perf_gsiv, ulong phys_base, ulong gicv,
> @@ -13,6 +14,57 @@ void acpi_write_madt_gicc(struct acpi_madt_gicc *gicc, uint cpu_num,
>  void acpi_write_madt_gicd(struct acpi_madt_gicd *gicd, uint gic_id,
>                           ulong phys_base, uint gic_version);
>
> +/* Multi-processor Startup for ARM Platforms */

please add full comments for members

> +struct acpi_parking_protocol_page {
> +       u32 cpu_id;
> +       u32 reserved;
> +       u64 jumping_address;
> +       u8 os_reserved[2032];
> +       u8 cpu_spinning_code[2048];
> +} __packed;
> +
> +/* Architecture specific functions */
> +/**
> + * acpi_parking_protocol_code_size - Spinloop code size *
> + */
> +extern u32 acpi_parking_protocol_code_size;

u32 but it says .word in the code...isn't that 16 bits?

> +
> +/**
> + * parking_protocol_code_start() - Spinloop code
> + *
> + * Architectural spinloop code to be installed in each parking protocol
> + * page. The spinloop code must be less than 2048 bytes.
> + *
> + * The spinloop code will be entered after calling
> + * acpi_parking_protocol_install().
> + *
> + */
> +void acpi_parking_protocol_code_start(void);
> +
> +/**
> + * acpi_parking_protocol_install() - Installs the parking protocol.
> + *
> + * Installs the reserved memory containing the spinloop code and the
> + * OS mailbox as required by the ACPI Multi-processor Startup for
> + * ARM Platforms specification.
> + *
> + * The secondary CPUs will wait for this function to be called in order
> + * to enter the spinloop code residing in the tables.
> + *
> + * @tables: ACPI parking protocol tables.
> + * @num_cpus: Number of allocated pages.
> + */
> +void acpi_parking_protocol_install(uintptr_t tables, size_t num_cpus);
> +
> +#endif /* !__ASSEMBLY__ */
>  #endif /* !__ACPI__ */
>
> +#define ACPI_PP_CPU_ID_INVALID         0xffffffff
> +#define ACPI_PP_JMP_ADR_INVALID                0
> +#define ACPI_PP_PAGE_SIZE              4096
> +#define ACPI_PP_CPU_ID_OFFSET          0
> +#define ACPI_PP_CPU_JMP_ADDR_OFFSET    8
> +#define ACPI_PP_CPU_CODE_OFFSET                2048
> +#define ACPI_PP_VERSION                        1
> +
>  #endif /* __ASM_ACPI_TABLE_H__ */
> diff --git a/arch/arm/lib/acpi_table.c b/arch/arm/lib/acpi_table.c
> index ea3a6343c9..2fa25ec50e 100644
> --- a/arch/arm/lib/acpi_table.c
> +++ b/arch/arm/lib/acpi_table.c
> @@ -10,7 +10,11 @@
>  #include <acpi/acpigen.h>
>  #include <acpi/acpi_device.h>
>  #include <acpi/acpi_table.h>
> +#include <cpu_func.h>
> +#include <efi_loader.h>
> +#include <malloc.h>
>  #include <string.h>
> +#include <tables_csum.h>
>
>  void acpi_write_madt_gicc(struct acpi_madt_gicc *gicc, uint cpu_num,
>                           uint perf_gsiv, ulong phys_base, ulong gicv,
> @@ -42,3 +46,86 @@ void acpi_write_madt_gicd(struct acpi_madt_gicd *gicd, uint gic_id,
>         gicd->phys_base = phys_base;
>         gicd->gic_version = gic_version;
>  }
> +
> +void acpi_write_parking_protocol(struct acpi_madt *madt)
> +{
> +       struct acpi_parking_protocol_page *page;
> +       struct acpi_madt_gicc *gicc;
> +       void *reloc_addr;
> +       u64 start;
> +       int ncpus = 0;
> +
> +       /* According to the "Multi-processor Startup for ARM Platforms":
> +        * - Every CPU as specified by MADT GICC has it's own 4K page
> +        * - Every page is divided into two sections: OS and FW reserved
> +        * - Memory occupied by "Parking Protocol" must be marked 'Reserved'
> +        * - Spinloop code should reside in FW reserved 2048 bytes
> +        * - Spinloop code will check the mailbox in OS reserved area
> +        */
> +
> +       if (acpi_parking_protocol_code_size > sizeof(page->cpu_spinning_code)) {
> +               log_err("Spinning code too big to fit: %d\n",
> +                       acpi_parking_protocol_code_size);
> +       }
> +
> +       /* Count all cores including BSP */

Ick, that's a very strange way of counting CPUs. You can use
uclass_id_count(UCLASS_CPU).

> +       for (int i = sizeof(struct acpi_madt); i < madt->header.length; ) {
> +               gicc = (struct acpi_madt_gicc *)((void *)madt + i);
> +               if (gicc->type != ACPI_APIC_GICC) {
> +                       i += gicc->length;
> +                       continue;
> +               }
> +               ncpus++;
> +               i += gicc->length;
> +       }
> +       debug("Found %d GICCs in MADT\n", ncpus);
> +
> +       /* Allocate pages linearly due to assembly code requirements */
> +       page = memalign(ACPI_PP_PAGE_SIZE, ACPI_PP_PAGE_SIZE * ncpus);
> +       start = (u64)(uintptr_t)page;

Again, this should go in the bloblist.

> +
> +#if CONFIG_IS_ENABLED(EFI_LOADER)
> +       int ret = efi_add_memory_map(start, ncpus * ACPI_PP_PAGE_SIZE, EFI_RESERVED_MEMORY_TYPE);
> +
> +       if (ret != EFI_SUCCESS)
> +               log_err("Reserved memory mapping failed addr %llx size %x\n",
> +                       start, ncpus * ACPI_PP_PAGE_SIZE);
> +#endif

This map will overlap the one that EFI creates for the malloc()
region, won't it?

> +
> +       /* Prepare the parking protocol pages */
> +       for (int i = sizeof(struct acpi_madt); i < madt->header.length; ) {

please use 'pos' instead of 'i' as this isn't really an index

> +               gicc = (struct acpi_madt_gicc *)((void *)madt + i);

Can you put the loop code in a separate function? This is getting a
bit long for one function

> +               if (gicc->type != ACPI_APIC_GICC) {
> +                       i += gicc->length;
> +                       continue;
> +               }
> +
> +               /* Update GICC */
> +               gicc->parking_proto = ACPI_PP_VERSION;
> +               gicc->parked_addr = (uint64_t)(uintptr_t)page;
> +
> +               /* Prepare parking protocol page */
> +               memset(page, 0, sizeof(struct acpi_parking_protocol_page));

'\0'

> +               page->cpu_id = ACPI_PP_CPU_ID_INVALID;
> +               page->jumping_address = ACPI_PP_JMP_ADR_INVALID;
> +
> +               /* Relocate spinning code */
> +               reloc_addr = &page->cpu_spinning_code[0];
> +
> +               debug("Relocating spin table from %p to %p (size %x)\n",
> +                     &acpi_parking_protocol_code_start, reloc_addr,
> +                     acpi_parking_protocol_code_size);
> +               memcpy(reloc_addr, &acpi_parking_protocol_code_start,
> +                      acpi_parking_protocol_code_size);
> +
> +               if (!CONFIG_IS_ENABLED(SYS_DCACHE_OFF))
> +                       flush_dcache_range((unsigned long)page,
> +                                          (unsigned long)page +
> +                                          sizeof(struct acpi_parking_protocol_page));
> +               page++;
> +               i += gicc->length;
> +       }
> +
> +       /* Point secondary CPUs to new spin loop code */
> +       acpi_parking_protocol_install(start, ncpus);
> +}
> diff --git a/include/acpi/acpi_table.h b/include/acpi/acpi_table.h
> index 26c5e9f21a..994bfd7f8d 100644
> --- a/include/acpi/acpi_table.h
> +++ b/include/acpi/acpi_table.h
> @@ -951,6 +951,16 @@ void acpi_fill_fadt(struct acpi_fadt *fadt);
>   */
>  void *acpi_fill_madt(struct acpi_madt *madt, void *current);
>
> +/**
> + * acpi_write_parking_protocol() - Installs the ACPI parking protocol.
> + *
> + * Sets up the ACPI parking protocol and installs the spinning code for
> + * secondary CPUs.
> + *
> + * @madt: The MADT to update
> + */
> +void acpi_write_parking_protocol(struct acpi_madt *madt);
> +
>  /**
>   * acpi_write_dbg2_pci_uart() - Write out a DBG2 table
>   *
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 2059219a12..43e4fa3253 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -314,6 +314,21 @@ config GENERATE_ACPI_TABLE
>           by the operating system. It defines platform-independent interfaces
>           for configuration and power management monitoring.
>
> +config ACPI_PARKING_PROTOCOL
> +       bool "Support ACPI parking protocol method"
> +       depends on GENERATE_ACPI_TABLE
> +       depends on ARMV8_MULTIENTRY
> +       default y if !SEC_FIRMWARE_ARMV8_PSCI && !ARMV8_PSCI
> +       help
> +         Say Y here to support "ACPI parking protocol" enable method
> +         for booting Linux.
> +
> +         To use this feature, you must do:
> +           - Bring secondary CPUs into U-Boot proper in a board specific
> +             manner.  This must be done *after* relocation.  Otherwise, the
> +             secondary CPUs will spin in unprotected memory area because the
> +             master CPU protects the relocated spin code.
> +
>  config SPL_TINY_MEMSET
>         bool "Use a very small memset() in SPL"
>         depends on SPL
> diff --git a/lib/acpi/acpi_table.c b/lib/acpi/acpi_table.c
> index eb3c83ab02..56eb4a10d0 100644
> --- a/lib/acpi/acpi_table.c
> +++ b/lib/acpi/acpi_table.c
> @@ -271,6 +271,9 @@ int acpi_write_madt(struct acpi_ctx *ctx, const struct acpi_writer *entry)
>         /* (Re)calculate length and checksum */
>         header->length = (uintptr_t)current - (uintptr_t)madt;
>
> +       if (IS_ENABLED(CONFIG_ACPI_PARKING_PROTOCOL))
> +               acpi_write_parking_protocol(madt);
> +
>         header->checksum = table_compute_checksum((void *)madt, header->length);
>         acpi_add_table(ctx, madt);
>         acpi_inc(ctx, madt->header.length);
> --
> 2.45.2
>

Regards,
Simon