From 34bfe8eff895b864247d923ce37110a9053592ee Mon Sep 17 00:00:00 2001 From: Patrick Rudolph Date: Wed, 23 Oct 2024 15:20:13 +0200 Subject: 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, like ARMv7. TEST: Boots all CPUs on qemu-system-aarch64 -machine raspi4b Signed-off-by: Patrick Rudolph Reviewed-by: Simon Glass Cc: Simon Glass Cc: Tom Rini --- arch/arm/cpu/armv8/Makefile | 1 + arch/arm/cpu/armv8/acpi_park_v8.S | 113 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 114 insertions(+) create mode 100644 arch/arm/cpu/armv8/acpi_park_v8.S (limited to 'arch/arm/cpu') diff --git a/arch/arm/cpu/armv8/Makefile b/arch/arm/cpu/armv8/Makefile index bba4f570dbb..4f4368ff8c7 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-$(CONFIG_ACPI_PARKING_PROTOCOL) += acpi_park_v8.o else obj-$(CONFIG_ARCH_SUNXI) += fel_utils.o endif diff --git a/arch/arm/cpu/armv8/acpi_park_v8.S b/arch/arm/cpu/armv8/acpi_park_v8.S new file mode 100644 index 00000000000..0bc605d28df --- /dev/null +++ b/arch/arm/cpu/armv8/acpi_park_v8.S @@ -0,0 +1,113 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (C) 2024 9elements GmbH + * Author: Patrick Rudolph + * + * This file provides ARMv8 specific code for the generic part of the + * ACPI parking protocol implementation. It contains the spinning code + * that will be installed into the parking protocol and it points the + * secondary CPUs to their own parking protocol page once it has been + * set up by the generic part. + */ + +#include +#include + +/* Filled by C code */ +.global acpi_pp_tables +acpi_pp_tables: + .quad 0 + +.global acpi_pp_etables +acpi_pp_etables: + .quad 0 + +/* Read by C code */ +.global acpi_pp_code_size +acpi_pp_code_size: + .word __secondary_pp_code_end - __secondary_pp_code_start + +.global acpi_pp_secondary_jump +ENTRY(acpi_pp_secondary_jump) +0: + /* + * Cannot use atomic operations since the MMU and D-cache + * might be off. Use the MPIDR instead to find the spintable. + */ + + /* Check if parking protocol table is ready */ + ldr x1, =acpi_pp_tables + ldr x0, [x1] + cbnz x0, 0f + wfe + b 0b + +0: /* Get end of page tables in x3 */ + ldr x1, =acpi_pp_etables + ldr x3, [x1] + + /* Get own CPU ID in w2 */ + mrs x2, mpidr_el1 + lsr x9, x2, #32 + bfi x2, x9, #24, #8 /* w2 is aff3:aff2:aff1:aff0 */ + +0: /* Loop over all parking protocol pages */ + cmp x0, x3 + b.ge hlt + + /* Fetch CPU_ID from current page */ + ldr x1, [x0, #ACPI_PP_CPU_ID_OFFSET] + lsr x9, x1, #32 + bfi x1, x9, #24, #8 /* w1 is aff3:aff2:aff1:aff0 */ + + /* Compare CPU_IDs */ + cmp w1, w2 + b.eq 0f + + add x0, x0, #ACPI_PP_PAGE_SIZE + b 0b + +hlt: wfi + b hlt /* Should never happen. */ + +0: /* x0 points to the 4K-aligned, parking protocol page */ + add x2, x0, #ACPI_PP_CPU_CODE_OFFSET + + /* Jump to spin code in own parking protocol page */ + br x2 +ENDPROC(acpi_pp_secondary_jump) + +.align 8 +__secondary_pp_code_start: +.global acpi_pp_code_start +ENTRY(acpi_pp_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 + + /* Mark parking protocol page as ready */ + str w3, [x0, #ACPI_PP_CPU_ID_OFFSET] + dsb sy + +0: wfe + ldr w1, [x0, #ACPI_PP_CPU_ID_OFFSET] + + /* Check CPU ID is valid */ + cmp w1, w3 + b.eq 0b + + /* Check jump address valid */ + ldr x1, [x0, #ACPI_PP_CPU_JMP_OFFSET] + cmp x1, x2 + b.eq 0b + + /* Clear jump address before jump */ + str x2, [x0, #ACPI_PP_CPU_JMP_OFFSET] + dsb sy + + br x1 +ENDPROC(acpi_pp_code_start) + /* Secondary Boot Code ends here */ +__secondary_pp_code_end: -- cgit v1.3.1 From 92e02b01eceacb21c65c1aa07e3ca0695fdbaff7 Mon Sep 17 00:00:00 2001 From: Patrick Rudolph Date: Wed, 23 Oct 2024 15:20:14 +0200 Subject: armv8: cpu: Enable ACPI parking protocol Update the generic entry point code to support the ACPI parking protocol. The ACPI parking protocol can be used when PSCI is not available to bring up secondary CPU cores. When enabled secondary CPUs will enter U-Boot proper and spin in their own 4KiB reserved memory page, which also acts as mailbox with the OS to release the CPU. TEST: Boots all CPUs on qemu-system-aarch64 -machine raspi4b Signed-off-by: Patrick Rudolph Reviewed-by: Simon Glass --- arch/arm/cpu/armv8/start.S | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'arch/arm/cpu') diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S index 74612802617..544a4a53645 100644 --- a/arch/arm/cpu/armv8/start.S +++ b/arch/arm/cpu/armv8/start.S @@ -178,6 +178,18 @@ 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 + /* + * Waits for ACPI parking protocol memory to be allocated and the spin-table + * code to be written. Once ready the secondary CPUs will jump and spin in + * their own 4KiB memory region, which is also used as mailbox, until released + * by the OS. + * The mechanism is similar to the DT enable-method = "spin-table", but works + * with ACPI enabled platforms. + */ + b acpi_pp_secondary_jump + /* never return */ #elif defined(CONFIG_ARMV8_MULTIENTRY) branch_if_master x0, master_cpu -- cgit v1.3.1