Harts on RISC-V boot independently, U-Boot is responsible for managing them. Functions are called on other harts with smp_call_function(), which sends inter-processor interrupts (IPIs) to all other available harts. Available harts are those marked as available in the device tree and present in the available_harts mask stored in global data. The available_harts mask is used to register all harts that have entered U-Boot. Functions are specified with their address and two function arguments (argument 2 and 3). The first function argument is always the hart ID of the hart calling the function. On the other harts, the IPI interrupt handler handle_ipi() must be called on software interrupts to handle the request and call the specified function.
Functions are stored in the ipi_data data structure. Every hart has its own data structure in global data. While this is not required at the moment (all harts are expected to boot Linux), this does allow future expansion, where other harts may be used for monitoring or other tasks.
Signed-off-by: Lukas Auer lukas.auer@aisec.fraunhofer.de Reviewed-by: Anup Patel anup.patel@wdc.com Reviewed-by: Bin Meng bmeng.cn@gmail.com Tested-by: Bin Meng bmeng.cn@gmail.com ---
Changes in v3: - Print error if riscv_send_ipi() fails - Adjust error message for failures of riscv_clear_ipi() to match error message for failures of riscv_send_ipi()
Changes in v2: - Remove unneeded quotes from NR_CPUS Kconfig entry - Move memory barrier from send_ipi_many() to handle_ipi() - Add check in send_ipi_many so that IPIs are only sent to available harts as indicated by the available_harts mask
arch/riscv/Kconfig | 19 +++++ arch/riscv/include/asm/global_data.h | 6 ++ arch/riscv/include/asm/smp.h | 53 ++++++++++++ arch/riscv/lib/Makefile | 1 + arch/riscv/lib/smp.c | 118 +++++++++++++++++++++++++++ 5 files changed, 197 insertions(+) create mode 100644 arch/riscv/include/asm/smp.h create mode 100644 arch/riscv/lib/smp.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 36512a8995..4d7a115569 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -120,4 +120,23 @@ config RISCV_RDTIME config SYS_MALLOC_F_LEN default 0x1000
+config SMP + bool "Symmetric Multi-Processing" + help + This enables support for systems with more than one CPU. If + you say N here, U-Boot will run on single and multiprocessor + machines, but will use only one CPU of a multiprocessor + machine. If you say Y here, U-Boot will run on many, but not + all, single processor machines. + +config NR_CPUS + int "Maximum number of CPUs (2-32)" + range 2 32 + depends on SMP + default 8 + help + On multiprocessor machines, U-Boot sets up a stack for each CPU. + Stack memory is pre-allocated. U-Boot must therefore know the + maximum number of CPUs that may be present. + endmenu diff --git a/arch/riscv/include/asm/global_data.h b/arch/riscv/include/asm/global_data.h index a3a342c6e1..80e3165e39 100644 --- a/arch/riscv/include/asm/global_data.h +++ b/arch/riscv/include/asm/global_data.h @@ -10,12 +10,18 @@ #ifndef __ASM_GBL_DATA_H #define __ASM_GBL_DATA_H
+#include <asm/smp.h> + /* Architecture-specific global data */ struct arch_global_data { long boot_hart; /* boot hart id */ #ifdef CONFIG_SIFIVE_CLINT void __iomem *clint; /* clint base address */ #endif +#ifdef CONFIG_SMP + struct ipi_data ipi[CONFIG_NR_CPUS]; +#endif + ulong available_harts; };
#include <asm-generic/global_data.h> diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h new file mode 100644 index 0000000000..bc863fdbaf --- /dev/null +++ b/arch/riscv/include/asm/smp.h @@ -0,0 +1,53 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2019 Fraunhofer AISEC, + * Lukas Auer lukas.auer@aisec.fraunhofer.de + */ + +#ifndef _ASM_RISCV_SMP_H +#define _ASM_RISCV_SMP_H + +/** + * struct ipi_data - Inter-processor interrupt (IPI) data structure + * + * IPIs are used for SMP support to communicate to other harts what function to + * call. Functions are in the form + * void (*addr)(ulong hart, ulong arg0, ulong arg1). + * + * The function address and the two arguments, arg0 and arg1, are stored in the + * IPI data structure. The hart ID is inserted by the hart handling the IPI and + * calling the function. + * + * @addr: Address of function + * @arg0: First argument of function + * @arg1: Second argument of function + */ +struct ipi_data { + ulong addr; + ulong arg0; + ulong arg1; +}; + +/** + * handle_ipi() - interrupt handler for software interrupts + * + * The IPI interrupt handler must be called to handle software interrupts. It + * calls the function specified in the hart's IPI data structure. + * + * @hart: Hart ID of the current hart + */ +void handle_ipi(ulong hart); + +/** + * smp_call_function() - Call a function on all other harts + * + * Send IPIs with the specified function call to all harts. + * + * @addr: Address of function + * @arg0: First argument of function + * @arg1: Second argument of function + * @return 0 if OK, -ve on error + */ +int smp_call_function(ulong addr, ulong arg0, ulong arg1); + +#endif diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index edfa61690c..19370f9749 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -14,6 +14,7 @@ obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint.o obj-y += interrupts.o obj-y += reset.o obj-y += setjmp.o +obj-$(CONFIG_SMP) += smp.o
# For building EFI apps CFLAGS_$(EFI_CRT0) := $(CFLAGS_EFI) diff --git a/arch/riscv/lib/smp.c b/arch/riscv/lib/smp.c new file mode 100644 index 0000000000..caa292ccd2 --- /dev/null +++ b/arch/riscv/lib/smp.c @@ -0,0 +1,118 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2019 Fraunhofer AISEC, + * Lukas Auer lukas.auer@aisec.fraunhofer.de + */ + +#include <common.h> +#include <dm.h> +#include <asm/barrier.h> +#include <asm/smp.h> + +DECLARE_GLOBAL_DATA_PTR; + +/** + * riscv_send_ipi() - Send inter-processor interrupt (IPI) + * + * Platform code must provide this function. + * + * @hart: Hart ID of receiving hart + * @return 0 if OK, -ve on error + */ +extern int riscv_send_ipi(int hart); + +/** + * riscv_clear_ipi() - Clear inter-processor interrupt (IPI) + * + * Platform code must provide this function. + * + * @hart: Hart ID of hart to be cleared + * @return 0 if OK, -ve on error + */ +extern int riscv_clear_ipi(int hart); + +static int send_ipi_many(struct ipi_data *ipi) +{ + ofnode node, cpus; + u32 reg; + int ret; + + cpus = ofnode_path("/cpus"); + if (!ofnode_valid(cpus)) { + pr_err("Can't find cpus node!\n"); + return -EINVAL; + } + + ofnode_for_each_subnode(node, cpus) { + /* skip if hart is marked as not available in the device tree */ + if (!ofnode_is_available(node)) + continue; + + /* read hart ID of CPU */ + ret = ofnode_read_u32(node, "reg", ®); + if (ret) + continue; + + /* skip if it is the hart we are running on */ + if (reg == gd->arch.boot_hart) + continue; + + if (reg >= CONFIG_NR_CPUS) { + pr_err("Hart ID %d is out of range, increase CONFIG_NR_CPUS\n", + reg); + continue; + } + + /* skip if hart is not available */ + if (!(gd->arch.available_harts & (1 << reg))) + continue; + + gd->arch.ipi[reg].addr = ipi->addr; + gd->arch.ipi[reg].arg0 = ipi->arg0; + gd->arch.ipi[reg].arg1 = ipi->arg1; + + ret = riscv_send_ipi(reg); + if (ret) { + pr_err("Cannot send IPI to hart %d\n", reg); + return ret; + } + } + + return 0; +} + +void handle_ipi(ulong hart) +{ + int ret; + void (*smp_function)(ulong hart, ulong arg0, ulong arg1); + + if (hart >= CONFIG_NR_CPUS) + return; + + ret = riscv_clear_ipi(hart); + if (ret) { + pr_err("Cannot clear IPI of hart %ld\n", hart); + return; + } + + __smp_mb(); + + smp_function = (void (*)(ulong, ulong, ulong))gd->arch.ipi[hart].addr; + invalidate_icache_all(); + + smp_function(hart, gd->arch.ipi[hart].arg0, gd->arch.ipi[hart].arg1); +} + +int smp_call_function(ulong addr, ulong arg0, ulong arg1) +{ + int ret = 0; + struct ipi_data ipi; + + ipi.addr = addr; + ipi.arg0 = arg0; + ipi.arg1 = arg1; + + ret = send_ipi_many(&ipi); + + return ret; +}