[U-Boot] [PATCH 1/7] riscv: add infrastructure for calling functions on other harts
Auer, Lukas
lukas.auer at aisec.fraunhofer.de
Sun Feb 17 21:55:14 UTC 2019
On Tue, 2019-02-12 at 01:44 +0000, Anup Patel wrote:
> > -----Original Message-----
> > From: Lukas Auer [mailto:lukas.auer at aisec.fraunhofer.de]
> > Sent: Tuesday, February 12, 2019 3:44 AM
> > To: u-boot at lists.denx.de
> > Cc: Atish Patra <Atish.Patra at wdc.com>; Anup Patel
> > <Anup.Patel at wdc.com>; Bin Meng <bmeng.cn at gmail.com>; Andreas
> > Schwab <schwab at suse.de>; Palmer Dabbelt <palmer at sifive.com>;
> > Alexander Graf <agraf at suse.de>; Lukas Auer
> > <lukas.auer at aisec.fraunhofer.de>; Anup Patel <anup at brainfault.org>;
> > Rick
> > Chen <rick at andestech.com>
> > Subject: [PATCH 1/7] riscv: add infrastructure for calling
> > functions on other
> > harts
> >
> > Harts on RISC-V boot independently and 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 harts.
> > 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 at aisec.fraunhofer.de>
> > ---
> >
> > arch/riscv/Kconfig | 19 +++++
> > arch/riscv/include/asm/global_data.h | 5 ++
> > arch/riscv/include/asm/smp.h | 53 +++++++++++++
> > arch/riscv/lib/Makefile | 1 +
> > arch/riscv/lib/smp.c | 110
> > +++++++++++++++++++++++++++
> > 5 files changed, 188 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
> > c45e4d73a8..c0842178dd 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -116,4 +116,23 @@ 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..23a5f35af5 100644
> > --- a/arch/riscv/include/asm/global_data.h
> > +++ b/arch/riscv/include/asm/global_data.h
> > @@ -10,12 +10,17 @@
> > #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
> > };
> >
> > #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 at 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..1266a2a0ef
> > --- /dev/null
> > +++ b/arch/riscv/lib/smp.c
> > @@ -0,0 +1,110 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2019 Fraunhofer AISEC,
> > + * Lukas Auer <lukas.auer at 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) {
> > + if (!ofnode_is_available(node))
> > + continue;
>
> It is not correct to assume that whatever CPUs are marked
> available will come online. It is possible that certain available
> CPUs failed to come online due HW failure.
>
This was intended so that we don't send IPIs to harts, which have been
explicitly marked as disabled.
> Better approach would be keep an atomic bitmask of HARTs
> that have entered U-Boot. All HARTs that enter U-Boot will
> update the atomic HART available bitmask. We send IPI only
> to HARTs that are available as-per atomic HART bitmask.
>
I'm not sure if this is required in U-Boot, since we are not relying on
all harts to boot for U-Boot to function. We only try to boot all harts
listed as available in the device tree.
Is there a situation, in which we would want to avoid sending an IPI to
an unavailable hart?
Thanks,
Lukas
> > +
> > + /* 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;
> > + }
> > +
> > + gd->arch.ipi[reg].addr = ipi->addr;
> > + gd->arch.ipi[reg].arg0 = ipi->arg0;
> > + gd->arch.ipi[reg].arg1 = ipi->arg1;
> > + mb();
> > +
> > + ret = riscv_send_ipi(reg);
> > + if (ret)
> > + 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\n");
> > + return;
> > + }
> > +
> > + 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;
> > +}
> > --
> > 2.20.1
>
> Regards,
> Anup
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