-----Original Message----- From: Lukas Auer [mailto:lukas.auer@aisec.fraunhofer.de] Sent: Tuesday, February 12, 2019 3:44 AM To: u-boot@lists.denx.de Cc: Atish Patra Atish.Patra@wdc.com; Anup Patel Anup.Patel@wdc.com; Bin Meng bmeng.cn@gmail.com; Andreas Schwab schwab@suse.de; Palmer Dabbelt palmer@sifive.com; Alexander Graf agraf@suse.de; Lukas Auer lukas.auer@aisec.fraunhofer.de; Anup Patel anup@brainfault.org; Rick Chen rick@andestech.com; Baruch Siach baruch@tkos.co.il; Stefan Roese sr@denx.de Subject: [PATCH 5/7] riscv: add support for multi-hart systems
On RISC-V, all harts boot independently. To be able to run on a multi-hart system, U-Boot must be extended with the functionality to manage all harts in the system. A new config option, CONFIG_MAIN_HART, is used to select the hart U-Boot runs on. All other harts are halted. U-Boot can delegate functions to them using smp_call_function().
Every hart has a valid pointer to the global data structure and a 8KiB stack by default. The stack size is set with CONFIG_STACK_SIZE_SHIFT.
Signed-off-by: Lukas Auer lukas.auer@aisec.fraunhofer.de
arch/riscv/Kconfig | 12 +++++ arch/riscv/cpu/start.S | 102 ++++++++++++++++++++++++++++++++++- arch/riscv/include/asm/csr.h | 1 + 3 files changed, 114 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 3a51339c4d..af8d0f8d67 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -140,4 +140,16 @@ config SBI_IPI default y if RISCV_SMODE depends on SMP
+config MAIN_HART
- int "Main hart in system"
- default 0
- help
Some SoCs include harts of various sizes, some of which might notbe suitable for running U-Boot. CONFIG_MAIN_HART is used toselect
the hart U-Boot runs on.
This config option can be avoided altogether if we have lottery based system to select "Main HART" in start.S.
With the MAIN_HART config option in-place, every system will have to pick a "Main HART". What if the "Main HART" itself does not come online due to HW failure.
Regards, Anup