From accb9dbc4affdb7ebf30db7e9ba71eee47280081 Mon Sep 17 00:00:00 2001 From: Damien Le Moal Date: Mon, 28 Oct 2019 13:10:39 +0100 Subject: [PATCH] riscv: read the hart ID from mhartid on boot When in M-Mode, we can use the mhartid CSR to get the ID of the running HART. Doing so, direct M-Mode boot without firmware is possible. Signed-off-by: Damien Le Moal Reviewed-by: Anup Patel Reviewed-by: Atish Patra Signed-off-by: Christoph Hellwig Signed-off-by: Paul Walmsley --- arch/riscv/include/asm/csr.h | 1 + arch/riscv/kernel/head.S | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h index 0ab6428..318192c 100644 --- a/arch/riscv/include/asm/csr.h +++ b/arch/riscv/include/asm/csr.h @@ -99,6 +99,7 @@ #define CSR_MCAUSE 0x342 #define CSR_MTVAL 0x343 #define CSR_MIP 0x344 +#define CSR_MHARTID 0xf14 #ifdef CONFIG_RISCV_M_MODE # define CSR_STATUS CSR_MSTATUS diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index 5cfd2c5..fc99730 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -50,6 +50,14 @@ _start_kernel: csrw CSR_IE, zero csrw CSR_IP, zero +#ifdef CONFIG_RISCV_M_MODE + /* + * The hartid in a0 is expected later on, and we have no firmware + * to hand it to us. + */ + csrr a0, CSR_MHARTID +#endif + /* Load the global pointer */ .option push .option norelax -- 2.7.4