Commit accb9dbc authored by Damien Le Moal's avatar Damien Le Moal Committed by Paul Walmsley
Browse files

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: default avatarDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: default avatarAnup Patel <anup@brainfault.org>
Reviewed-by: default avatarAtish Patra <atish.patra@wdc.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarPaul Walmsley <paul.walmsley@sifive.com>
parent fcdc6537

arch/riscv/include/asm/csr.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/riscv/kernel/head.S

+8 −0
Original line number Diff line number Diff line
@@ -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

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