Messages in this thread Patch in this message | | | From | Christoph Hellwig <> | Subject | [PATCH 10/17] riscv: read the hart ID from mhartid on boot | Date | Mon, 24 Jun 2019 07:43:04 +0200 |
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From: Damien Le Moal <Damien.LeMoal@wdc.com>
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 <damien.lemoal@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> --- arch/riscv/kernel/head.S | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index e5fa5481aa99..a4c170e41a34 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -18,6 +18,14 @@ ENTRY(_start) csrw CSR_XIE, zero csrw CSR_XIP, zero +#ifdef CONFIG_M_MODE + /* + * The hartid in a0 is expected later on, and we have no firmware + * to hand it to us. + */ + csrr a0, mhartid +#endif + /* Load the global pointer */ .option push .option norelax -- 2.20.1
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