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SubjectRe: [PATCH 10/17] riscv: read the hart ID from mhartid on boot
Date
On Mon, 2019-06-24 at 07:43 +0200, Christoph Hellwig wrote:
> 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

I think you should add SR_MHARTID and use that instead of direct csr
name.
The following patch replaced all occurrence of csr name usage from
kernel with CSR numbers.

https://patchwork.kernel.org/patch/10916293/

With that change,

Reviewed-by: Atish Patra <atish.patra@wdc.com>

> +#endif
> +
> /* Load the global pointer */
> .option push
> .option norelax

--
Regards,
Atish
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