[PATCH 01/11] lib: sbi: Fix sbi_hart_switch_mode() for u-mode

[Alistair Francis]

On Sat, 2020-11-21 at 15:17 +0530, Anup Patel wrote:
> We should check and access N-extension CSRs in sbi_hart_switch_mode()
> when next_mode is u-mode because N-extension is optional.
> 
> Signed-off-by: Anup Patel <anup.patel at wdc.com>

Reviewed-by: Alistair Francis <alistair.francis at wdc.com>

Alistair

> ---
>  lib/sbi/sbi_hart.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 30d8aef..fc86e9f 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -522,9 +522,11 @@ sbi_hart_switch_mode(unsigned long arg0,
> unsigned long arg1,
>                 csr_write(CSR_SIE, 0);
>                 csr_write(CSR_SATP, 0);
>         } else if (next_mode == PRV_U) {
> -               csr_write(CSR_UTVEC, next_addr);
> -               csr_write(CSR_USCRATCH, 0);
> -               csr_write(CSR_UIE, 0);
> +               if (misa_extension('N')) {
> +                       csr_write(CSR_UTVEC, next_addr);
> +                       csr_write(CSR_USCRATCH, 0);
> +                       csr_write(CSR_UIE, 0);
> +               }
>         }
>  
>         register unsigned long a0 asm("a0") = arg0;