[RFC PATCH v4 2/2] board: sifive: unmatched: clear feature disable CSR

[Bin Meng]

On Tue, Mar 30, 2021 at 1:27 PM Green Wan <green.wan at sifive.com> wrote:
>
> Clear feature disable CSR to turn on all features of hart. The detail
> is specified at section, 'SiFive Feature Disable CSR', in user manual
>
> https://sifive.cdn.prismic.io/sifive/aee0dd4c-d156-496e-a6c4-db0cf54bbe68_sifive_U74MC_rtl_full_20G1.03.00_manual.pdf
>
> Signed-off-by: Green Wan <green.wan at sifive.com>
> Reviewed-by: Sean Anderson <seanga2 at gmail.com>
> ---
>  board/sifive/unmatched/spl.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/board/sifive/unmatched/spl.c b/board/sifive/unmatched/spl.c
> index 5e1333b09a..2af3069b55 100644
> --- a/board/sifive/unmatched/spl.c
> +++ b/board/sifive/unmatched/spl.c
> @@ -12,6 +12,7 @@
>  #include <log.h>
>  #include <linux/delay.h>
>  #include <linux/io.h>
> +#include <asm/csr.h>
>  #include <asm/gpio.h>
>  #include <asm/arch/gpio.h>
>  #include <asm/arch/spl.h>
> @@ -22,6 +23,20 @@
>  #define MODE_SELECT_SD         0xb
>  #define MODE_SELECT_MASK       GENMASK(3, 0)
>
> +#define CSR_U74_FEATURE_DISABLE        0x7c1
> +
> +void riscv_hart_early_init(void)
> +{
> +       /*
> +        * Feature Disable CSR
> +        *
> +        * Clear feature disable CSR to '0' to turn on all features for
> +        * each core. This operation must be in m-mode.

nits: M-mode

> +        */
> +       if (CONFIG_IS_ENABLED(RISCV_MMODE))
> +               csr_write(CSR_U74_FEATURE_DISABLE, 0);
> +}

Otherwise,
Reviewed-by: Bin Meng <bmeng.cn at gmail.com>