[PATCH] lib: sbi_hart: clear mip csr during hart init

[Anup Patel]

On Sat, Mar 25, 2023 at 10:21 PM Mayuresh Chitale
<mchitale at ventanamicro.com> wrote:
>
> If mip.SEIP bit is not cleared then on HiFive Unmatched board it causes
> spurious external interrupts. This breaks the boot up of HiFive Unmatched
> board. Hence it is required to bring the mip CSR to a known state during
> hart init and avoid spurious interrupts.
>
> Fixes: d9e7368 ("firmware: Not to clear all the MIP")
> Signed-off-by: Mayuresh Chitale <mchitale at ventanamicro.com>

Looks good to me.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>  firmware/fw_base.S | 7 -------
>  lib/sbi/sbi_hart.c | 6 ++++++
>  2 files changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/firmware/fw_base.S b/firmware/fw_base.S
> index ceef44f..5a3e894 100644
> --- a/firmware/fw_base.S
> +++ b/firmware/fw_base.S
> @@ -430,13 +430,6 @@ _start_warm:
>
>         /* Disable all interrupts */
>         csrw    CSR_MIE, zero
> -       /*
> -        * Only clear the MIP_SSIP and MIP_STIP. For the platform like QEMU,
> -        * If we clear other interrupts like MIP_SEIP and the pendings of
> -        * PLIC still exist, the QEMU may not set it back immediately.
> -        */
> -       li      t0, (MIP_SSIP | MIP_STIP)
> -       csrc    CSR_MIP, t0
>
>         /* Find HART count and HART stack size */
>         lla     a4, platform
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 5e06918..6e52cbd 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -733,6 +733,12 @@ int sbi_hart_init(struct sbi_scratch *scratch, bool cold_boot)
>  {
>         int rc;
>
> +       /*
> +        * Clear mip CSR before proceeding with init to avoid any spurious
> +        * external interrupts in S-mode.
> +        */
> +       csr_write(CSR_MIP, 0);
> +
>         if (cold_boot) {
>                 if (misa_extension('H'))
>                         sbi_hart_expected_trap = &__sbi_expected_trap_hext;
> --
> 2.34.1
>
>
> --
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