[PATCH] lib: sbi: Fix writes to emulated 32-bit htimedelta CSR

[Anup Patel]

On Fri, Aug 30, 2024 at 1:38 AM Samuel Holland
<samuel.holland at sifive.com> wrote:
>
> Writes to the low half CSR should not affect the high half of the value.
> Make this separation explicit by writing to the delta in memory as two
> adjacent XLEN-sized values.
>
> Fixes: 1e9f88889f8b ("lib: Emulate HTIMEDELTA CSR for platforms not having TIME CSR")
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>

Good catch. LGTM.

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

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>
>  include/sbi/sbi_timer.h |  2 ++
>  lib/sbi/sbi_timer.c     | 15 ++++++++-------
>  2 files changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/include/sbi/sbi_timer.h b/include/sbi/sbi_timer.h
> index ac48e2b8..ac2c7be5 100644
> --- a/include/sbi/sbi_timer.h
> +++ b/include/sbi/sbi_timer.h
> @@ -78,8 +78,10 @@ u64 sbi_timer_get_delta(void);
>  /** Set timer delta value for current HART */
>  void sbi_timer_set_delta(ulong delta);
>
> +#if __riscv_xlen == 32
>  /** Set upper 32-bits of timer delta value for current HART */
>  void sbi_timer_set_delta_upper(ulong delta_upper);
> +#endif
>
>  /** Start timer event for current HART */
>  void sbi_timer_event_start(u64 next_event);
> diff --git a/lib/sbi/sbi_timer.c b/lib/sbi/sbi_timer.c
> index 7b618de1..32955183 100644
> --- a/lib/sbi/sbi_timer.c
> +++ b/lib/sbi/sbi_timer.c
> @@ -114,20 +114,21 @@ u64 sbi_timer_get_delta(void)
>
>  void sbi_timer_set_delta(ulong delta)
>  {
> -       u64 *time_delta = sbi_scratch_offset_ptr(sbi_scratch_thishart_ptr(),
> -                                                time_delta_off);
> +       ulong *time_delta = sbi_scratch_offset_ptr(sbi_scratch_thishart_ptr(),
> +                                                  time_delta_off);
>
> -       *time_delta = (u64)delta;
> +       *time_delta = delta;
>  }
>
> +#if __riscv_xlen == 32
>  void sbi_timer_set_delta_upper(ulong delta_upper)
>  {
> -       u64 *time_delta = sbi_scratch_offset_ptr(sbi_scratch_thishart_ptr(),
> -                                                time_delta_off);
> +       ulong *time_delta = sbi_scratch_offset_ptr(sbi_scratch_thishart_ptr(),
> +                                                  time_delta_off);
>
> -       *time_delta &= 0xffffffffULL;
> -       *time_delta |= ((u64)delta_upper << 32);
> +       *(time_delta + 1) = delta_upper;
>  }
> +#endif
>
>  void sbi_timer_event_start(u64 next_event)
>  {
> --
> 2.45.1
>
>
> --
> opensbi mailing list
> opensbi at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/opensbi