Hi Yao,
On 09:21 Sat 02 Aug , Yao Zi wrote:
> Add an alternative implementation that use Zalrsc extension only for
> HART lottery and SMP locking to support SMP on cores without "Zaamo"
> extension available. The Zaamo implementation is still used by default
> since since the Zalrsc one requires more instructions.
~~~~~~~~~~~~~two 'since'
to slightly improve it..
.., The Zaamo implementation is prioritized selected if both extension
available,
since the Zalrsc one requires more instructions.
while I can understand the logic, but if we interpret from the code below,
it's a little bit weird:
if (RISCV_ISA_ZAAMO) not enabled:
use zalrsc implementation
instead of
if (RISCV_ISA_ZALRSC) is enabled:
use zalrsc implementation
I mean, to select Zalrsc implementation, enabling RISCV_ISA_ZALRSC is not
enough,
but RISCV_ISA_ZAAMO should be explicitly disabled, in fact RISCV_ISA_ZALRSC is
superfluous here
make it further, it would be great if we could do some Kconfig sanity check..
(I have one more comment for configs/ibex-ast2700_defconfig in patch 1/2)
>
> Signed-off-by: Yao Zi <zi...@disroot.org>
> ---
> arch/riscv/cpu/start.S | 26 +++++++++++++++++++++++++-
> 1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
> index 7bafdfd390a..6324ff585d4 100644
> --- a/arch/riscv/cpu/start.S
> +++ b/arch/riscv/cpu/start.S
> @@ -151,8 +151,15 @@ call_harts_early_init:
> */
> la t0, hart_lottery
> li t1, 1
> +#if CONFIG_IS_ENABLED
> amoswap.w s2, t1, 0(t0)
> bnez s2, wait_for_gd_init
> +#else
> + lr.w s2, (t0)
> + bnez s2, wait_for_gd_init
> + sc.w s2, t1, (t0)
> + bnez s2, wait_for_gd_init
> +#endif
> #else
> /*
> * FIXME: gp is set before it is initialized. If an XIP U-Boot ever
> @@ -177,7 +184,12 @@ call_harts_early_init:
> #if !CONFIG_IS_ENABLED(XIP)
> #ifdef CONFIG_AVAILABLE_HARTS
> la t0, available_harts_lock
> +#if CONFIG_IS_ENABLED(RISCV_ISA_ZAAMO)
> amoswap.w.rl zero, zero, 0(t0)
> +#else
> + fence rw, w
> + sw zero, 0(t0)
> +#endif
> #endif
>
> wait_for_gd_init:
> @@ -190,7 +202,14 @@ wait_for_gd_init:
> #ifdef CONFIG_AVAILABLE_HARTS
> la t0, available_harts_lock
> li t1, 1
> -1: amoswap.w.aq t1, t1, 0(t0)
> +1:
> +#if CONFIG_IS_ENABLED(RISCV_ISA_ZAAMO)
> + amoswap.w.aq t1, t1, 0(t0)
> +#else
> + lr.w.aq t1, 0(t0)
> + bnez t1, 1b
> + sc.w.rl t1, t1, 0(t0)
> +#endif
> bnez t1, 1b
>
> /* register available harts in the available_harts mask */
> @@ -200,7 +219,12 @@ wait_for_gd_init:
> or t2, t2, t1
> SREG t2, GD_AVAILABLE_HARTS(gp)
>
> +#if CONFIG_IS_ENABLED(RISCV_ISA_ZAAMO)
> amoswap.w.rl zero, zero, 0(t0)
> +#else
> + fence rw, w
> + sw zero, 0(t0)
> +#endif
> #endif
>
> /*
> --
> 2.50.1
>
--
Yixun Lan (dlan)
