[PATCH v2] lib: utils: Make sure that hartid and the scratch are aligned

[Samuel Holland]

Hi Raj,

On 2025-02-13 1:52 PM, Raj Vishwanathan wrote:
> Harts associated with an ACLINT_MSWI need not have sequential hartids.
> It is insufficient to use first_hartid and hart_count. To account for
> non-sequential hart ids, include the empty hard-ids' generate hart-count.

This doesn't help, because the expression (hartid - first_hartid) is still used
to calculate MMIO addresses. See for example mtimer_event_start() and
mswi_ipi_send(). If there is a gap in the hartids mapped to the ACLINT
MTIMER/MSWI indexes, these functions will compute the wrong MMIO address and
fail to set the timer or send an IPI.

Either each device instance needs an array of [ACLINT index] => [hart index]
mappings, or the ACLINT index needs to be recorded separately in a new per-hart
scratch variable.

Regards,
Samuel

> Signed-off-by: Raj Vishwanathan <Raj.Vishwanathan at gmail.com>
> ---
> 
> hart_count = last_hart_id - first_hart_id +1
> count = number of harts
> For sequential hart_id's, count = hart_count
> For non-sequential hart_id's, count  < hart_count
> ---
>  lib/utils/fdt/fdt_helper.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
> index cb350e5..bb3fddd 100644
> --- a/lib/utils/fdt/fdt_helper.c
> +++ b/lib/utils/fdt/fdt_helper.c
> @@ -1046,8 +1046,7 @@ int fdt_parse_aclint_node(const void *fdt, int nodeoffset,
>  
>  	if ((last_hartid >= first_hartid) && first_hartid != -1U) {
>  		*out_first_hartid = first_hartid;
> -		count = last_hartid - first_hartid + 1;
> -		*out_hart_count = (hart_count < count) ? hart_count : count;
> +		*out_hart_count  = last_hartid - first_hartid + 1;
>  	}
>  
>  	return 0;