Re: [PATCH net-next 03/10] net: microchip: sparx5: add support for Service Dual Leacky Buckets

Simon Horman
2023-02-04T12:53:44Z

On Thu, Feb 02, 2023 at 11:43:48AM +0100, Daniel Machon wrote:
> Add support for Service Dual Leacky Buckets (SDLB), used to implement
> PSFP flow-meters. Buckets are linked together in a leak chain of a leak
> group. Leak groups a preconfigured to serve buckets within a certain
> rate interval.
>
> Signed-off-by: Daniel Machon <daniel.machon@microchip.com>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

...

> diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_sdlb.c b/drivers/net/ethernet/microchip/sparx5/sparx5_sdlb.c
> new file mode 100644
> index 000000000000..f5267218caeb
> --- /dev/null
> +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_sdlb.c

...

> +static u32 sparx5_sdlb_group_get_next(struct sparx5 *sparx5, u32 group,
> + u32 lb)
> +{
> + u32 val;
> +
> + val = spx5_rd(sparx5, ANA_AC_SDLB_XLB_NEXT(lb));
> +
> + return ANA_AC_SDLB_XLB_NEXT_LBSET_NEXT_GET(val);
> +}

...

> +static u32 sparx5_sdlb_group_get_last(struct sparx5 *sparx5, u32 group)
> +{
> + u32 itr, next;
> +
> + itr = sparx5_sdlb_group_get_first(sparx5, group);
> +
> + for (;;) {

Unbounded loops like this give me some apprehension.
Will they always terminate?

> + next = sparx5_sdlb_group_get_next(sparx5, group, itr);
> + if (itr == next)
> + return itr;
> +
> + itr = next;
> + }
> +}

...

> +static int sparx5_sdlb_group_get_adjacent(struct sparx5 *sparx5, u32 group,
> + u32 idx, u32 *prev, u32 *next,
> + u32 *first)
> +{
> + u32 itr;
> +
> + *first = sparx5_sdlb_group_get_first(sparx5, group);
> + *prev = *first;
> + *next = *first;
> + itr = *first;
> +
> + for (;;) {
> + *next = sparx5_sdlb_group_get_next(sparx5, group, itr);
> +
> + if (itr == idx)
> + return 0; /* Found it */
> +
> + if (itr == *next)
> + return -EINVAL; /* Was not found */
> +
> + *prev = itr;
> + itr = *next;
> + }
> +}
> +
> +static int sparx5_sdlb_group_get_count(struct sparx5 *sparx5, u32 group)
> +{
> + u32 itr, next;
> + int count = 0;
> +
> + itr = sparx5_sdlb_group_get_first(sparx5, group);
> +
> + for (;;) {
> + next = sparx5_sdlb_group_get_next(sparx5, group, itr);
> + if (itr == next)
> + return count;
> +
> + itr = next;
> + count++;
> + }
> +}

...

> +int sparx5_sdlb_group_get_by_index(struct sparx5 *sparx5, u32 idx, u32 *group)
> +{
> + u32 itr, next;
> + int i;
> +
> + for (i = 0; i < SPX5_SDLB_GROUP_CNT; i++) {
> + if (sparx5_sdlb_group_is_empty(sparx5, i))
> + continue;
> +
> + itr = sparx5_sdlb_group_get_first(sparx5, i);
> +
> + for (;;) {
> + next = sparx5_sdlb_group_get_next(sparx5, i, itr);
> +
> + if (itr == idx) {
> + *group = i;
> + return 0; /* Found it */
> + }
> + if (itr == next)
> + break; /* Was not found */
> +
> + itr = next;
> + }
> + }
> +
> + return -EINVAL;
> +}

...