Re: [PATCH 4/4] interconnect: qcom: Fix small BW votes being truncated to zero

[Georgi Djakov]

Hi Mike,

On 6/23/20 07:08, Mike Tipton wrote:
> Small BW votes that translate to less than a single BCM unit are
> currently truncated to zero. Ensure that non-zero BW requests always
> result in at least a vote of 1 to BCM.
> 
> Fixes: 976daac4a1c5 ("interconnect: qcom: Consolidate interconnect RPMh support")
> Signed-off-by: Mike Tipton <mdtipton@xxxxxxxxxxxxxx>
> ---
>  drivers/interconnect/qcom/bcm-voter.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/interconnect/qcom/bcm-voter.c b/drivers/interconnect/qcom/bcm-voter.c
> index a68c858ca6b7..9e2612fe7fad 100644
> --- a/drivers/interconnect/qcom/bcm-voter.c
> +++ b/drivers/interconnect/qcom/bcm-voter.c
> @@ -54,8 +54,20 @@ static int cmp_vcd(void *priv, struct list_head *a, struct list_head *b)
>  		return 1;
>  }
>  
> +static u64 bcm_div(u64 num, u64 base)
> +{
> +	/* Ensure that small votes aren't lost. */
> +	if (num && num < base)
> +		return 1;
> +
> +	do_div(num, base);

do_div() does a 64-by-32 division, which will truncate these to 32-bit.

> +
> +	return num;
> +}
> +
>  static void bcm_aggregate(struct qcom_icc_bcm *bcm)
>  {
> +	struct qcom_icc_node *node;
>  	size_t i, bucket;
>  	u64 agg_avg[QCOM_ICC_NUM_BUCKETS] = {0};
>  	u64 agg_peak[QCOM_ICC_NUM_BUCKETS] = {0};
> @@ -63,22 +75,21 @@ static void bcm_aggregate(struct qcom_icc_bcm *bcm)
>  
>  	for (bucket = 0; bucket < QCOM_ICC_NUM_BUCKETS; bucket++) {
>  		for (i = 0; i < bcm->num_nodes; i++) {
> -			temp = bcm->nodes[i]->sum_avg[bucket] * bcm->aux_data.width;
> -			do_div(temp, bcm->nodes[i]->buswidth * bcm->nodes[i]->channels);
> +			node = bcm->nodes[i];
> +			temp = bcm_div(node->sum_avg[bucket] * bcm->aux_data.width,
> +				       node->buswidth * node->channels);
>  			agg_avg[bucket] = max(agg_avg[bucket], temp);
>  
> -			temp = bcm->nodes[i]->max_peak[bucket] * bcm->aux_data.width;
> -			do_div(temp, bcm->nodes[i]->buswidth);
> +			temp = bcm_div(node->max_peak[bucket] * bcm->aux_data.width,
> +				       node->buswidth);
>  			agg_peak[bucket] = max(agg_peak[bucket], temp);
>  		}
>  
>  		temp = agg_avg[bucket] * bcm->vote_scale;
> -		do_div(temp, bcm->aux_data.unit);
> -		bcm->vote_x[bucket] = temp;
> +		bcm->vote_x[bucket] = bcm_div(temp, bcm->aux_data.unit);
>  
>  		temp = agg_peak[bucket] * bcm->vote_scale;
> -		do_div(temp, bcm->aux_data.unit);
> -		bcm->vote_y[bucket] = temp;
> +		bcm->vote_y[bucket] = bcm_div(temp, bcm->aux_data.unit);
>  	}
>  
>  	if (bcm->keepalive && bcm->vote_x[QCOM_ICC_BUCKET_AMC] == 0 &&
> 

The rest looks good.

Thanks,
Georgi