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

[Mike Tipton]

On 7/2/2020 4:11 AM, Georgi Djakov wrote:
> 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.
I can change base to a u32. It doesn't need anything more than that.

> > +
> > +	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