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

Mike Tipton
2020-07-02T21:02:46Z

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@codeaurora.org>
>> ---
>> 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
>