linux-kernel - [PATCH v4 1/6] interconnect: qcom: Fix small BW votes being truncated to zero

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Date:   Thu,  3 Sep 2020 12:21:44 -0700
From:   Mike Tipton <mdtipton@...eaurora.org>
To:     georgi.djakov@...aro.org
Cc:     bjorn.andersson@...aro.org, agross@...nel.org,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Tipton <mdtipton@...eaurora.org>
Subject: [PATCH v4 1/6] interconnect: qcom: Fix small BW votes being truncated to zero

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@...eaurora.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 a3d2ef1d9903..609db9c95fd7 100644
--- a/drivers/interconnect/qcom/bcm-voter.c
+++ b/drivers/interconnect/qcom/bcm-voter.c
@@ -52,8 +52,20 @@ static int cmp_vcd(void *priv, struct list_head *a, struct list_head *b)
 		return 1;
 }
 
+static u64 bcm_div(u64 num, u32 base)
+{
+	/* Ensure that small votes aren't lost. */
+	if (num && num < base)
+		return 1;
+
+	do_div(num, base);
+
+	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};
@@ -61,22 +73,21 @@ 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] * 1000ULL;
-		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] * 1000ULL;
-		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 &&
-- 
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