[PATCH 20/20] interconnect: qcom: Divide clk rate by src node bus width

[Konrad Dybcio <konrad.dybcio@linaro.org>]

Ever since the introduction of SMD RPM ICC, we've been dividing the
clock rate by the wrong bus width. This has resulted in:

- setting wrong (mostly too low) rates, affecting performance
  - most often /2 or /4
  - things like DDR never hit their full potential
  - the rates were only correct if src bus width == dst bus width
    for all src, dst pairs on a given bus

- Qualcomm using the same wrong logic in their BSP driver in msm-5.x
  that ships in production devices today

- me losing my sanity trying to find this

Resolve it by using dst_qn, if it exists.

Fixes: 5e4e6c4d3ae0 ("interconnect: qcom: Add QCS404 interconnect provider driver")
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
---
 drivers/interconnect/qcom/icc-rpm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
index 59be704364bb..58e2a8b1b7c3 100644
--- a/drivers/interconnect/qcom/icc-rpm.c
+++ b/drivers/interconnect/qcom/icc-rpm.c
@@ -340,7 +340,7 @@ static void qcom_icc_bus_aggregate(struct icc_provider *provider,
 static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
 {
 	struct qcom_icc_provider *qp;
-	struct qcom_icc_node *src_qn = NULL, *dst_qn = NULL;
+	struct qcom_icc_node *src_qn = NULL, *dst_qn = NULL, *qn = NULL;
 	struct icc_provider *provider;
 	u64 active_rate, sleep_rate;
 	u64 agg_avg[QCOM_SMD_RPM_STATE_NUM], agg_peak[QCOM_SMD_RPM_STATE_NUM];
@@ -353,6 +353,8 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
 	provider = src->provider;
 	qp = to_qcom_provider(provider);
 
+	qn = dst_qn ? dst_qn : src_qn;
+
 	qcom_icc_bus_aggregate(provider, agg_avg, agg_peak, &max_agg_avg);
 
 	ret = qcom_icc_rpm_set(src_qn, agg_avg);
@@ -372,11 +374,11 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
 	/* Intentionally keep the rates in kHz as that's what RPM accepts */
 	active_rate = max(agg_avg[QCOM_SMD_RPM_ACTIVE_STATE],
 			  agg_peak[QCOM_SMD_RPM_ACTIVE_STATE]);
-	do_div(active_rate, src_qn->buswidth);
+	do_div(active_rate, qn->buswidth);
 
 	sleep_rate = max(agg_avg[QCOM_SMD_RPM_SLEEP_STATE],
 			 agg_peak[QCOM_SMD_RPM_SLEEP_STATE]);
-	do_div(sleep_rate, src_qn->buswidth);
+	do_div(sleep_rate, qn->buswidth);
 
 	/*
 	 * Downstream checks whether the requested rate is zero, but it makes little sense

-- 
2.40.1