linux-kernel - Re: [PATCH RFT] interconnect: qcom: icc-rpm: Fix peak rate calculation

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Date:   Wed, 6 Dec 2023 13:19:56 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Georgi Djakov <djakov@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH RFT] interconnect: qcom: icc-rpm: Fix peak rate
 calculation



On 12/5/23 23:14, Bjorn Andersson wrote:
> Per the commit message of commit 'dd014803f260 ("interconnect: qcom:
> icc-rpm: Add AB/IB calculations coefficients")', the peak rate should be
> 100/ib_percent. But, in what looks like a typical typo, the numerator
> value is discarded in the calculation.
> 
> Update the implementation to match the described intention.
> 
> Fixes: dd014803f260 ("interconnect: qcom: icc-rpm: Add AB/IB calculations coefficients")
> Cc: stable@...r.kernel.org
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> ---
> Spotted while reading the code, patch is untested.
> ---
>   drivers/interconnect/qcom/icc-rpm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
> index fb54e78f8fd7..a8ed435f696c 100644
> --- a/drivers/interconnect/qcom/icc-rpm.c
> +++ b/drivers/interconnect/qcom/icc-rpm.c
> @@ -307,7 +307,7 @@ static u64 qcom_icc_calc_rate(struct qcom_icc_provider *qp, struct qcom_icc_node
>   
>   	if (qn->ib_coeff) {
>   		agg_peak_rate = qn->max_peak[ctx] * 100;
> -		agg_peak_rate = div_u64(qn->max_peak[ctx], qn->ib_coeff);
> +		agg_peak_rate = div_u64(agg_peak_rate, qn->ib_coeff);
Oh fun.. I'dve assumed the compiler is smart enough to catch this

Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad