linux-kernel - Re: [PATCH 1/4] interconnect: qcom: rpm: Don't set QoS params before non-zero bw is requested

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Message-ID: <735088f7-2888-04b1-7751-a3ad7e13a857@linaro.org>
Date:   Tue, 3 Jan 2023 23:07:46 +0000
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org, krzysztof.kozlowski@...aro.org
Cc:     marijn.suijten@...ainline.org, Georgi Djakov <djakov@...nel.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] interconnect: qcom: rpm: Don't set QoS params before
 non-zero bw is requested

On 03/01/2023 17:30, Konrad Dybcio wrote:
> Until now, the icc-rpm driver unconditionally set QoS params, even on
> empty requests. This is superfluous and the downstream counterpart does
> not do it. Follow it by doing the same.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>   drivers/interconnect/qcom/icc-rpm.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
> index 43b9ce0dcb6a..06e0fee547ab 100644
> --- a/drivers/interconnect/qcom/icc-rpm.c
> +++ b/drivers/interconnect/qcom/icc-rpm.c
> @@ -193,6 +193,12 @@ static int qcom_icc_qos_set(struct icc_node *node, u64 sum_bw)
>   	struct qcom_icc_provider *qp = to_qcom_provider(node->provider);
>   	struct qcom_icc_node *qn = node->data;
>   
> +	/* Defer setting QoS until the first non-zero bandwidth request. */
> +	if (!(node->avg_bw || node->peak_bw)) {
> +		dev_dbg(node->provider->dev, "NOT Setting QoS for %s\n", qn->name);
> +		return 0;
> +	}
> +
>   	dev_dbg(node->provider->dev, "Setting QoS for %s\n", qn->name);
>   
>   	switch (qp->type) {

Doesn't downstream clear the registers on a zero allocation request ?

https://git.codelinaro.org/clo/la/kernel/msm-3.18/-/blob/LA.BR.1.2.9-00810-8x09.0/drivers/platform/msm/msm_bus/msm_bus_bimc.c#L1302

https://git.codelinaro.org/clo/la/kernel/msm-3.18/-/blob/LA.BR.1.2.9-00810-8x09.0/drivers/platform/msm/msm_bus/msm_bus_bimc.c#L1318

https://git.codelinaro.org/clo/la/kernel/msm-3.18/-/blob/LA.BR.1.2.9-00810-8x09.0/drivers/platform/msm/msm_bus/msm_bus_bimc.c#L1367

msm_bus_bimc_set_qos_bw()
{
	/* Only calculate if there's a requested bandwidth and window */
	if (qbw->bw && qbw->ws) {
	}else
		/* Clear bandwidth registers */
		set_qos_bw_regs(base, mas_index, 0, 0, 0, 0, 0);
}

---
bod