linux-kernel - Re: [RFC PATCH] interconnect: qcom: icc-rpm: Don't call __qcom_icc

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Date:   Tue, 21 Mar 2023 21:30:48 +0200
From:   Georgi Djakov <djakov@...nel.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org
Cc:     marijn.suijten@...ainline.org,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] interconnect: qcom: icc-rpm: Don't call
 __qcom_icc_set twice on the same node

On 3.03.23 4:35, Konrad Dybcio wrote:
> Currently, when sync_state calls set(n, n) all the paths for setting
> parameters on an icc node are called twice. Avoid that.

This could be optimized indeed.

> Fixes: 751f4d14cdb4 ("interconnect: icc-rpm: Set destination bandwidth as well as source bandwidth")
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
> RFC comes from the fact that I *believe* this should be correct, but I'm
> not entirely sure about it..
> 
> 
>   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 a6e0de03f46b..d35db1af9b08 100644
> --- a/drivers/interconnect/qcom/icc-rpm.c
> +++ b/drivers/interconnect/qcom/icc-rpm.c
> @@ -387,7 +387,7 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>   	ret = __qcom_icc_set(src, src_qn, sum_bw);
>   	if (ret)
>   		return ret;
> -	if (dst_qn) {
> +	if (dst_qn && src_qn != dst_qn) {
>   		ret = __qcom_icc_set(dst, dst_qn, sum_bw);
>   		if (ret)
>   			return ret;

Today we also call provider->set(node, node) in icc_node_add() to set
the initial bandwidth when nodes are being added to the topology. The
above change will affect that as well.

BR,
Georgi