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

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Date:   Fri, 3 Mar 2023 12:36:00 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org
Cc:     marijn.suijten@...ainline.org, Georgi Djakov <djakov@...nel.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 3.03.2023 12:35, Bryan O'Donoghue wrote:
> On 03/03/2023 11:33, Konrad Dybcio wrote:
>>
>>
>> On 3.03.2023 12:32, Bryan O'Donoghue wrote:
>>> On 03/03/2023 02:35, 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.
>>>>
>>>> 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;
>>>
>>> Is it possible for src_qn == dst_qn ?
>> As the commit message says, sync_state calls set(n, n) in
>> drivers/interconnect/core.c : icc_sync_state(struct device *dev)
> 
> So you've _seen_ that happen ?
Yes, I did, on every boot previous to this patch, I believe.

Konrad
>