linux-kernel - Re: [PATCH v7 2/9] interconnect: qcom: rpm: Add support for specifying channel num

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Message-ID: <101834f0-e00c-5469-c8a5-59a00a5160a5@linaro.org>
Date:   Tue, 21 Mar 2023 15:23:44 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Georgi Djakov <djakov@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/9] interconnect: qcom: rpm: Add support for
 specifying channel num



On 21.03.2023 15:21, Georgi Djakov wrote:
> On 21.03.23 16:09, Konrad Dybcio wrote:
>>
>> On 21.03.2023 15:06, Georgi Djakov wrote:
>>> Hi Konrad,
>>>
>>> Thanks for the patch!
>>>
>>> On 8.03.23 23:40, Konrad Dybcio wrote:
>>>> Some nodes, like EBI0 (DDR) or L3/LLCC, may be connected over more than
>>>> one channel. This should be taken into account in bandwidth calcualtion,
>>>> as we're supposed to feed msmbus with the per-channel bandwidth. Add
>>>> support for specifying that and use it during bandwidth aggregation.
>>>>
>>>
>>> This looks good, but do you have any follow-up patch to use this and set
>>> the channels in some driver?
>> Yes, I have a couple of OOT drivers that are gonna make use of it.
>> TBF it should have been sent separately from the QoS mess, but I
>> don't think it's much of an issue to take it as-is.
>>
>> The aforementioned OOT drivers for MSM8998 and SM6375 will be
>> submitted after we reach a consensus on how we want to ensure
>> that each node is guaranteed to have its clocks enabled before
>> access, among some other minor things.
> 
> Yes, these QoS clocks are confusing. Maybe you can even submit them
> without configuring any QoS stuff in first place? Does enabling QoS
> actually show any benefits on these devices?
Haven't tested that thoroughly to be honest. But I'll try to get
some numbers.

Konrad
> 
> Thanks,
> Georgi
> 
>> Konrad
>>>
>>> BR,
>>> Georgi
>>>
>>>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>> ---
>>>>    drivers/interconnect/qcom/icc-rpm.c | 7 ++++++-
>>>>    drivers/interconnect/qcom/icc-rpm.h | 2 ++
>>>>    2 files changed, 8 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
>>>> index 35fd75ae70e3..27c4c6497994 100644
>>>> --- a/drivers/interconnect/qcom/icc-rpm.c
>>>> +++ b/drivers/interconnect/qcom/icc-rpm.c
>>>> @@ -317,6 +317,7 @@ static void qcom_icc_bus_aggregate(struct icc_provider *provider,
>>>>    {
>>>>        struct icc_node *node;
>>>>        struct qcom_icc_node *qn;
>>>> +    u64 sum_avg[QCOM_ICC_NUM_BUCKETS];
>>>>        int i;
>>>>          /* Initialise aggregate values */
>>>> @@ -334,7 +335,11 @@ static void qcom_icc_bus_aggregate(struct icc_provider *provider,
>>>>        list_for_each_entry(node, &provider->nodes, node_list) {
>>>>            qn = node->data;
>>>>            for (i = 0; i < QCOM_ICC_NUM_BUCKETS; i++) {
>>>> -            agg_avg[i] += qn->sum_avg[i];
>>>> +            if (qn->channels)
>>>> +                sum_avg[i] = div_u64(qn->sum_avg[i], qn->channels);
>>>> +            else
>>>> +                sum_avg[i] = qn->sum_avg[i];
>>>> +            agg_avg[i] += sum_avg[i];
>>>>                agg_peak[i] = max_t(u64, agg_peak[i], qn->max_peak[i]);
>>>>            }
>>>>        }
>>>> diff --git a/drivers/interconnect/qcom/icc-rpm.h b/drivers/interconnect/qcom/icc-rpm.h
>>>> index 8ba1918d7997..8aed5400afda 100644
>>>> --- a/drivers/interconnect/qcom/icc-rpm.h
>>>> +++ b/drivers/interconnect/qcom/icc-rpm.h
>>>> @@ -66,6 +66,7 @@ struct qcom_icc_qos {
>>>>     * @id: a unique node identifier
>>>>     * @links: an array of nodes where we can go next while traversing
>>>>     * @num_links: the total number of @links
>>>> + * @channels: number of channels at this node (e.g. DDR channels)
>>>>     * @buswidth: width of the interconnect between a node and the bus (bytes)
>>>>     * @sum_avg: current sum aggregate value of all avg bw requests
>>>>     * @max_peak: current max aggregate value of all peak bw requests
>>>> @@ -78,6 +79,7 @@ struct qcom_icc_node {
>>>>        u16 id;
>>>>        const u16 *links;
>>>>        u16 num_links;
>>>> +    u16 channels;
>>>>        u16 buswidth;
>>>>        u64 sum_avg[QCOM_ICC_NUM_BUCKETS];
>>>>        u64 max_peak[QCOM_ICC_NUM_BUCKETS];
>>>>
>>>
>