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    SubjectRe: [PATCH v2 19/22] interconnect: qcom: icc-rpm: Fix bucket number
    On Fri, Jun 09, 2023 at 10:19:24PM +0200, Konrad Dybcio wrote:
    > SMD RPM only provides two buckets, one each for the active-only and
    > active-sleep RPM contexts. Use the correct constant to allocate and
    > operate on them.
    >
    > Fixes: dcbce7b0a79c ("interconnect: qcom: icc-rpm: Support multiple buckets")
    > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
    > Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
    > ---
    > drivers/interconnect/qcom/icc-rpm.c | 14 +++++++-------
    > 1 file changed, 7 insertions(+), 7 deletions(-)
    >
    > diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
    > index 6d40815c5401..3ac47b818afe 100644
    > --- a/drivers/interconnect/qcom/icc-rpm.c
    > +++ b/drivers/interconnect/qcom/icc-rpm.c
    > [...]
    > @@ -275,7 +275,7 @@ static int qcom_icc_bw_aggregate(struct icc_node *node, u32 tag, u32 avg_bw,
    > if (!tag)
    > tag = QCOM_ICC_TAG_ALWAYS;
    >
    > - for (i = 0; i < QCOM_ICC_NUM_BUCKETS; i++) {
    > + for (i = 0; i < QCOM_SMD_RPM_STATE_NUM; i++) {
    > if (tag & BIT(i)) {

    Hm, I think QCOM_ICC_NUM_BUCKETS is actually intentional here. There is
    a hint about this in the description of the commit in your Fixes line:

    > This patch studies the implementation from interconnect rpmh driver to
    > support multiple buckets. The rpmh driver provides three buckets for
    > AMC, WAKE, and SLEEP; this driver only needs to use WAKE and SLEEP
    > buckets, but we keep the same way with rpmh driver, this can allow us
    > to reuse the DT binding and avoid to define duplicated data structures.

    As far as I understand, the idea was to reuse the definitions in
    qcom,icc.h and just ignore the AMC bucket for now. AFAIU AMC (or rather
    the lack thereof) is basically caching: Sending requests without AMC bit
    set is delayed until the next rpmh_flush() call that happens when
    entering a deep idle state. It requires some work but I guess
    theoretically one could implement exactly the same for RPM.

    What you're actually doing here is not fixing the commit but changing
    the bindings. On MSM8909 I defined the ICC path for CPU<->RAM like this:

    interconnects = <&bimc MAS_APPS_PROC QCOM_ICC_TAG_ACTIVE_ONLY
    &bimc SLV_EBI QCOM_ICC_TAG_ACTIVE_ONLY>;

    Per definition in qcom,icc.h:

    QCOM_ICC_TAG_ACTIVE_ONLY = (AMC | WAKE) = (BIT(0) | BIT(1))

    Without your patch series this behaves correctly. It results in an
    active-only vote.

    The change of behavior is in PATCH 17/22 "interconnect: qcom: icc-rpm:
    Control bus rpmcc from icc". It silently switches from
    QCOM_ICC_BUCKET_WAKE (1) and QCOM_ICC_BUCKET_SLEEP (2) to
    QCOM_SMD_RPM_ACTIVE_STATE (0) and QCOM_SMD_RPM_SLEEP_STATE (1).

    In other words, QCOM_ICC_TAG_ACTIVE_ONLY (BIT(0) | BIT(1)) now results
    in an active+sleep vote, not an active-only one. :)

    There doesn't seem to be an upstream user of the ICC tags/buckets for
    icc-rpm yet so personally I would be fine with changing it. However,
    then qcom,icc.h should get a clear comment that it's rpmh-only and we
    should define a new qcom,icc-rpm.h.

    Or perhaps we should just drop this patch and continue using
    QCOM_ICC_BUCKET_WAKE and QCOM_ICC_BUCKET_SLEEP as before?

    Thanks,
    Stephan

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