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Message-ID: <4417edef-5d4d-e802-69fb-feeeb2304e44@linaro.org>
Date: Wed, 14 Jun 2023 00:40:11 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Stephan Gerhold <stephan@...hold.net>
Cc: Andy Gross <agross@...nel.org>,
Bjorn Andersson <andersson@...nel.org>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>,
Georgi Djakov <djakov@...nel.org>,
Leo Yan <leo.yan@...aro.org>,
Evan Green <evgreen@...omium.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Marijn Suijten <marijn.suijten@...ainline.org>,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-clk@...r.kernel.org, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v4 17/22] interconnect: qcom: icc-rpm: Control bus rpmcc
from icc
On 13.06.2023 22:36, Stephan Gerhold wrote:
> On Tue, Jun 13, 2023 at 04:03:17PM +0200, Konrad Dybcio wrote:
>> The sole purpose of bus clocks that were previously registered with
>> rpmcc was to convey the aggregated bandwidth to RPM. There's no good
>> reason to keep them outside the interconnect framework, as it only
>> adds to the plentiful complexity.
>>
>> Add the required code to handle these clocks from within SMD RPM ICC.
>>
>> RPM-owned bus clocks are no longer considered a thing, but sadly we
>> have to allow for the existence of HLOS-owned bus clocks, as some
>> (mostly older) SoCs (ab)use these for bus scaling (e.g. MSM8998 and
>> &mmcc AHB_CLK_SRC).
>>
>> This in turn is trivially solved with a single *clk, which is filled
>> and used iff qp.bus_clk_desc is absent and we have a "bus" clock-names
>> entry in the DT node.
>>
>> This change should(tm) be fully compatible with all sorts of old
>> Device Trees as far as the interconnect functionality goes (modulo
>> abusing bus clock handles or wrongly using the qcom,icc.h binding,
>> but that's a mistake in and of itself).
>>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>> ---
>> drivers/interconnect/qcom/icc-rpm.c | 119 ++++++++++++++++++++----------------
>> drivers/interconnect/qcom/icc-rpm.h | 13 ++--
>> drivers/interconnect/qcom/msm8996.c | 1 -
>> drivers/interconnect/qcom/sdm660.c | 1 -
>> 4 files changed, 71 insertions(+), 63 deletions(-)
>>
>> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
>> index b8ecf9538ab9..f9d0ecba5631 100644
>> --- a/drivers/interconnect/qcom/icc-rpm.c
>> +++ b/drivers/interconnect/qcom/icc-rpm.c
>> @@ -49,7 +49,7 @@
>> #define NOC_QOS_MODE_FIXED_VAL 0x0
>> #define NOC_QOS_MODE_BYPASS_VAL 0x2
>>
>> -#define ICC_BUS_CLK_MIN_RATE 19200000ULL
>> +#define ICC_BUS_CLK_MIN_RATE 19200ULL /* kHz */
>>
>> static int qcom_icc_set_qnoc_qos(struct icc_node *src)
>> {
>> @@ -338,11 +338,10 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>> struct qcom_icc_node *src_qn = NULL, *dst_qn = NULL;
>> struct icc_provider *provider;
>> u64 sum_bw;
>> - u64 rate;
>> + u64 active_rate, sleep_rate;
>> u64 agg_avg[QCOM_ICC_NUM_BUCKETS], agg_peak[QCOM_ICC_NUM_BUCKETS];
>> u64 max_agg_avg;
>> - int ret, i;
>> - int bucket;
>> + int ret;
>>
>> src_qn = src->data;
>> if (dst)
>> @@ -364,49 +363,59 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>> return ret;
>> }
>>
>> - for (i = 0; i < qp->num_bus_clks; i++) {
>> - /*
>> - * Use WAKE bucket for active clock, otherwise, use SLEEP bucket
>> - * for other clocks. If a platform doesn't set interconnect
>> - * path tags, by default use sleep bucket for all clocks.
>> - *
>> - * Note, AMC bucket is not supported yet.
>> - */
>> - if (!strcmp(qp->bus_clks[i].id, "bus_a"))
>> - bucket = QCOM_ICC_BUCKET_WAKE;
>> - else
>> - bucket = QCOM_ICC_BUCKET_SLEEP;
>> -
>> - rate = icc_units_to_bps(max(agg_avg[bucket], agg_peak[bucket]));
>> - do_div(rate, src_qn->buswidth);
>> - rate = min_t(u64, rate, LONG_MAX);
>> -
>> - /*
>> - * Downstream checks whether the requested rate is zero, but it makes little sense
>> - * to vote for a value that's below the lower threshold, so let's not do so.
>> - */
>> - if (bucket == QCOM_ICC_BUCKET_WAKE && qp->keep_alive)
>> - rate = max(ICC_BUS_CLK_MIN_RATE, rate);
>> -
>> - if (qp->bus_clk_rate[i] == rate)
>> - continue;
>> -
>> - ret = clk_set_rate(qp->bus_clks[i].clk, rate);
>> - if (ret) {
>> - pr_err("%s clk_set_rate error: %d\n",
>> - qp->bus_clks[i].id, ret);
>> + /* Some providers don't have a bus clock to scale */
>> + if (!qp->bus_clk_desc && !qp->bus_clk)
>> + return 0;
>> +
>> + /* Intentionally keep the rates in kHz as that's what RPM accepts */
>> + active_rate = max(agg_avg[QCOM_SMD_RPM_ACTIVE_STATE],
>> + agg_peak[QCOM_SMD_RPM_ACTIVE_STATE]);
>> + do_div(active_rate, src_qn->buswidth);
>> +
>> + sleep_rate = max(agg_avg[QCOM_SMD_RPM_SLEEP_STATE],
>> + agg_peak[QCOM_SMD_RPM_SLEEP_STATE]);
>> + do_div(sleep_rate, src_qn->buswidth);
>> +
>> + /*
>> + * Downstream checks whether the requested rate is zero, but it makes little sense
>> + * to vote for a value that's below the lower threshold, so let's not do so.
>> + */
>> + if (qp->keep_alive)
>> + active_rate = max(ICC_BUS_CLK_MIN_RATE, active_rate);
>> +
>> + /* Some providers have a non-RPM-owned bus clock - convert kHz->Hz for the CCF */
>> + if (qp->bus_clk) {
>> + active_rate = max_t(u64, active_rate, sleep_rate);
>> + /* ARM32 caps clk_set_rate arg to u32.. Nothing we can do about that! */
>> + active_rate = min_t(u64, 1000ULL * active_rate, ULONG_MAX);
>> + return clk_set_rate(qp->bus_clk, active_rate);
>> + }
>> +
>> + /* RPM only accepts <=INT_MAX rates */
>> + active_rate = min_t(u32, active_rate, INT_MAX);
>> + sleep_rate = min_t(u32, sleep_rate, INT_MAX);
>
> Realized this by coincidence while playing with the code changes for the
> comment below: This doesn't work as intended similar to the ARM32 cap
> above but it's broken even on ARM64:
>
> Take this example:
>
> u64 active_rate = 4294967296ULL;
> active_rate = min_t(u32, active_rate, INT_MAX);
>
> This should result into active_rate = INT_MAX.
> But it actually results in rate = 0.
>
> Why?
>
> min_t(u32, rate, INT_MAX)
> = min((u32)rate, (u32)INT_MAX)
> = min((u32)4294967296ULL, (u32)INT_MAX)
> = min(0, INT_MAX)
> = 0
>
> This needs to be min_t(u64 to work properly :)
Yikes, right!
>
>> +
>> + if (active_rate != qp->bus_clk_rate[QCOM_SMD_RPM_ACTIVE_STATE]) {
>> + ret = qcom_icc_rpm_set_bus_rate(qp->bus_clk_desc, active_rate, true);
>> + if (ret)
>> return ret;
>> - }
>> - qp->bus_clk_rate[i] = rate;
>> +
>> + /* Cache the rate after we've successfully commited it to RPM */
>> + qp->bus_clk_rate[QCOM_SMD_RPM_ACTIVE_STATE] = active_rate;
>> + }
>> +
>> + if (sleep_rate != qp->bus_clk_rate[QCOM_SMD_RPM_SLEEP_STATE]) {
>> + ret = qcom_icc_rpm_set_bus_rate(qp->bus_clk_desc, sleep_rate, false);
>> + if (ret)
>> + return ret;
>> +
>> + /* Cache the rate after we've successfully commited it to RPM */
>> + qp->bus_clk_rate[QCOM_SMD_RPM_SLEEP_STATE] = sleep_rate;
>> }
>
> With my suggestion on the other patch to pass in the ctx/state number
> directly into qcom_icc_rpm_set_bus_rate() I wonder if it would be nicer
> to write as loop similar to the all others.
>
> It's a bit shorter, although the line wrapping for the keep_alive is
> also more ugly. I leave it up to you :)
>
> Not even compile tested this time!
I think it's more obvious when it's explicit for just two contexts.
Konrad
>
> Thanks,
> Stephan
>
> /*
> * Downstream checks whether the requested rate is zero, but it makes little sense
> * to vote for a value that's below the lower threshold, so let's not do so.
> */
> if (qp->keep_alive)
> agg_clk_rate[QCOM_SMD_RPM_ACTIVE_STATE]
> = max(ICC_BUS_CLK_MIN_RATE, agg_clk_rate[QCOM_SMD_RPM_ACTIVE_STATE]);
>
> /* Some providers have a non-RPM-owned bus clock - convert kHz->Hz for the CCF */
> if (qp->bus_clk) {
> rate = max_t(u64, agg_clk_rate[QCOM_SMD_RPM_ACTIVE_STATE],
> agg_clk_rate[QCOM_SMD_RPM_SLEEP_STATE]);
> /* ARM32 caps clk_set_rate arg to u32.. Nothing we can do about that! */
> reate = min_t(u64, 1000ULL * rate, ULONG_MAX);
> return clk_set_rate(qp->bus_clk, rate);
> }
>
> for (i = 0; i < QCOM_SMD_RPM_STATE_NUM; i++) {
> /* RPM only accepts <=INT_MAX rates */
> rate = min_t(u64, active_rate, INT_MAX);
> if (rate == qp->bus_clk_rate[i])
> continue;
>
> ret = qcom_icc_rpm_set_bus_rate(qp->bus_clk_desc, rate, i);
> if (ret)
> return ret;
>
> /* Cache the rate after we've successfully commited it to RPM */
> qp->bus_clk_rate[i] = rate;
> }
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