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Message-ID: <ZIeGGn7emge6Xkb0@gerhold.net>
Date: Mon, 12 Jun 2023 22:54:50 +0200
From: Stephan Gerhold <stephan@...hold.net>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
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 v3 18/23] interconnect: qcom: icc-rpm: Control bus rpmcc
from icc
On Mon, Jun 12, 2023 at 08:24:35PM +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, but that's a mistake in and of itself).
>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
Would be nice to add a comment here already that you're breaking
compatbility with the qcom,icc.h. It's a bit hidden otherwise.
> ---
> drivers/interconnect/qcom/icc-rpm.c | 114 ++++++++++++++++++++----------------
> drivers/interconnect/qcom/icc-rpm.h | 13 ++--
> drivers/interconnect/qcom/msm8996.c | 1 -
> drivers/interconnect/qcom/sdm660.c | 1 -
> 4 files changed, 66 insertions(+), 63 deletions(-)
>
> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
> index b8ecf9538ab9..5ffcf5ca8914 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 +363,54 @@ 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);
> +
> + if ((active_rate != qp->bus_clk_rate[QCOM_SMD_RPM_ACTIVE_STATE]) ||
> + (sleep_rate != qp->bus_clk_rate[QCOM_SMD_RPM_SLEEP_STATE])) {
> + ret = qcom_icc_rpm_set_bus_rate(qp->bus_clk_desc,
> + active_rate,
> + sleep_rate);
> + if (ret)
> return ret;
Hm, do we have to set both rates together in all cases? If cpufreq is
quickly changing frequencies (and therefore active-only ICC bandwidths)
it should be sufficient to make one call into RPM and leave the sleep
rate as-is. Especially because you already cache the two rates
separately.
AFAICT downstream updates the contexts completely separately, so I don't
think it updates both rates at once either. And actually even the old
code before this patch didn't do that :D
Thanks,
Stephan
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