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Wysocki" , linux-kernel@vger.kernel.org, MyungJoo Ham , Kyungmin Park , Chanwoo Choi , Saravana Kannan Subject: [PATCH v6 0/3] Add required-opps support to devfreq passive gov Date: Thu, 4 Feb 2021 16:14:21 +0800 Message-Id: <20210204081424.2219311-1-hsinyi@chromium.org> X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org The devfreq passive governor scales the frequency of a "child" device based on the current frequency of a "parent" device (not parent/child in the sense of device hierarchy). As of today, the passive governor requires one of the following to work correctly: 1. The parent and child device have the same number of frequencies 2. The child device driver passes a mapping function to translate from parent frequency to child frequency. When (1) is not true, (2) is the only option right now. But often times, all that is required is a simple mapping from parent's frequency to child's frequency. Since OPPs already support pointing to other "required-opps", add support for using that to map from parent device frequency to child device frequency. That way, every child device driver doesn't have to implement a separate mapping function anytime (1) isn't true. Some common (but not comprehensive) reason for needing a devfreq passive governor to adjust the frequency of one device based on another are: 1. These were the combination of frequencies that were validated/screened during the manufacturing process. 2. These are the sensible performance combinations between two devices interacting with each other. So that when one runs fast the other doesn't become the bottleneck. 3. Hardware bugs requiring some kind of frequency ratio between devices. For example, the following mapping can't be captured in DT as it stands today because the parent and child device have different number of OPPs. But with this patch series, this mapping can be captured cleanly. In arch/arm64/boot/dts/exynos/exynos5433-bus.dtsi you have something like this with the following changes: bus_g2d_400: bus0 { compatible = "samsung,exynos-bus"; clocks = <&cmu_top CLK_ACLK_G2D_400>; clock-names = "bus"; operating-points-v2 = <&bus_g2d_400_opp_table>; status = "disabled"; }; bus_noc2: bus9 { compatible = "samsung,exynos-bus"; clocks = <&cmu_mif CLK_ACLK_BUS2_400>; clock-names = "bus"; operating-points-v2 = <&bus_noc2_opp_table>; status = "disabled"; }; bus_g2d_400_opp_table: opp_table2 { compatible = "operating-points-v2"; opp-shared; opp-400000000 { opp-hz = /bits/ 64 <400000000>; opp-microvolt = <1075000>; required-opps = <&noc2_400>; }; opp-267000000 { opp-hz = /bits/ 64 <267000000>; opp-microvolt = <1000000>; required-opps = <&noc2_200>; }; opp-200000000 { opp-hz = /bits/ 64 <200000000>; opp-microvolt = <975000>; required-opps = <&noc2_200>; }; opp-160000000 { opp-hz = /bits/ 64 <160000000>; opp-microvolt = <962500>; required-opps = <&noc2_134>; }; opp-134000000 { opp-hz = /bits/ 64 <134000000>; opp-microvolt = <950000>; required-opps = <&noc2_134>; }; opp-100000000 { opp-hz = /bits/ 64 <100000000>; opp-microvolt = <937500>; required-opps = <&noc2_100>; }; }; bus_noc2_opp_table: opp_table6 { compatible = "operating-points-v2"; noc2_400: opp-400000000 { opp-hz = /bits/ 64 <400000000>; }; noc2_200: opp-200000000 { opp-hz = /bits/ 64 <200000000>; }; noc2_134: opp-134000000 { opp-hz = /bits/ 64 <134000000>; }; noc2_100: opp-100000000 { opp-hz = /bits/ 64 <100000000>; }; }; -Saravana v5 -> v6: - fix review comments v4 -> v5: - drop patch "OPP: Improve required-opps linking" and rebase to https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm.git/log/?h=opp/linux-next - Compare pointers in dev_pm_opp_xlate_required_opp(). v3 -> v4: - Fixed documentation comments - Fixed order of functions in .h file - Renamed the new xlate API - Caused _set_required_opps() to fail if all required opps tables aren't linked. v2 -> v3: - Rebased onto linux-next. - Added documentation comment for new fields. - Added support for lazy required-opps linking. - Updated Ack/Reviewed-bys. v1 -> v2: - Cached OPP table reference in devfreq to avoid looking up every time. - Renamed variable in passive governor to be more intuitive. - Updated cover letter with examples. Saravana Kannan (3): OPP: Add function to look up required OPP's for a given OPP PM / devfreq: Cache OPP table reference in devfreq PM / devfreq: Add required OPPs support to passive governor drivers/devfreq/devfreq.c | 6 +++ drivers/devfreq/governor_passive.c | 25 +++++++++---- drivers/opp/core.c | 59 ++++++++++++++++++++++++++++++ include/linux/devfreq.h | 2 + include/linux/pm_opp.h | 7 ++++ 5 files changed, 92 insertions(+), 7 deletions(-)