Messages in this thread | | | Subject | Re: [PATCH v4 0/5] Add required-opps support to devfreq passive gov | From | Chanwoo Choi <> | Date | Thu, 14 Nov 2019 16:54:21 +0900 |
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Dear Saravana,
Any other progress of this series?
Regards, Chanwoo Choi
On 7/24/19 10:42 AM, Saravana Kannan wrote: > 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 > > 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 (5): > OPP: Allow required-opps even if the device doesn't have power-domains > OPP: Add function to look up required OPP's for a given OPP > OPP: Improve required-opps linking > 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 | 20 ++++-- > drivers/opp/core.c | 83 +++++++++++++++++++--- > drivers/opp/of.c | 108 ++++++++++++++--------------- > drivers/opp/opp.h | 5 ++ > include/linux/devfreq.h | 2 + > include/linux/pm_opp.h | 11 +++ > 7 files changed, 165 insertions(+), 70 deletions(-) >
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