PM / Domains: Add support for assigned-performance-states

This is a re-spin of the series that was posted a while back [1] with no major changes except for some review feedback from Stephen addressed.

Back when this was posted, we thought its a good idea if client drivers handle this instead of genpd core handling it [2] So that lead to another series which handled this in the i2c driver [3], but then it looked like it would be duplication of code across drivers and perhaps it should be done some place centrally.

The way forward seems like
1. Get the bindings reviewed from DT folks
2. Once the bindings are finalized, figure out how to handle this centrally without duplication. While this series does it with everything handled in genpd core, there are perhaps other ways to do it with genpd core exporting some helpers and genpd providers handling some of it with callbacks.

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Some devices within power-domains with performance states do not support DVFS, but still need to vote on a default/static state while they are active. Add support for a new device tree property which the clients can use to specify this and add support in kernel to parse this value and vote.

[1] https://lore.kernel.org/patchwork/patch/1284040/
[2] https://lore.kernel.org/patchwork/patch/1284042/
[3] https://lore.kernel.org/patchwork/patch/1356618/

Rajendra Nayak (3):
dt-bindings: power: Introduce 'assigned-performance-states' property PM / Domains: Add support for 'assigned-performance-states'
arm64: dts: sc7180: Add assigned-performance-states for i2c

 .../devicetree/bindings/power/power-domain.yaml    | 50 ++++++++++++++++++++++
 arch/arm64/boot/dts/qcom/sc7180.dtsi               | 24 +++++++++++
 drivers/base/power/domain.c                        | 27 ++++++++++++
 include/linux/pm_domain.h                          |  1 +
 4 files changed, 102 insertions(+)

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