dt-bindings: perf: riscv,pmu: drop unneeded quotes

Drop unneeded quotes over simple string values to fix a soon to be
enabled yamllint warning:

[error] string value is redundantly quoted with any quotes (quoted-strings)

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231122224414.2809184-1-robh@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

dt-bindings: perf: riscv,pmu: fix property dependencies

Seemingly I mis-implemented the dependencies here. The OpenSBI docs only
point out that the "riscv,event-to-mhpmcounters property is mandatory if
riscv,event-to-mhpmevent is present". It never claims that
riscv,event-to-mhpmcounters requires riscv,event-to-mhpmevent.

Drop the dependency of riscv,event-to-mhpmcounters on
riscv,event-to-mhpmevent.

Fixes: 7e38085d9c59 ("dt-bindings: riscv: add SBI PMU event mappings")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20230404-tractor-confusing-8852e552539a@spud
Signed-off-by: Rob Herring <robh@kernel.org>

dt-bindings: riscv: add SBI PMU event mappings

The SBI PMU extension requires a firmware to be aware of the event to
counter/mhpmevent mappings supported by the hardware. OpenSBI may use
DeviceTree to describe the PMU mappings. This binding is currently
described in markdown in OpenSBI (since v1.0 in Dec 2021) & used by QEMU
since v7.2.0.

Import the binding for use while validating dtb dumps from QEMU and
upcoming hardware (eg JH7110 SoC) that will make use of the event
mapping.

Link: https://github.com/riscv-software-src/opensbi/blob/master/docs/pmu_support.md
Link: https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/riscv-sbi.adoc # Performance Monitoring Unit Extension
Co-developed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230113205435.122712-1-conor@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>