linux-kernel - [RFC PATCH 0/6] Support raw event and DT for perf on RISC-V

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Message-Id: <cover.1593397455.git.zong.li@sifive.com>
Date:   Mon, 29 Jun 2020 11:19:09 +0800
From:   Zong Li <zong.li@...ive.com>
To:     palmer@...belt.com, paul.walmsley@...ive.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Zong Li <zong.li@...ive.com>
Subject: [RFC PATCH 0/6] Support raw event and DT for perf on RISC-V

This patch set adds raw event support on RISC-V. In addition, we
introduce the DT mechanism to make our perf more generic and common.

Currently, we set the hardware events by writing the mhpmeventN CSRs, it
would raise an illegal instruction exception and trap into m-mode to
emulate event selector CSRs access. It doesn't make sense because we
shouldn't write the m-mode CSRs in s-mode. Ideally, we should set event
selector through standard SBI call or the shadow CSRs of s-mode. We have
prepared a proposal of a new SBI extension, called "PMU SBI extension",
but we also discussing the feasibility of accessing these PMU CSRs on
s-mode at the same time, such as delegation mechanism, so I was
wondering if we could use SBI calls first and make the PMU SBI extension
as legacy when s-mode access mechanism is accepted by Foundation? or
keep the current situation to see what would happen in the future.

This patch set also introduces the DT mechanism, we don't want to add too
much platform-dependency code in perf like other architectures, so we
put the mapping of generic hardware events to DT, then we can easy to
transfer generic hardware events to vendor's own hardware events without
any platfrom-dependency stuff in our perf.

Zong Li (6):
  dt-bindings: riscv: Add YAML documentation for PMU
  riscv: dts: sifive: Add DT support for PMU
  riscv: add definition of hpmcounter CSRs
  riscv: perf: Add raw event support
  riscv: perf: introduce DT mechanism
  riscv: remove PMU menu of Kconfig

 .../devicetree/bindings/riscv/pmu.yaml        |  59 +++
 arch/riscv/Kconfig                            |  13 -
 arch/riscv/boot/dts/sifive/fu540-c000.dtsi    |  13 +
 arch/riscv/include/asm/csr.h                  |  58 +++
 arch/riscv/include/asm/perf_event.h           | 100 ++--
 arch/riscv/kernel/Makefile                    |   2 +-
 arch/riscv/kernel/perf_event.c                | 471 +++++++++++-------
 7 files changed, 471 insertions(+), 245 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/riscv/pmu.yaml

-- 
2.27.0