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Thu, 02 Oct 2025 13:43:45 -0700 (PDT) Message-ID: <30efd90b-ba9f-4291-b9a1-8739f1c5f24b@gmail.com> Date: Thu, 2 Oct 2025 13:42:20 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/11] Linux RISC-V trace framework and drivers To: Greg KH , Anup Patel Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Paul Walmsley , Palmer Dabbelt , Alexander Shishkin , Ian Rogers , Alexandre Ghiti , Peter Zijlstra , Ingo Molnar , Namhyung Kim , Mark Rutland , Jiri Olsa , Adrian Hunter , Liang Kan , Mayuresh Chitale , Anup Patel , Atish Patra , Andrew Jones , Sunil V L , linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251002060732.100213-1-apatel@ventanamicro.com> <2025100208-challenge-protrude-d6c3@gregkh> <2025100255-catcall-drinkable-23f5@gregkh> Content-Language: en-US From: Bo Gan In-Reply-To: <2025100255-catcall-drinkable-23f5@gregkh> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/1/25 23:44, Greg KH wrote: > On Thu, Oct 02, 2025 at 12:09:23PM +0530, Anup Patel wrote: >> On Thu, Oct 2, 2025 at 11:56 AM Greg KH wrote: >>> >>> On Thu, Oct 02, 2025 at 11:37:21AM +0530, Anup Patel wrote: >>>> This series adds initial support for RISC-V trace framework and drivers. >>>> The RISC-V trace v1.0 specification is already ratified and can be found at: >>>> https://github.com/riscv-non-isa/e-trace-encap/releases/tag/v1.0.0-ratified >>>> https://github.com/riscv-non-isa/tg-nexus-trace/releases/tag/1.0_Ratified >>>> >>>> The RISC-V trace framework and drivers are designed to be agnostic to the >>>> underlying trace protocol hence both RISC-V E-trace and RISC-V N-trace should >>>> work fine. The discovery of trace protocl parameters are left to user-space >>>> trace decoder. >>>> >>>> In ther future, there will be subsequent series adding: >>>> 1) Sysfs support >>> >>> why does "trace" need sysfs support? No other cpu platform uses that >>> today, so why is a new user/kernel api needed? >> >> We saw trace support for other architectures (e.g. ARM coresight) allowing >> trace start/stop through sysfs. If this is an obsolete or not preferred approach >> then we will deprioritize and possibly never add it. > > Why is that needed for coresight and other arches do not need it? > Perhaps it should be deleted from that codebase instead? > > thanks, > > greg k-h Hi Greg, sysfs is helpful for controlling the trace if not utilized through perf framework. It can also be used by userspace to discover the topology of trace components and their capabilities. @Anup I assume this driver is designed with other sinks in mind (not just ramsink), so it can be used to emit trace to external probes, right? Bo