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Fri, 20 Dec 2019 08:24:06 -0800 (PST) Received: from [10.28.17.247] ([192.19.231.250]) by smtp.gmail.com with ESMTPSA id d14sm10896103wru.9.2019.12.20.08.24.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Dec 2019 08:24:05 -0800 (PST) Subject: Re: [PATCH 1/2] include: trace: Add SCMI header with trace events To: Lukasz Luba , Sudeep Holla Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, rostedt@goodmis.org References: <20191216161650.21844-1-lukasz.luba@arm.com> <20191218120900.GA28599@bogus> <7b59a2f1-0786-d24f-a653-76a60c15a8ae@broadcom.com> <7fe599d3-1ce2-1fde-2911-9516a26090b6@arm.com> From: Jim Quinlan Openpgp: preference=signencrypt Autocrypt: addr=james.quinlan@broadcom.com; prefer-encrypt=mutual; keydata= mQENBFOXa3ABCADHz9QNP8upEMOGzf0RJ1lhBRnacq5Gz9fcbmcxK2y4PXtT1JR2WJWT3roY oHUXKL42zA74Iv6ODOjvO/VcvmJTllbz5zhuj5hDHBTNdSdspHWJMS3VdRtB5YQ4+4SNfi4O +ucstwf5U8HHLtsFes1udLWgujK4CD2mHBpR1tIc7dXP7jsCcxvkwA/jMN8D8w80kE1RY1eM 3Chfft2oJOMK54n8f9x+iWdDsXV2e5vk0TLAJPB8ErGbAWj+HF+SQ/QdI6hdn/KbEQgJyZCV t8mB2uDfjvp14PIY02OSu9vgEWVYMMPoNLazromChJBtflewbp/Uim7BWYvcYRCPwx7VABEB AAG0KEppbSBRdWlubGFuIDxqYW1lcy5xdWlubGFuQGJyb2FkY29tLmNvbT6JATgEEwECACIF AlazUjUCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJENnFxA/a7tJZiMwH/RHLgTPx BzrlFPQbEDfh05FXthTM0r1wC8AwHGmXhaxMT352Ju4jqCPvhF4YbczqEmuSFqOHZ6hQhBah L/O4QYRtBUCYhGg/cQ5WzklE48A2iNEoSsA8rP6Cy4wzXKrO0yPHQPyDtQ/o/Fa6T6r2EBAT mVtQBizeiDkUKDgfYU+o0iTW+205myQ9tTe3R0BJmq+F6dYdusKHRn9QXkm5oUC/tea3bq6N jnExBVz8LFaZRxe5uVs5Hwa+ZZqqsj3xJ6CmPQIktjcX8cHUSdrd/B7BC/kBwhhUeKT5HfQl KNk75rbMY8vJy8emev72Tyi3zq3tNy7DZvZoAmX5NGua8625AQ0EU5drcAEIAKmzln4+BvCz CfrbQqCd/EUhmVesujmNO2lTUFL20Wv1Kq27ZFXPaWfe9+lxg9R+p1Ry4ChRk7xZ34r56t0i lGZKH2CIETGChBedfOoDTcgt7K9lMlIxl9QIVEt5yxaqUExN38TIeEayBdeZSbPtmWzGQGl1 kaUHY8l8GWSVB6mJrJaEnfpxt8xTbHdCbPzRM2nf5w76IFFvIP6ojnW06fWYTSYisPuidZs/ 7r1s8GpucrveKXNpzw3li9ChzI90zTBpMl3jWtqOQE5Nn0UHpPvN2SiAJ/Gm18LRP8TCTmOU bpLN2UoJhUGdscyYen+ECxVEZXsQCyASJvGzcWHjQL8AEQEAAYkBHwQYAQIACQUCU5drcAIb DAAKCRDZxcQP2u7SWUnTCAC8GirJT3daWnIgc23Qw0caHxP9dHLNKf4Fo1bxss5n6JoZgQWt kvqWRBBGqHTBbVBrScH5jI7kYRXaP37Q6J4bOxi68L/NC9qY7y41M6O+EaRZ4xYR5PjXY7yu eEeLGk0U8L6lgOtCH53lhk0i4E5BRKvg71T0UvmJPpSmtYUo/JH0sCinJADCQx+C961yPerJ xOO2mNvMpvXjMSqeWzYmZ9uhvRGVfo5O9i4MdFXpSm/3a3i/bZLaxPt3tjxJu+aPKHHadKcr 8EmSDiRrCGBbnhED/fvI/titv3qxtMBLAY++03FOh6XC93NjsRC3yCogAY7iIuWoWBmisCQ6 Kcyg Message-ID: <9befbc13-ba00-094d-0064-0d97c1ccbb63@broadcom.com> Date: Fri, 20 Dec 2019 11:24:03 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <7fe599d3-1ce2-1fde-2911-9516a26090b6@arm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Thank you for sharing your experiments and thoughts. I have probably > similar setup for stressing the communication channel, but I do also > some wired things in the firmware. That's why I need to measure these > delays. I am happy that it is useful for you also. > > I don't know if your firmware supports 'fast channel', but please keep > in mind that it is not tracked in this 'transfer_id'. > This transfer_id in v2 version does not show the real transfers > to the firmware since there is another path called 'fast channel' or > 'fast_switch' in the CPUfreq. It is in drivers/firmware/arm_scmi/perf.c= > and the atomic variable is not incremented in that path. Adding it also= > there just for atomic_inc() probably would add delays in the fast_switc= h > and also brings little value. > For the normal channel, where we have spinlocks and other stuff, this > atomic_inc() could stay in my opinion. > > Regards, > Lukasz Hi Lukasz, We currently do not use "fast channels" - although it is possible we migh= t someday. I find the transfer_id useful per your v2 even if it doesn't cover FC.=C2= =A0 Thanks for submitting and discussing this! Regards, Jim Quinlan