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Wed, 15 Apr 2020 03:54:17 -0700 (PDT) Subject: Re: [PATCH V3 7/8] spi: spi-qcom-qspi: Add interconnect support To: Akash Asthana , Mark Brown Cc: gregkh@linuxfoundation.org, agross@kernel.org, bjorn.andersson@linaro.org, wsa@the-dreams.de, mark.rutland@arm.com, robh+dt@kernel.org, linux-i2c@vger.kernel.org, linux-spi@vger.kernel.org, devicetree@vger.kernel.org, swboyd@chromium.org, mgautam@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-serial@vger.kernel.org, mka@chromium.org, dianders@chromium.org, evgreen@chromium.org References: <1585652976-17481-1-git-send-email-akashast@codeaurora.org> <1585652976-17481-8-git-send-email-akashast@codeaurora.org> <20200331112352.GB4802@sirena.org.uk> <20200407105542.GA5247@sirena.org.uk> <48c60fdf-03c6-650a-2671-b8f7cc1e5c82@codeaurora.org> <5644ef02-f984-0f5b-d745-eca3c9573726@linaro.org> From: Georgi Djakov Openpgp: preference=signencrypt Autocrypt: addr=georgi.djakov@linaro.org; prefer-encrypt=mutual; keydata= mQINBFjTuRcBEACyAOVzghvyN19Sa/Nit4LPBWkICi5W20p6bwiZvdjhtuh50H5q4ktyxJtp 1+s8dMSa/j58hAWhrc2SNL3fttOCo+MM1bQWwe8uMBQJP4swgXf5ZUYkSssQlXxGKqBSbWLB uFHOOBTzaQBaNgsdXo+mQ1h8UCgM0zQOmbs2ort8aHnH2i65oLs5/Xgv/Qivde/FcFtvEFaL 0TZ7odM67u+M32VetH5nBVPESmnEDjRBPw/DOPhFBPXtal53ZFiiRr6Bm1qKVu3dOEYXHHDt nF13gB+vBZ6x5pjl02NUEucSHQiuCc2Aaavo6xnuBc3lnd4z/xk6GLBqFP3P/eJ56eJv4d0B 0LLgQ7c1T3fU4/5NDRRCnyk6HJ5+HSxD4KVuluj0jnXW4CKzFkKaTxOp7jE6ZD/9Sh74DM8v etN8uwDjtYsM07I3Szlh/I+iThxe/4zVtUQsvgXjwuoOOBWWc4m4KKg+W4zm8bSCqrd1DUgL f67WiEZgvN7tPXEzi84zT1PiUOM98dOnmREIamSpKOKFereIrKX2IcnZn8jyycE12zMkk+Sc ASMfXhfywB0tXRNmzsywdxQFcJ6jblPNxscnGMh2VlY2rezmqJdcK4G4Lprkc0jOHotV/6oJ mj9h95Ouvbq5TDHx+ERn8uytPygDBR67kNHs18LkvrEex/Z1cQARAQABtChHZW9yZ2kgRGph a292IDxnZW9yZ2kuZGpha292QGxpbmFyby5vcmc+iQI+BBMBAgAoBQJY07kXAhsDBQkHhM4A BgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRCyi/eZcnWWUuvsD/4miikUeAO6fU2Xy3fT l7RUCeb2Uuh1/nxYoE1vtXcow6SyAvIVTD32kHXucJJfYy2zFzptWpvD6Sa0Sc58qe4iLY4j M54ugOYK7XeRKkQHFqqR2T3g/toVG1BOLS2atooXEU+8OFbpLkBXbIdItqJ1M1SEw8YgKmmr JlLAaKMq3hMb5bDQx9erq7PqEKOB/Va0nNu17IL58q+Q5Om7S1x54Oj6LiG/9kNOxQTklOQZ t61oW1Ewjbl325fW0/Lk0QzmfLCrmGXXiedFEMRLCJbVImXVKdIt/Ubk6SAAUrA5dFVNBzm2 L8r+HxJcfDeEpdOZJzuwRyFnH96u1Xz+7X2V26zMU6Wl2+lhvr2Tj7spxjppR+nuFiybQq7k MIwyEF0mb75RLhW33sdGStCZ/nBsXIGAUS7OBj+a5fm47vQKv6ekg60oRTHWysFSJm1mlRyq exhI6GwUo5GM/vE36rIPSJFRRgkt6nynoba/1c4VXxfhok2rkP0x3CApJ5RimbvITTnINY0o CU6f1ng1I0A1UTi2YcLjFq/gmCdOHExT4huywfu1DDf0p1xDyPA1FJaii/gJ32bBP3zK53hM dj5S7miqN7F6ZpvGSGXgahQzkGyYpBR5pda0m0k8drV2IQn+0W8Qwh4XZ6/YdfI81+xyFlXc CJjljqsMCJW6PdgEH7kCDQRY07kXARAAvupGd4Jdd8zRRiF+jMpv6ZGz8L55Di1fl1YRth6m lIxYTLwGf0/p0oDLIRldKswena3fbWh5bbTMkJmRiOQ/hffhPSNSyyh+WQeLY2kzl6geiHxD zbw37e2hd3rWAEfVFEXOLnmenaUeJFyhA3Wd8OLdRMuoV+RaLhNfeHctiEn1YGy2gLCq4VNb 4Wj5hEzABGO7+LZ14hdw3hJIEGKtQC65Jh/vTayGD+qdwedhINnIqslk9tCQ33a+jPrCjXLW X29rcgqigzsLHH7iVHWA9R5Aq7pCy5hSFsl4NBn1uV6UHlyOBUuiHBDVwTIAUnZ4S8EQiwgv WQxEkXEWLM850V+G6R593yZndTr3yydPgYv0xEDACd6GcNLR/x8mawmHKzNmnRJoOh6Rkfw2 fSiVGesGo83+iYq0NZASrXHAjWgtZXO1YwjW9gCQ2jYu9RGuQM8zIPY1VDpQ6wJtjO/KaOLm NehSR2R6tgBJK7XD9it79LdbPKDKoFSqxaAvXwWgXBj0Oz+Y0BqfClnAbxx3kYlSwfPHDFYc R/ppSgnbR5j0Rjz/N6Lua3S42MDhQGoTlVkgAi1btbdV3qpFE6jglJsJUDlqnEnwf03EgjdJ 6KEh0z57lyVcy5F/EUKfTAMZweBnkPo+BF2LBYn3Qd+CS6haZAWaG7vzVJu4W/mPQzsAEQEA AYkCJQQYAQIADwUCWNO5FwIbDAUJB4TOAAAKCRCyi/eZcnWWUhlHD/0VE/2x6lKh2FGP+QHH UTKmiiwtMurYKJsSJlQx0T+j/1f+zYkY3MDX+gXa0d0xb4eFv8WNlEjkcpSPFr+pQ7CiAI33 99kAVMQEip/MwoTYvM9NXSMTpyRJ/asnLeqa0WU6l6Z9mQ41lLzPFBAJ21/ddT4xeBDv0dxM GqaH2C6bSnJkhSfSja9OxBe+F6LIAZgCFzlogbmSWmUdLBg+sh3K6aiBDAdZPUMvGHzHK3fj gHK4GqGCFK76bFrHQYgiBOrcR4GDklj4Gk9osIfdXIAkBvRGw8zg1zzUYwMYk+A6v40gBn00 OOB13qJe9zyKpReWMAhg7BYPBKIm/qSr82aIQc4+FlDX2Ot6T/4tGUDr9MAHaBKFtVyIqXBO xOf0vQEokkUGRKWBE0uA3zFVRfLiT6NUjDQ0vdphTnsdA7h01MliZLQ2lLL2Mt5lsqU+6sup Tfql1omgEpjnFsPsyFebzcKGbdEr6vySGa3Cof+miX06hQXKe99a5+eHNhtZJcMAIO89wZmj 7ayYJIXFqjl/X0KBcCbiAl4vbdBw1bqFnO4zd1lMXKVoa29UHqby4MPbQhjWNVv9kqp8A39+ E9xw890l1xdERkjVKX6IEJu2hf7X3MMl9tOjBK6MvdOUxvh1bNNmXh7OlBL1MpJYY/ydIm3B KEmKjLDvB0pePJkdTw== Message-ID: <1354a27f-217b-c530-c093-d2a5d3df99b2@linaro.org> Date: Wed, 15 Apr 2020 13:54:16 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Hi Akash, On 4/10/20 10:31, Akash Asthana wrote: > Hi Georgi, > > On 4/9/2020 6:47 PM, Georgi Djakov wrote: >> Hi Akash, >> >> On 4/8/20 15:17, Akash Asthana wrote: >>> Hi Mark, Evan, Georgi, >>> >>> On 4/7/2020 4:25 PM, Mark Brown wrote: >>>> On Tue, Apr 07, 2020 at 03:24:42PM +0530, Akash Asthana wrote: >>>>> On 3/31/2020 4:53 PM, Mark Brown wrote: >>>>>>> +    ctrl->avg_bw_cpu = Bps_to_icc(speed_hz); >>>>>>> +    ctrl->peak_bw_cpu = Bps_to_icc(2 * speed_hz); >>>>>> I thought you were going to factor this best guess handling of peak >>>>>> bandwidth out into the core? >>>>> I can centralize this for SPI, I2C and UART  in Common driver(QUP wrapper) >>>>> but still for QSPI I have to keep this piece of code as is because It is not >>>>> child of QUP wrapper(it doesn't use common code). >>>> Why not? >>>> >>>>> I am not sure whether I can move this " Assume peak_bw as twice of avg_bw if >>>>> nothing is mentioned explicitly" to ICC core because the factor of 2 is >>>>> chosen randomly by me. >>>> That's the whole point - if this is just a random number then we may as >>>> well at least be consistently random. >>> Can we centralize below logic of peak_bw selection for all the clients to ICC core? >> I don't think this is a good idea for now, because this is very hardware >> specific. A scaling factor that works for one client might not work for another. >> >> My questions here is how did you decide on this "multiply by two"? I can imagine >> that the traffic can be bursty on some interfaces, but is the factor here really >> a "random number" or is this based on some data patterns or performance >> analysis? > > Factor of 2 is random number. > > We are taking care of actual throughput requirement in avg_bw vote and > the intention of putting peak as twice of avg is to ensure that if high > speed peripherals(ex:USB) removes their votes, we shouldn't see any > latency issue because of other ICC client who don't vote for their BW > requirement or *actual* BW requirement. Thanks for clarifying, but is this latency a confirmed issue on real hardware? I guess voting for twice as average will work, but still wondering wouldn't it be more appropriate to handle it in the interconnect platform driver instead? Also why is the other client not voting, can we fix it? Thanks, Georgi