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[134.60.112.238]) by smtp.gmail.com with ESMTPSA id b124-v6sm5163609wmh.17.2018.09.06.04.39.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Sep 2018 04:39:44 -0700 (PDT) Subject: Re: [PATCH v3 30/30] ARM: sun8i: a83t: full range OPP tables and CPUfreq To: Quentin Schulz Cc: lee.jones@linaro.org, robh+dt@kernel.org, mark.rutland@arm.com, maxime.ripard@bootlin.com, wens@csie.org, linux@armlinux.org.uk, jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, eugen.hristev@microchip.com, rdunlap@infradead.org, vilhelm.gray@gmail.com, clabbe.montjoie@gmail.com, geert+renesas@glider.be, lukas@wunner.de, icenowy@aosc.io, arnd@arndb.de, broonie@kernel.org, arnaud.pouliquen@st.com, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com References: <20180830154518.29507-1-embed3d@gmail.com> <20180830154518.29507-31-embed3d@gmail.com> <20180906072429.7qjwbbqsjlbskk6v@qschulz> From: Philipp Rossak Message-ID: Date: Thu, 6 Sep 2018 13:39:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180906072429.7qjwbbqsjlbskk6v@qschulz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06.09.2018 09:24, Quentin Schulz wrote: > Hi Philipp, > > On Thu, Aug 30, 2018 at 05:45:18PM +0200, Philipp Rossak wrote: >> Since we have now thermal trotteling enabeled we can now add the full >> range of the OPP table. >> > That's not the reason why they were not added. > > Please see commit 2db639d8c1663d7543c9ab5323383d94c8a76c63[1]. > > Basically, you only want the OPPs which can work below or at the default > voltage of the CPU supply, because the CPU supply is specific to each > board. > > If you set your CPU to work at a given frequency and the voltage isn't > updated (saying opp-microvolt = ; in DT isn't enough, you need > cpu-supply to be provided and functional), the CPU might just crash. > > Without cpu-supply property, underclocking isn't effective in term of > thermal cooling or power saving. Overclocking is very, very, very likely > to make the CPU crash. > > It's not a very difficult thing to do to test if a given frequency work > well but it needs a specific test environment and it's a lengthy test, > you can have a look at those tools here[3] if you like. It's not because > it works in a given test case that'll work on the long term under heavy > load and constant frequency changes. > > For A83T, I already did it and the outcome is the patch in [1]. Same for > A33. > > So, if you want to use these three higher OPPs, you need to define them > in your board DTS and add the cpu-supply property. See what's done for > the A33 and more specifically the Sinlinx SinA33[2] as an example. > > [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2db639d8c1663d7543c9ab5323383d94c8a76c63 > [2]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/sun8i-a33-sinlinx-sina33.dts > [3]http://linux-sunxi.org/Hardware_Reliability_Tests#CPU > > Quentin > Hey Quentin, thanks for your feedback! Sounds like we will never be able to run the A83T on its maximum frequency in mainline. I will do some testing, during the next weeks/months when I have time. With the old Allwinner kernel I was able to run the A83T with its maximum frequency without any problems since my board is very good cooled. For now I will drop this patch. Philipp