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([2a01:e0a:982:cbb0:94c3:7db:6fa6:5605]) by smtp.gmail.com with ESMTPSA id n4-20020a7bcbc4000000b003dc3f3d77e3sm8873890wmi.7.2023.02.27.06.46.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Feb 2023 06:46:52 -0800 (PST) Message-ID: <13cf3223-d3fb-1a3e-f13a-77db3b6d144c@linaro.org> Date: Mon, 27 Feb 2023 15:46:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.2 From: neil.armstrong@linaro.org Subject: Re: [PATCH v1 0/3] Meson A1 32-bit support To: Dmitry Rokosov , arm@kernel.org, soc@kernel.org Cc: Alexey Romanov , robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, khilman@baylibre.com, jbrunet@baylibre.com, martin.blumenstingl@googlemail.com, linus.walleij@linaro.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru References: <20230222115020.55867-1-avromanov@sberdevices.ru> <8e5f9bfa-d612-cd43-d722-d04c40938c62@linaro.org> <20230227142809.kujmrraf3pcdhqyn@CAB-WSD-L081021> Content-Language: en-US Organization: Linaro Developer Services In-Reply-To: <20230227142809.kujmrraf3pcdhqyn@CAB-WSD-L081021> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230227_064655_918267_2BE6C90F X-CRM114-Status: GOOD ( 22.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: neil.armstrong@linaro.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 27/02/2023 15:28, Dmitry Rokosov wrote: > Hello Neil! > > On Mon, Feb 27, 2023 at 09:15:04AM +0100, neil.armstrong@linaro.org wrote: > > [...] > >> I'm aware Amlogic also runs their kernel as 32bit to gain a few kbytes >> of memory, but those processors are ARMv8 and the arm64 arch code >> has been designed for those CPUs. >> >> So far I didn't find a single good reason to add 32bit support for >> ARMv8 Amlogic based SoCs, if you have a solid reason please share. > > I totally agree with you, but I suppose it's fully related to 'big' > Amlogic SoC like S905_ or A311_ series. A113L (aka 'a1') is > a cost-efficient dual-core SoC which is used for small, cheap solutions > with cheap components. Every cent is important during BoM development. > That's why usually ODMs install small ROM and RAM capacity, and each > megabyte is important for RAM/ROM kernel and rootfs footprints. Do you have figures ? is 32bit ARM kernel really lighter when ARM64 one is correctly configured ? > Why am I talking about rootfs? For such small projects a good > choice is buildroot rootfs assembling framework. Unfortunatelly, > buildroot doesn't support 'compat' mode when kernel and userspace have > a different bitness. well this is a buildroot problem... the kernel itself is perfectly capable of running an AArch32 userspace. > In the internal project, we save several > percents of ROM/RAM free space using 32-bit configuration (mostly rootfs > ROM space, to be honest). Therefore, for such 'little' cost-efficient > SoCs we can make an exception and support 32-bit configuration, from my > point of view. 32bit ARM is now "legacy", I would need to have an advice from the ARM SoC maintainers, but AFAIK new ARMv8 SoCs should stay in arm64 arch. Arnd ? Olof ? do you have an opinion on this ? > > What do you think about that? >> >> And as Krzysztof stated, the support is incomplete and cannot work >> without a dts file. > > Agreed, we shouldn't merge dead code. But there are several question to > discuss there. Please check my reply to Krzysztof message. > > [...] > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel