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[1.160.164.133]) by smtp.gmail.com with ESMTPSA id q16-20020a170902dad000b00199193e5ea1sm3286293plx.61.2023.03.18.06.17.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Mar 2023 06:17:43 -0700 (PDT) Message-ID: <7cc8258c-3a77-5387-aaa4-658761fbb0ae@gmail.com> Date: Sat, 18 Mar 2023 21:17:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH 11/15] arm64: dts: nuvoton: Add initial ma35d1 device tree To: Arnd Bergmann , Rob Herring , krzysztof.kozlowski+dt@linaro.org, Lee Jones , Michael Turquette , Stephen Boyd , Philipp Zabel , Greg Kroah-Hartman , Jiri Slaby Cc: devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, schung@nuvoton.com, Jacky Huang References: <20230315072902.9298-1-ychuang570808@gmail.com> <20230315072902.9298-12-ychuang570808@gmail.com> <2063c6d1-85ed-43d9-b572-a762b6ce18c1@app.fastmail.com> Content-Language: en-US From: Jacky Huang In-Reply-To: <2063c6d1-85ed-43d9-b572-a762b6ce18c1@app.fastmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dear Arnd, Thanks for your suggestion. On 2023/3/16 下午 10:17, Arnd Bergmann wrote: > On Wed, Mar 15, 2023, at 08:28, Jacky Huang wrote: >> + mem: memory@80000000 { >> + device_type = "memory"; >> + reg = <0x00000000 0x80000000 0 0x20000000>; /* 512M DRAM */ >> + }; >> +}; > In most machines, the memory size is detected by the boot loader > and filled in the dtb in memory before starting the kernel, so > you should not need two separate files here for the two common > memory configurations. On ma35d1, memory size is determined early before uboot. BL1 (MaskROM boot code) -> BL2 (arm-trust-firmware) -> BL32 (op-tee) & BL33 (uboot). The DDR was initialized in BL2 stage with a selected DDR setting, which is hard coded, including DDR size. We searched the arm64 dts and found that almost all vendors claimed memory size in board level dtsi/dts. This seems to be common. So, can we have it unchanged? > Since the machine is called 'som', I would assume that this is a > module that is integrated on another board, so more commonly one > would have a dtsi file for the som in addition to the one for the > soc, and have all the components of the module listed in this > file, while the dts file that includes the som.dtsi lists the > devices on the carrier board and enables the on-chip devices > that are connected to the outside. > > Arnd You are right, ma35d1 som have a base board, and a cpu board on it. It is a good suggestion that we should have a dtsi for som base board. Consider that we are in the initial submit, and such a dtsi will be an empty file at this stage. So, I would like to do it when peripheral drivers upstream started. Is it ok? Best  regards, Jacky Huang