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([2a02:8010:6606:0:1cb3:1c74:2f0b:e9ac]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477184e4006sm2064515e9.5.2025.10.27.12.08.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Oct 2025 12:08:55 -0700 (PDT) Message-ID: Date: Mon, 27 Oct 2025 19:08:53 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: dts: rockchip: pwm-fan overlay for NanoPC-T6 To: Alexey Charkov Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Heiko Stuebner , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org References: <20251026194858.92461-1-sigmaris@gmail.com> Content-Language: en-GB From: Hugh Cole-Baker In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 27/10/2025 09:14, Alexey Charkov wrote: > Hi Hugh, > > On Mon, Oct 27, 2025 at 1:09 PM Hugh Cole-Baker wrote: >> >> FriendlyELEC offers an optional heatsink and fan addon for the NanoPC-T6 >> and T6 LTS. Add an overlay which can be applied if the fan is fitted and >> configures the fan as an active cooling device for the SoC package. >> >> Signed-off-by: Hugh Cole-Baker >> --- >> FriendlyELEC heatsink with fan addon: >> https://www.friendlyelec.com/index.php?route=product/product&product_id=305 >> Vendor DT with trip points and PWM duty cycle values: >> https://github.com/friendlyarm/kernel-rockchip/blob/4944602540b62f5aad139fe602a76cf7c3176128/arch/arm64/boot/dts/rockchip/rk3588-nanopi6-rev01.dts#L75-L90 Hi Alexey, > Is there any downside to enabling this unconditionally in the board > .dts? Only that it goes against the principle that the DT should describe the hardware; the board .dts would describe a cooling device that doesn't actually exist on the base board. I guess then in theory, an OS might allow the SoC to reach undesirably high temperatures if it's relying on the nonexistent fan to cool it down. But I don't think this would be an issue on Linux, at least, in practice. > Overlays require more user configuration, and not all > bootloaders support them directly (e.g. systemd-boot users would > struggle). Compiling with overlays enabled also makes .dtb's a lot > larger due to added symbols information. Nowadays (on Debian at least) using overlays is pretty easy, I'm using the u-boot-menu package in Debian, I just copy the overlay(s) to /boot/dtbo/ and it detects them automatically and adds them to extlinux.conf for u-boot to apply. Couldn't systemd-boot users just use rk3588-nanopc-t6-(lts-)with-fan.dtb as their single DT to load, if it doesn't support applying overlays and they want to use the fan addon? FWIW, I haven't noticed any problems with having a larger .dtb (using mainline U-Boot to load it) and several other RK3588 boards are also compiled with symbols enabled already, and I haven't seen any issues reported with them. Best regards, Hugh