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([2a10:a5c0:800d:dd00:8fdf:935a:2c85:d703]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54fc645cee9sm2562141e87.75.2025.05.15.02.19.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 May 2025 02:19:36 -0700 (PDT) Message-ID: <7b23de30-06e3-4f02-a8a5-90791628ceed@gmail.com> Date: Thu, 15 May 2025 12:19:35 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6/9] arm64: dts: imx8mn-bsh-smm-s2-common: Set minimum value for VDD_DRAM_VPU_GPU To: Dario Binacchi , linux-kernel@vger.kernel.org Cc: Simon Holesch , Karthikdatt Anantharamrao , michael@amarulasolutions.com, linux-amarula@amarulasolutions.com, Wolfgang Birkner , Conor Dooley , Fabio Estevam , Krzysztof Kozlowski , Pengutronix Kernel Team , Rob Herring , Sascha Hauer , Shawn Guo , devicetree@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org References: <20250514082507.1983849-1-dario.binacchi@amarulasolutions.com> <20250514082507.1983849-7-dario.binacchi@amarulasolutions.com> Content-Language: en-US, en-AU, en-GB, en-BW From: Matti Vaittinen In-Reply-To: <20250514082507.1983849-7-dario.binacchi@amarulasolutions.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250515_021939_785872_CFC4A46A X-CRM114-Status: GOOD ( 18.91 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 14/05/2025 11:25, Dario Binacchi wrote: > From: Wolfgang Birkner > > Buck3 is called Buck5 in the BD71847 datasheet. This buck supports > 0.55...1.35V. Set the minimum allowed value. Setting this to PMIC's minimum value has little benefits because the voltage can't be set lower than it anyways. AFICS, the idea of the regulator-min-microvolt and the regulator-max-microvolt is to protect a system which can't tolerate lower/higher than NNN voltage. So, basically, these properties are meaningful when PMIC can go higher / lower than the system design tolerates. In these cases the constrains set in device tree should be strictier than the PMIC's range. The existing regulator-min-microvolt = <700000>; could have resulted from the knowledge that the minimum voltage devices connected to the BUCK3 (5 in data-sheet) can survive is 700 mV. Dropping this to 500mV just because PMIC can go there might be plain wrong, and in some case get the device(s) connected to BUCK3/5 upset.. So, please provide better (more) rationale for this change. > > Signed-off-by: Wolfgang Birkner > Signed-off-by: Dario Binacchi > --- > > arch/arm64/boot/dts/freescale/imx8mn-bsh-smm-s2-common.dtsi | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/boot/dts/freescale/imx8mn-bsh-smm-s2-common.dtsi b/arch/arm64/boot/dts/freescale/imx8mn-bsh-smm-s2-common.dtsi > index fd12b97525d1..81fa0a8767e2 100644 > --- a/arch/arm64/boot/dts/freescale/imx8mn-bsh-smm-s2-common.dtsi > +++ b/arch/arm64/boot/dts/freescale/imx8mn-bsh-smm-s2-common.dtsi > @@ -135,7 +135,7 @@ buck2_reg: BUCK2 { > buck3_reg: BUCK3 { > /* PMIC_BUCK5 - VDD_DRAM_VPU_GPU */ > regulator-name = "buck3"; > - regulator-min-microvolt = <700000>; > + regulator-min-microvolt = <550000>; > regulator-max-microvolt = <1350000>; > regulator-boot-on; > regulator-always-on; Yours, -- Matti