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X-IronPort-AV: E=Sophos;i="5.97,270,1669071600"; d="scan'208";a="28858446" Received: from vtuxmail01.tq-net.de ([10.115.0.20]) by mx1.tq-group.com with ESMTP; 03 Feb 2023 15:20:41 +0100 Received: from steina-w.localnet (unknown [10.123.53.21]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by vtuxmail01.tq-net.de (Postfix) with ESMTPSA id 81E7C280072; Fri, 3 Feb 2023 15:20:41 +0100 (CET) From: Alexander Stein To: Marco Felsch Cc: Jonathan Cameron , Cai Huoqing , Haibo Chen , Lars-Peter Clausen , Rob Herring , Krzysztof Kozlowski , Shawn Guo , Sascha Hauer , Fabio Estevam , devicetree@vger.kernel.org, linux-iio@vger.kernel.org, NXP Linux Team , Pengutronix Kernel Team , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/1] dt-bindings: iio: adc: add missing vref-supply Date: Fri, 03 Feb 2023 15:20:41 +0100 Message-ID: <3214924.aeNJFYEL58@steina-w> Organization: TQ-Systems GmbH In-Reply-To: <20230203141217.et55oxbtxcilg3ig@pengutronix.de> References: <20230131101323.606931-1-alexander.stein@ew.tq-group.com> <1922814.PYKUYFuaPT@steina-w> <20230203141217.et55oxbtxcilg3ig@pengutronix.de> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230203_062045_532871_2785AFB0 X-CRM114-Status: GOOD ( 35.40 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Am Freitag, 3. Februar 2023, 15:12:17 CET schrieb Marco Felsch: > Hi, > > On 23-02-03, Alexander Stein wrote: > > ... > > > > > > > > + vref-supply: > > > > > > > + description: External ADC reference voltage supply on VREFH > > > > > > > pad. > > > > > > > > > > > > Please add it to the list of required properties, we can remove it > > > > > > as > > > > > > soon as the driver has support for the internal reference > > > > > > voltages. > > > > > > > > > > I was thinking in doing so before as well. But DT describes the > > > > > hardware, and this ADC apparently would be functioning without a > > > > > reference voltage on that pad, using a different one. What the > > > > > driver > > > > > actual does is a different matter.> > > > > > > > > I have also thought about it first but than I checked the RM which > > > > says > > > > that "multi-reference selection" is chip dependent. > > > > Nice for pointing this out. I wasn't aware that there are differences. > > > > > Oh goody. So is it detectable? > > > > That's my problem. I didn't find any source of information which chips do > > support multiple references and which don't. > > Marco, do you have some information on this? > > You can download the RM from the NXP website but you need an account for > it: > https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/ > i-mx-applications-processors/i-mx-8-applications-processors/i-mx-8-family-ar > m-cortex-a53-cortex-a72-virtualization-vision-3d-graphics-4k-video:i.MX8 > > Or is this the wrong model? The naming scheme is quite confusing to me. That's i.MX8 (imx8qm), the bindings are for i.MX8X (imx8qxp/imx8dxp). But I assume the ADC is similar/identical. > > > If we are going to stick to a single compatible rather than adding them > > > for > > > the variants with and without this feature, should probably add a note > > > at > > > least to say it is required for some parts. > > > > That's a good idea. I'm okay with that, until there is more information > > available. > > According the RM there is a bit which can be read: Multi Vref > Implemented (MVI). Ah, nice. So there is a hardware feature. From the RM I have available it is set for both imx8qm and imx8qxp. Given that I will not mark this as required, but add a comment regarding this feature bit. Best regards, Alexander > Regards, > Marco _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel