From patchwork Mon Mar 16 20:27:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jacopo Mondi X-Patchwork-Id: 210599 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 208E8C4CECE for ; Mon, 16 Mar 2020 20:25:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0152320658 for ; Mon, 16 Mar 2020 20:25:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732566AbgCPUZW (ORCPT ); Mon, 16 Mar 2020 16:25:22 -0400 Received: from relay9-d.mail.gandi.net ([217.70.183.199]:54871 "EHLO relay9-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732556AbgCPUZW (ORCPT ); Mon, 16 Mar 2020 16:25:22 -0400 X-Originating-IP: 2.224.242.101 Received: from uno.localdomain (2-224-242-101.ip172.fastwebnet.it [2.224.242.101]) (Authenticated sender: jacopo@jmondi.org) by relay9-d.mail.gandi.net (Postfix) with ESMTPSA id 5729EFF803; Mon, 16 Mar 2020 20:25:19 +0000 (UTC) From: Jacopo Mondi To: kieran.bingham+renesas@ideasonboard.com, niklas.soderlund@ragnatech.se, laurent.pinchart@ideasonboard.com Cc: Jacopo Mondi , hyunk@xilinx.com, manivannan.sadhasivam@linaro.org, linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org Subject: [PATCH 4/5] dt-bindings: media: max9286: Add reverse channel amplitude Date: Mon, 16 Mar 2020 21:27:56 +0100 Message-Id: <20200316202757.529740-5-jacopo+renesas@jmondi.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200316202757.529740-1-jacopo+renesas@jmondi.org> References: <20200316202757.529740-1-jacopo+renesas@jmondi.org> MIME-Version: 1.0 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org The MAX9286 chip exposes registers to control the reverse channel amplitude signal. The channel amplitude has to be configured according to the connected remote serializer settings, in order to guarantee reliable communications. Serializer might be pre-programmed and initialize with their reverse channel noise threshold level increased. While this is intended to increase the signal/noise immunity ratio on the channel, the deserializer should be initialized accordingly, with its channel amplitude increased to 170mV. Add to the bindings documentation a required property to allow DTS users to specify the initial setting of the deserializer reverse channel and accommodate different serializer models. Signed-off-by: Jacopo Mondi --- .../bindings/media/i2c/maxim,max9286.yaml | 21 +++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml index ee8e0418b3f0..a1c56734a727 100644 --- a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml @@ -54,6 +54,25 @@ properties: allOf: - $ref: /schemas/types.yaml#/definitions/uint32 + maxim,reverse-channel-amplitude: + description: | + The reverse channel amplitude initial value, in milliVolts. If the remote + serializer is pre-programmed with an high reverse channel noise threshold, + the deserializer channel amplitude shall initially be increased to 170mV + to allow the two to communicate reliably. Likewise, if the remote + serializer probes without an increased reverse channel noise threshold, + the deserializer initial reverse channel amplitude should be set to 100mV + to be later increased to 170mV after serializers have increased their + reverse channel noise threshold. + maxItems: 1 + allOf: + - $ref: /schemas/types.yaml#/definitions/uint32 + # The property can be easily expanded to support more values if needed, + # but that's what's supported today by the driver. + oneOf: + - const: 100 + - const: 170 + ports: type: object description: | @@ -155,6 +174,7 @@ required: - compatible - reg - maxim,overlap-window + - maxim,reverse-channel-amplitude - ports - i2c-mux @@ -177,6 +197,7 @@ examples: poc-supply = <&camera_poc_12v>; enable-gpios = <&gpio 13 GPIO_ACTIVE_HIGH>; maxim,overlap-window = MAX9286_OVLP_WINDOW_DISABLED; + maxim,reverse-channel-amplitude = <170>; ports { #address-cells = <1>;