From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6118CC4332F for ; Mon, 6 Nov 2023 14:25:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231770AbjKFOZ1 (ORCPT ); Mon, 6 Nov 2023 09:25:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231358AbjKFOZZ (ORCPT ); Mon, 6 Nov 2023 09:25:25 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD4A9C6; Mon, 6 Nov 2023 06:25:22 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 77C91C433C8; Mon, 6 Nov 2023 14:25:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699280722; bh=HY3kSLldl7rK8Qt1R1njkwITH3UB/c7/iTo+eGw2/5g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dfuahSDA/ik+wqTm44m7fP26rdFTxfGHXXZAKtyCwwZL+BxZTfimvszIss7cGXVMK kta0oN61FDmSKiy356qtTiM36ZO08ms5xIsA/Wdu3q5PiG+VeFI5HGGD0BrCdwv3ry Uiw0Q1gnPy4/4MXy6Y0Zr4iTtshf0OMxdXWVrTvc3zYo3pNLPnO8MTS5H+l0yZfAn0 CVi2wIg/VJ8PGrZMoBZ4SVGP1lC1Rf1cli4TI36cIxzjPv6MaPFEgtZSyEd/aV3gR3 JBvEwolJGEI4j3CM3NHHGz7cQt5ObIFJSE0aHoePGuSNLHbPOj3J0pXIuu2eEt/nhK 0+dPGI19MJMfw== Received: from johan by xi.lan with local (Exim 4.96) (envelope-from ) id 1r00YJ-0000Ob-2S; Mon, 06 Nov 2023 15:26:08 +0100 Date: Mon, 6 Nov 2023 15:26:07 +0100 From: Johan Hovold To: Wolfram Sang Cc: linux-renesas-soc@vger.kernel.org, Geert Uytterhoeven , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 3/3] gnss: ubx: add support for the reset gpio Message-ID: References: <20231103225601.6499-1-wsa+renesas@sang-engineering.com> <20231103225601.6499-4-wsa+renesas@sang-engineering.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231103225601.6499-4-wsa+renesas@sang-engineering.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 03, 2023 at 11:56:00PM +0100, Wolfram Sang wrote: > The Renesas KingFisher board includes a U-Blox Neo-M8 chip. This chip > has a reset pin which is also wired on the board. Add code to the driver > to support this reset pin. Because my GNSS device is hooked up via UART > and I2C simultaneously, I could verify functionality by opening/closing > the GNSS device using UART and see if the corresponding I2C device was > visible on the bus. > static int ubx_set_active(struct gnss_serial *gserial) > @@ -29,6 +31,8 @@ static int ubx_set_active(struct gnss_serial *gserial) > if (ret) > return ret; > > + gpiod_set_value_cansleep(data->reset_gpio, 0); > + > return 0; > } > > @@ -37,6 +41,8 @@ static int ubx_set_standby(struct gnss_serial *gserial) > struct ubx_data *data = gnss_serial_get_drvdata(gserial); > int ret; > > + gpiod_set_value_cansleep(data->reset_gpio, 1); > + > ret = regulator_disable(data->vcc); > if (ret) > return ret; > @@ -90,6 +96,13 @@ static int ubx_probe(struct serdev_device *serdev) > if (ret < 0 && ret != -ENODEV) > goto err_free_gserial; > > + /* Start with reset asserted */ > + data->reset_gpio = devm_gpiod_get_optional(&serdev->dev, "reset", GPIOD_OUT_HIGH); > + if (IS_ERR(data->reset_gpio)) { > + ret = PTR_ERR(data->reset_gpio); > + goto err_free_gserial; > + } > + > ret = gnss_serial_register(gserial); > if (ret) > goto err_free_gserial; So as I just replied to you v3, the hardware integration manual for NEO-M8 and the datasheets for some of the other modules explicitly says that the RESET_N pin should not be used this way: 1.5 I/O pins RESET_N: Reset input Driving RESET_N low activates a hardware reset of the system. Use this pin only to reset the module. Do not use RESET_N to turn the module on and off, since the reset state increases power consumption. (and AFAIU you should generally not try to use reset this way unless it is explicitly said to be supported). Johan