From patchwork Thu Jun 1 16:31:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hugo Villeneuve X-Patchwork-Id: 687983 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 AE789C7EE45 for ; Thu, 1 Jun 2023 16:50:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231899AbjFAQuK (ORCPT ); Thu, 1 Jun 2023 12:50:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231439AbjFAQti (ORCPT ); Thu, 1 Jun 2023 12:49:38 -0400 Received: from mail.hugovil.com (mail.hugovil.com [162.243.120.170]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E3D8E53; Thu, 1 Jun 2023 09:49:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=hugovil.com ; s=x; h=Subject:Content-Transfer-Encoding:MIME-Version:References: In-Reply-To:Message-Id:Date:Cc:To:From:Sender:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZiPCnMO76qB2BYRsvuFD+LhH0HMktcgnm3k8GmGktA0=; b=U5b5/XIstKLYENZYR/TX71aRRf yLZ88yJnyKOS44fQJk5ChaDOxrFOnoOecHd+RIThmu1uhGE90VkqltF1RnZYehWDijnkNrRWLTBwZ qGpOii/hQG14HeciG6hJgphqBTP8OWbB8F7RbE4eAzepIOyqyeX4QoBXc04l5NavNfVc=; Received: from modemcable168.174-80-70.mc.videotron.ca ([70.80.174.168]:53588 helo=pettiford.lan) by mail.hugovil.com with esmtpa (Exim 4.92) (envelope-from ) id 1q4lCw-0003BU-P0; Thu, 01 Jun 2023 12:31:27 -0400 From: Hugo Villeneuve To: gregkh@linuxfoundation.org, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, jirislaby@kernel.org, jringle@gridpoint.com, l.perczak@camlintechnologies.com, tomasz.mon@camlingroup.com Cc: linux-serial@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, hugo@hugovil.com, linux-gpio@vger.kernel.org, Hugo Villeneuve , stable@vger.kernel.org, Lech Perczak Date: Thu, 1 Jun 2023 12:31:10 -0400 Message-Id: <20230601163113.2785657-7-hugo@hugovil.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230601163113.2785657-1-hugo@hugovil.com> References: <20230601163113.2785657-1-hugo@hugovil.com> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 70.80.174.168 X-SA-Exim-Mail-From: hugo@hugovil.com Subject: [PATCH v5 6/9] serial: sc16is7xx: fix bug when first setting GPIO direction X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on mail.hugovil.com) Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org From: Hugo Villeneuve When configuring a pin as an output pin with a value of logic 0, we end up as having a value of logic 1 on the output pin. Setting a logic 0 a second time (or more) after that will correctly output a logic 0 on the output pin. By default, all GPIO pins are configured as inputs. When we enter sc16is7xx_gpio_direction_output() for the first time, we first set the desired value in IOSTATE, and then we configure the pin as an output. The datasheet states that writing to IOSTATE register will trigger a transfer of the value to the I/O pin configured as output, so if the pin is configured as an input, nothing will be transferred. Therefore, set the direction first in IODIR, and then set the desired value in IOSTATE. This is what is done in NXP application note AN10587. Fixes: dfeae619d781 ("serial: sc16is7xx") Cc: Signed-off-by: Hugo Villeneuve Reviewed-by: Lech Perczak Tested-by: Lech Perczak --- drivers/tty/serial/sc16is7xx.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c index ad6b9d613b33..2fa09baf28e3 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -1340,9 +1340,18 @@ static int sc16is7xx_gpio_direction_output(struct gpio_chip *chip, state |= BIT(offset); else state &= ~BIT(offset); - sc16is7xx_port_write(port, SC16IS7XX_IOSTATE_REG, state); + + /* + * If we write IOSTATE first, and then IODIR, the output value is not + * transferred to the corresponding I/O pin. + * The datasheet states that each register bit will be transferred to + * the corresponding I/O pin programmed as output when writing to + * IOSTATE. Therefore, configure direction first with IODIR, and then + * set value after with IOSTATE. + */ sc16is7xx_port_update(port, SC16IS7XX_IODIR_REG, BIT(offset), BIT(offset)); + sc16is7xx_port_write(port, SC16IS7XX_IOSTATE_REG, state); return 0; }