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 AEB4CC433F5 for ; Mon, 14 Mar 2022 11:41:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239528AbiCNLmN (ORCPT ); Mon, 14 Mar 2022 07:42:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239521AbiCNLl5 (ORCPT ); Mon, 14 Mar 2022 07:41:57 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 41FAF49CA8; Mon, 14 Mar 2022 04:39:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0B12BB80DB9; Mon, 14 Mar 2022 11:39:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 188ABC340EC; Mon, 14 Mar 2022 11:39:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1647257961; bh=mwnCZ0OQrFjkyrpo4OL0dRkI5nNOtDz6vfSYkzZWJPo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cLyjx97cCbTrEzRIQiGX/0JeRpA+rvOHvhQW+KxJDDR64IeYhlyx3bPrZiJwGahP1 sHQVeZ3RXjeXEVWFo7Iw9yVBVXU7tji1Vw6bRVEAAE7CkBc/pOcNR3wukQjGacKpbO 46vuF3MgKC7SBGi9aGcaNX5EPoTJ8egwzXcCKius= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mark Featherston , Kris Bahnsen , Bartosz Golaszewski , Sasha Levin Subject: [PATCH 4.19 09/30] gpio: ts4900: Do not set DAT and OE together Date: Mon, 14 Mar 2022 12:34:27 +0100 Message-Id: <20220314112732.050836462@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220314112731.785042288@linuxfoundation.org> References: <20220314112731.785042288@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Mark Featherston [ Upstream commit 03fe003547975680fdb9ff5ab0e41cb68276c4f2 ] This works around an issue with the hardware where both OE and DAT are exposed in the same register. If both are updated simultaneously, the harware makes no guarantees that OE or DAT will actually change in any given order and may result in a glitch of a few ns on a GPIO pin when changing direction and value in a single write. Setting direction to input now only affects OE bit. Setting direction to output updates DAT first, then OE. Fixes: 9c6686322d74 ("gpio: add Technologic I2C-FPGA gpio support") Signed-off-by: Mark Featherston Signed-off-by: Kris Bahnsen Signed-off-by: Bartosz Golaszewski Signed-off-by: Sasha Levin --- drivers/gpio/gpio-ts4900.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/drivers/gpio/gpio-ts4900.c b/drivers/gpio/gpio-ts4900.c index 1da8d0586329..410452306bf7 100644 --- a/drivers/gpio/gpio-ts4900.c +++ b/drivers/gpio/gpio-ts4900.c @@ -1,7 +1,7 @@ /* * Digital I/O driver for Technologic Systems I2C FPGA Core * - * Copyright (C) 2015 Technologic Systems + * Copyright (C) 2015, 2018 Technologic Systems * Copyright (C) 2016 Savoir-Faire Linux * * This program is free software; you can redistribute it and/or @@ -52,19 +52,33 @@ static int ts4900_gpio_direction_input(struct gpio_chip *chip, { struct ts4900_gpio_priv *priv = gpiochip_get_data(chip); - /* - * This will clear the output enable bit, the other bits are - * dontcare when this is cleared + /* Only clear the OE bit here, requires a RMW. Prevents potential issue + * with OE and data getting to the physical pin at different times. */ - return regmap_write(priv->regmap, offset, 0); + return regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OE, 0); } static int ts4900_gpio_direction_output(struct gpio_chip *chip, unsigned int offset, int value) { struct ts4900_gpio_priv *priv = gpiochip_get_data(chip); + unsigned int reg; int ret; + /* If changing from an input to an output, we need to first set the + * proper data bit to what is requested and then set OE bit. This + * prevents a glitch that can occur on the IO line + */ + regmap_read(priv->regmap, offset, ®); + if (!(reg & TS4900_GPIO_OE)) { + if (value) + reg = TS4900_GPIO_OUT; + else + reg &= ~TS4900_GPIO_OUT; + + regmap_write(priv->regmap, offset, reg); + } + if (value) ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE | TS4900_GPIO_OUT); -- 2.34.1