From patchwork Sun Sep 10 21:44:22 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Linus Walleij X-Patchwork-Id: 812184 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-i2c-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.b="K9wnJTVx"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3xr4N173bfz9t2V for ; Mon, 11 Sep 2017 07:44:49 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751901AbdIJVos (ORCPT ); Sun, 10 Sep 2017 17:44:48 -0400 Received: from mail-lf0-f44.google.com ([209.85.215.44]:35104 "EHLO mail-lf0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751827AbdIJVos (ORCPT ); Sun, 10 Sep 2017 17:44:48 -0400 Received: by mail-lf0-f44.google.com with SMTP id d17so14433161lfe.2 for ; Sun, 10 Sep 2017 14:44:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=qamg7dzUxgSbxr03vx7pNM+c8xh7ROyHnpPPQZG2SdY=; b=K9wnJTVxh3aqlGk5rMXhFJ7HDpxxJjICrNJEnSzuZSl6Lkt3A0TZ532jflbhaUOyPj XZoF0GOJJZOLE3T028lJFYtpPDkOKGh+s1IaM1RiAGcw+6KJ9GuRc8h5xGmWt6rZr8wI oxUlXRBYh7k0EWhEdAkiaTPRGpTugN6PN/c6w= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=qamg7dzUxgSbxr03vx7pNM+c8xh7ROyHnpPPQZG2SdY=; b=I5xrA4Gh62DKi0SWYDX1ndURlS4yr5ndmXhNQgJyAPPIuqrpM7w2+RdSHlzVv3HFQT s3ACsbo1ef5tNZgu4RlwOwMHRcms9PEX+F2KW5ZIVQj2FxNQy+Sxewhj7qLhEmTra377 XD4VUpgROGVGEt5oy04L83T9Wp0NHHwY39bgRtcpZ+kxi87eLfSOr192S3XL7WMMvkff WvVcLFQUfUOyTV/ikiyU4dJghbS3uyArOog8QDMwqT4j06i2kk0PVvIbe6Q9dFqqtTPB j68O7FUJ9QNV2uYXNQjUsh2rqAvI9XNaSDTTVAhsfdlbSzhFE3SOWr+mg5SJNKJr/leb J8YQ== X-Gm-Message-State: AHPjjUjPL6lnQ/XB4wmeNprEgTg3XeR6LX1nnx5OyhY0rlJ5tUrEAIgy 8KKhts36tBJh9ljv X-Google-Smtp-Source: AOwi7QBsTEddbKcMVr9lo+LaMZfjoo6hYJNH57JHWlX93mwIvqoJWaPKSy/3QAxs6VZJOd6Hktb3/g== X-Received: by 10.46.4.220 with SMTP id a89mr3530476ljf.40.1505079886476; Sun, 10 Sep 2017 14:44:46 -0700 (PDT) Received: from fabina.bredbandsbolaget.se (c-2209e055.014-348-6c756e10.cust.bredbandsbolaget.se. [85.224.9.34]) by smtp.gmail.com with ESMTPSA id c69sm1461546ljd.42.2017.09.10.14.44.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 10 Sep 2017 14:44:45 -0700 (PDT) From: Linus Walleij To: Wolfram Sang , linux-i2c@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, adi-buildroot-devel@lists.sourceforge.net, Linus Walleij Subject: [PATCH 3/5] i2c: gpio: Enforce open drain through gpiolib Date: Sun, 10 Sep 2017 23:44:22 +0200 Message-Id: <20170910214424.14945-4-linus.walleij@linaro.org> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20170910214424.14945-1-linus.walleij@linaro.org> References: <20170910214424.14945-1-linus.walleij@linaro.org> Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org The I2C GPIO bitbang driver currently emulates open drain behaviour by implementing what the gpiolib already does: not actively driving the line high, instead setting it to input. This makes no sense. Use the new facility in gpiolib to request the lines enforced into open drain mode, and let the open drain emulation already present in the gpiolib kick in and handle this. As a bonus: if the GPIO driver in the back-end actually supports open drain in hardware using the .set_config() callback, it will be utilized. That's correct: we never used that hardware feature before, instead relying on emulating open drain even if the GPIO controller could actually handle this for us. Users will sometimes get messages like this: gpio-485 (?): enforced open drain please flag it properly in DT/ACPI DSDT/board file gpio-486 (?): enforced open drain please flag it properly in DT/ACPI DSDT/board file i2c-gpio gpio-i2c: using lines 485 (SDA) and 486 (SCL) Which is completely proper: since the line is used as open drain, it should actually be flagged properly with e.g. gpios = <&gpio0 5 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>, <&gpio0 6 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>; Or similar facilities in board file descriptor tables or ACPI DSDT. Signed-off-by: Linus Walleij --- drivers/i2c/busses/i2c-gpio.c | 102 ++++++++++++++++-------------------------- 1 file changed, 39 insertions(+), 63 deletions(-) diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c index 49e8b3ab30be..18ac4cf2ee75 100644 --- a/drivers/i2c/busses/i2c-gpio.c +++ b/drivers/i2c/busses/i2c-gpio.c @@ -25,23 +25,6 @@ struct i2c_gpio_private_data { struct i2c_gpio_platform_data pdata; }; -/* Toggle SDA by changing the direction of the pin */ -static void i2c_gpio_setsda_dir(void *data, int state) -{ - struct i2c_gpio_private_data *priv = data; - - /* - * This is a way of saying "do not drive - * me actively high" which means emulating open drain. - * The right way to do this is for gpiolib to - * handle this, by the function below. - */ - if (state) - gpiod_direction_input(priv->sda); - else - gpiod_direction_output(priv->sda, 0); -} - /* * Toggle SDA by changing the output value of the pin. This is only * valid for pins configured as open drain (i.e. setting the value @@ -54,17 +37,6 @@ static void i2c_gpio_setsda_val(void *data, int state) gpiod_set_value(priv->sda, state); } -/* Toggle SCL by changing the direction of the pin. */ -static void i2c_gpio_setscl_dir(void *data, int state) -{ - struct i2c_gpio_private_data *priv = data; - - if (state) - gpiod_direction_input(priv->scl); - else - gpiod_direction_output(priv->scl, 0); -} - /* * Toggle SCL by changing the output value of the pin. This is used * for pins that are configured as open drain and for output-only @@ -116,30 +88,13 @@ static int i2c_gpio_probe(struct platform_device *pdev) struct i2c_gpio_platform_data *pdata; struct i2c_algo_bit_data *bit_data; struct i2c_adapter *adap; + enum gpiod_flags gflags; int ret; priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); if (!priv) return -ENOMEM; - /* First get the GPIO pins; if it fails, we'll defer the probe. */ - priv->sda = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_HIGH); - if (IS_ERR(priv->sda)) { - ret = PTR_ERR(priv->sda); - /* FIXME: hack in the old code, is this really necessary? */ - if (ret == -EINVAL) - ret = -EPROBE_DEFER; - return ret; - } - priv->scl = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_OUT_LOW); - if (IS_ERR(priv->scl)) { - ret = PTR_ERR(priv->sda); - /* FIXME: hack in the old code, is this really necessary? */ - if (ret == -EINVAL) - ret = -EPROBE_DEFER; - return ret; - } - adap = &priv->adap; bit_data = &priv->bit_data; pdata = &priv->pdata; @@ -157,27 +112,48 @@ static int i2c_gpio_probe(struct platform_device *pdev) } /* - * FIXME: this is a hack emulating the open drain emulation - * that gpiolib can already do for us. Make all clients properly - * flag their lines as open drain and get rid of this property - * and the special callback. + * First get the GPIO pins; if it fails, we'll defer the probe. + * If the SDA line is marked from platform data or device tree as + * "open drain" it means something outside of our control is making + * this line being handled as open drain, and we should just handle + * it as any other output. Else we enforce open drain as this is + * required for an I2C bus. */ - if (pdata->sda_is_open_drain) { - gpiod_direction_output(priv->sda, 1); - bit_data->setsda = i2c_gpio_setsda_val; - } else { - gpiod_direction_input(priv->sda); - bit_data->setsda = i2c_gpio_setsda_dir; + if (pdata->sda_is_open_drain) + gflags = GPIOD_OUT_HIGH; + else + gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; + priv->sda = devm_gpiod_get_index(&pdev->dev, NULL, 0, gflags); + if (IS_ERR(priv->sda)) { + ret = PTR_ERR(priv->sda); + /* FIXME: hack in the old code, is this really necessary? */ + if (ret == -EINVAL) + ret = -EPROBE_DEFER; + return ret; } - - if (pdata->scl_is_open_drain || pdata->scl_is_output_only) { - gpiod_direction_output(priv->scl, 1); - bit_data->setscl = i2c_gpio_setscl_val; - } else { - gpiod_direction_input(priv->scl); - bit_data->setscl = i2c_gpio_setscl_dir; + /* + * If the SCL line is marked from platform data or device tree as + * "open drain" it means something outside of our control is making + * this line being handled as open drain, and we should just handle + * it as any other output. Else we enforce open drain as this is + * required for an I2C bus. + */ + if (pdata->scl_is_open_drain) + gflags = GPIOD_OUT_LOW; + else + gflags = GPIOD_OUT_LOW_OPEN_DRAIN; + priv->scl = devm_gpiod_get_index(&pdev->dev, NULL, 1, gflags); + if (IS_ERR(priv->scl)) { + ret = PTR_ERR(priv->sda); + /* FIXME: hack in the old code, is this really necessary? */ + if (ret == -EINVAL) + ret = -EPROBE_DEFER; + return ret; } + bit_data->setsda = i2c_gpio_setsda_val; + bit_data->setscl = i2c_gpio_setscl_val; + if (!pdata->scl_is_output_only) bit_data->getscl = i2c_gpio_getscl; bit_data->getsda = i2c_gpio_getsda;