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[2a01:c22:6e61:8c00:154f:326e:8d45:8ce7]) by smtp.googlemail.com with ESMTPSA id k2-20020a5d5182000000b00236545edc91sm23789073wrv.76.2023.01.15.02.18.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 15 Jan 2023 02:18:29 -0800 (PST) Message-ID: Date: Sun, 15 Jan 2023 11:18:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Content-Language: en-US From: Heiner Kallweit To: Rob Herring , Krzysztof Kozlowski , Wolfram Sang Cc: "linux-i2c@vger.kernel.org" , "devicetree@vger.kernel.org" References: <3a5545f3-f858-2c80-8bd4-2e0d401a1dc0@gmail.com> Subject: [PATCH v3 3/3] i2c: gpio: support write-only sda In-Reply-To: <3a5545f3-f858-2c80-8bd4-2e0d401a1dc0@gmail.com> X-Spam-Status: No, score=-1.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org There are slave devices that understand I2C but have read-only SDA and SCL. Examples are FD650 7-segment LED controller and its derivatives. Typical board designs don't even have a pull-up for both pins. Therefore don't enforce open-drain if SDA and SCL both are unidirectional. This patch makes i2c-gpio usable with such devices, based on new DT property i2c-gpio,sda-output-only. Signed-off-by: Heiner Kallweit --- v3: - improve description of attribute sda_is_output_only --- drivers/i2c/busses/i2c-gpio.c | 14 +++++++++++--- include/linux/platform_data/i2c-gpio.h | 3 +++ 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c index 0e4385a9b..ea108d7e4 100644 --- a/drivers/i2c/busses/i2c-gpio.c +++ b/drivers/i2c/busses/i2c-gpio.c @@ -316,6 +316,8 @@ static void of_i2c_gpio_get_props(struct device_node *np, of_property_read_bool(np, "i2c-gpio,scl-open-drain"); pdata->scl_is_output_only = of_property_read_bool(np, "i2c-gpio,scl-output-only"); + pdata->sda_is_output_only = + of_property_read_bool(np, "i2c-gpio,sda-output-only"); } static struct gpio_desc *i2c_gpio_get_desc(struct device *dev, @@ -363,6 +365,7 @@ static int i2c_gpio_probe(struct platform_device *pdev) struct device *dev = &pdev->dev; struct device_node *np = dev->of_node; enum gpiod_flags gflags; + bool sda_scl_output_only; int ret; priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); @@ -391,8 +394,12 @@ static int i2c_gpio_probe(struct platform_device *pdev) * marking these lines to be handled as open drain, and we should just * handle them as we handle any other output. Else we enforce open * drain as this is required for an I2C bus. + * If SCL/SDA both are write-only, then this indicates I2C-like slaves + * with read-only SCL/SDA. Such slaves don't need open-drain, and partially + * don't even work with open-drain. */ - if (pdata->sda_is_open_drain) + sda_scl_output_only = pdata->sda_is_output_only && pdata->scl_is_output_only; + if (pdata->sda_is_open_drain || sda_scl_output_only) gflags = GPIOD_OUT_HIGH; else gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; @@ -400,7 +407,7 @@ static int i2c_gpio_probe(struct platform_device *pdev) if (IS_ERR(priv->sda)) return PTR_ERR(priv->sda); - if (pdata->scl_is_open_drain) + if (pdata->scl_is_open_drain || sda_scl_output_only) gflags = GPIOD_OUT_HIGH; else gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; @@ -418,7 +425,8 @@ static int i2c_gpio_probe(struct platform_device *pdev) if (!pdata->scl_is_output_only) bit_data->getscl = i2c_gpio_getscl; - bit_data->getsda = i2c_gpio_getsda; + if (!pdata->sda_is_output_only) + bit_data->getsda = i2c_gpio_getsda; if (pdata->udelay) bit_data->udelay = pdata->udelay; diff --git a/include/linux/platform_data/i2c-gpio.h b/include/linux/platform_data/i2c-gpio.h index a907774fd..e9536c078 100644 --- a/include/linux/platform_data/i2c-gpio.h +++ b/include/linux/platform_data/i2c-gpio.h @@ -16,6 +16,8 @@ * isn't actively driven high when setting the output value high. * gpio_get_value() must return the actual pin state even if the * pin is configured as an output. + * @sda_is_output_only: SDA output drivers can't be turned off. + * This is for clients that can only read SDA/SCL. * @scl_is_open_drain: SCL is set up as open drain. Same requirements * as for sda_is_open_drain apply. * @scl_is_output_only: SCL output drivers cannot be turned off. @@ -24,6 +26,7 @@ struct i2c_gpio_platform_data { int udelay; int timeout; unsigned int sda_is_open_drain:1; + unsigned int sda_is_output_only:1; unsigned int scl_is_open_drain:1; unsigned int scl_is_output_only:1; };