From 8786b095df02c1b881643146869a7d6f80411e6a Mon Sep 17 00:00:00 2001 From: Heiner Kallweit Date: Wed, 18 Jan 2023 22:55:12 +0100 Subject: [PATCH] i2c: gpio: support write-only sda/scl w/o pull-up 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. Handle the new attributes for write-only SDA and missing pull-up on SDA/SCL. For either pin the open-drain and has-no-pullup properties are mutually-exclusive, what is documented in the DT property documentation. We don't add an extra warning here because the open-drain properties are marked deprecated anyway. Signed-off-by: Heiner Kallweit [wsa: switched to device properties] Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-gpio.c | 13 ++++++++++--- include/linux/platform_data/i2c-gpio.h | 9 +++++++++ 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c index e4a5984..1794c03 100644 --- a/drivers/i2c/busses/i2c-gpio.c +++ b/drivers/i2c/busses/i2c-gpio.c @@ -317,6 +317,12 @@ static void i2c_gpio_get_properties(struct device *dev, device_property_read_bool(dev, "i2c-gpio,scl-open-drain"); pdata->scl_is_output_only = device_property_read_bool(dev, "i2c-gpio,scl-output-only"); + pdata->sda_is_output_only = + device_property_read_bool(dev, "i2c-gpio,sda-output-only"); + pdata->sda_has_no_pullup = + device_property_read_bool(dev, "i2c-gpio,sda-has-no-pullup"); + pdata->scl_has_no_pullup = + device_property_read_bool(dev, "i2c-gpio,scl-has-no-pullup"); } static struct gpio_desc *i2c_gpio_get_desc(struct device *dev, @@ -393,7 +399,7 @@ static int i2c_gpio_probe(struct platform_device *pdev) * handle them as we handle any other output. Else we enforce open * drain as this is required for an I2C bus. */ - if (pdata->sda_is_open_drain) + if (pdata->sda_is_open_drain || pdata->sda_has_no_pullup) gflags = GPIOD_OUT_HIGH; else gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; @@ -401,7 +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 || pdata->scl_has_no_pullup) gflags = GPIOD_OUT_HIGH; else gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; @@ -419,7 +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 a907774..545639b 100644 --- a/include/linux/platform_data/i2c-gpio.h +++ b/include/linux/platform_data/i2c-gpio.h @@ -16,16 +16,25 @@ * 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. + * @sda_has_no_pullup: SDA is used in a non-compliant way and has no pull-up. + * Therefore disable open-drain. * @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. + * @scl_has_no_pullup: SCL is used in a non-compliant way and has no pull-up. + * Therefore disable open-drain. */ 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 sda_has_no_pullup:1; unsigned int scl_is_open_drain:1; unsigned int scl_is_output_only:1; + unsigned int scl_has_no_pullup:1; }; #endif /* _LINUX_I2C_GPIO_H */ -- 2.7.4