Commit 8786b095 authored by Heiner Kallweit's avatar Heiner Kallweit Committed by Wolfram Sang
Browse files

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: default avatarHeiner Kallweit <hkallweit1@gmail.com>
[wsa: switched to device properties]
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent 9dfee148

drivers/i2c/busses/i2c-gpio.c

+10 −3
Original line number Diff line number Diff line
@@ -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;
@@ -419,6 +425,7 @@ static int i2c_gpio_probe(struct platform_device *pdev) 


	if (!pdata->scl_is_output_only)

		bit_data->getscl = i2c_gpio_getscl;

	if (!pdata->sda_is_output_only)

		bit_data->getsda = i2c_gpio_getsda;



	if (pdata->udelay)

include/linux/platform_data/i2c-gpio.h

+9 −0
Original line number Diff line number Diff line
@@ -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 */