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i2c: gpio: support write-only sda/scl w/o pull-up

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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 <hkallweit1@gmail.com>
[wsa: switched to device properties]
Signed-off-by: Wolfram Sang <wsa@kernel.org>
This commit is contained in:
Heiner Kallweit 2023-01-18 22:55:12 +01:00 committed by Wolfram Sang
parent 9dfee1487c
commit 8786b095df
2 changed files with 19 additions and 3 deletions
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13
drivers/i2c/busses/i2c-gpio.c
View File

@ -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;

9
include/linux/platform_data/i2c-gpio.h
View File

@ -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 */