| Message ID | 20200123223009.213180-1-michael.auchter@ni.com |
|---|---|
| State | New |
| Headers | show |
| Series | dm: i2c-gpio: add support for clock stretching | expand |
Hello Michael, Am 23.01.2020 um 23:30 schrieb Michael Auchter: > This adds support for clock stretching to the i2c-gpio driver. This is > accomplished by switching the GPIO used for the SCL line to an input > when it should be driven high, and polling on the SCL line value until > it goes high (indicating that the I2C slave is no longer pulling it > low). > > Signed-off-by: Michael Auchter <michael.auchter at ni.com> > Cc: Heiko Schocher <hs at denx.de> > --- > drivers/i2c/i2c-gpio.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/drivers/i2c/i2c-gpio.c b/drivers/i2c/i2c-gpio.c > index 4e8fa21473..80ac26e583 100644 > --- a/drivers/i2c/i2c-gpio.c > +++ b/drivers/i2c/i2c-gpio.c > @@ -49,11 +49,18 @@ static void i2c_gpio_sda_set(struct gpio_desc *sda, int bit) > > static void i2c_gpio_scl_set(struct gpio_desc *scl, int bit) > { > - ulong flags = GPIOD_IS_OUT; > + int count = 0; > > - if (bit) > - flags |= GPIOD_IS_OUT_ACTIVE; > - dm_gpio_set_dir_flags(scl, flags); > + if (bit) { > + dm_gpio_set_dir_flags(scl, GPIOD_IS_IN); > + while (!dm_gpio_get_value(scl) && count++ < 100000) > + udelay(1); > + > + if (!dm_gpio_get_value(scl)) > + pr_err("timeout waiting on slave to release scl\n"); > + } else { > + dm_gpio_set_dir_flags(scl, GPIOD_IS_OUT); > + } > } > > static void i2c_gpio_write_bit(struct gpio_desc *scl, struct gpio_desc *sda, > In principle I would say Ok, but your patch changes behaviour for all boards which use this driver currently ... May they cannot reread the gpio ... we have no scl_get() yet! So please, make this change dependend on linux property "i2c-gpio,scl-output-only" see: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/i2c/i2c-gpio.yaml#n36 As an example in linux: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/i2c/busses/i2c-gpio.c#n317 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/i2c/algos/i2c-algo-bit.c#n75 So at least, we have the chance to switch back to old behaviour by adding this (new for U-Boot) property. Thanks! bye, Heiko
diff --git a/drivers/i2c/i2c-gpio.c b/drivers/i2c/i2c-gpio.c index 4e8fa21473..80ac26e583 100644 --- a/drivers/i2c/i2c-gpio.c +++ b/drivers/i2c/i2c-gpio.c @@ -49,11 +49,18 @@ static void i2c_gpio_sda_set(struct gpio_desc *sda, int bit) static void i2c_gpio_scl_set(struct gpio_desc *scl, int bit) { - ulong flags = GPIOD_IS_OUT; + int count = 0; - if (bit) - flags |= GPIOD_IS_OUT_ACTIVE; - dm_gpio_set_dir_flags(scl, flags); + if (bit) { + dm_gpio_set_dir_flags(scl, GPIOD_IS_IN); + while (!dm_gpio_get_value(scl) && count++ < 100000) + udelay(1); + + if (!dm_gpio_get_value(scl)) + pr_err("timeout waiting on slave to release scl\n"); + } else { + dm_gpio_set_dir_flags(scl, GPIOD_IS_OUT); + } } static void i2c_gpio_write_bit(struct gpio_desc *scl, struct gpio_desc *sda,
This adds support for clock stretching to the i2c-gpio driver. This is accomplished by switching the GPIO used for the SCL line to an input when it should be driven high, and polling on the SCL line value until it goes high (indicating that the I2C slave is no longer pulling it low). Signed-off-by: Michael Auchter <michael.auchter at ni.com> Cc: Heiko Schocher <hs at denx.de> --- drivers/i2c/i2c-gpio.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)