From ba6fb2f6aca54c6555742d507290cbfaa655e623 Mon Sep 17 00:00:00 2001 From: Heiko Schocher Date: Mon, 16 Mar 2020 07:55:06 +0100 Subject: [PATCH] dm: i2c-gpio: add support for clock stretching 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). This is enabled by default; for gpios which cannot be configured as inputs, the i2c-gpio,scl-output-only property can be used to fall back to the previous behavior. Signed-off-by: Michael Auchter Cc: Heiko Schocher Reviewed-by: Heiko Schocher --- doc/device-tree-bindings/i2c/i2c-gpio.txt | 2 ++ drivers/i2c/i2c-gpio.c | 23 ++++++++++++++++++++++- 2 files changed, 24 insertions(+), 1 deletion(-) diff --git a/doc/device-tree-bindings/i2c/i2c-gpio.txt b/doc/device-tree-bindings/i2c/i2c-gpio.txt index e29eeba9e6..b06b829933 100644 --- a/doc/device-tree-bindings/i2c/i2c-gpio.txt +++ b/doc/device-tree-bindings/i2c/i2c-gpio.txt @@ -18,6 +18,8 @@ Optional: It not defined, then default is 5us (~50KHz). * i2c-gpio,deblock Run deblocking sequence when the driver gets probed. +* i2c-gpio,scl-output-only; + Set if SCL is an output only Example: diff --git a/drivers/i2c/i2c-gpio.c b/drivers/i2c/i2c-gpio.c index e3a21ad3b2..07fdd343f2 100644 --- a/drivers/i2c/i2c-gpio.c +++ b/drivers/i2c/i2c-gpio.c @@ -56,6 +56,24 @@ static void i2c_gpio_sda_set(struct i2c_gpio_bus *bus, int bit) } static void i2c_gpio_scl_set(struct i2c_gpio_bus *bus, int bit) +{ + struct gpio_desc *scl = &bus->gpios[PIN_SCL]; + int count = 0; + + 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); + } +} + +/* variant for output only gpios which cannot support clock stretching */ +static void i2c_gpio_scl_set_output_only(struct i2c_gpio_bus *bus, int bit) { struct gpio_desc *scl = &bus->gpios[PIN_SCL]; ulong flags = GPIOD_IS_OUT; @@ -328,7 +346,10 @@ static int i2c_gpio_ofdata_to_platdata(struct udevice *dev) bus->get_sda = i2c_gpio_sda_get; bus->set_sda = i2c_gpio_sda_set; - bus->set_scl = i2c_gpio_scl_set; + if (fdtdec_get_bool(blob, node, "i2c-gpio,scl-output-only")) + bus->set_scl = i2c_gpio_scl_set_output_only; + else + bus->set_scl = i2c_gpio_scl_set; return 0; error: