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.auch...@ni.com>
Cc: Heiko Schocher <h...@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
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