[PATCH] i2c: correct I2C deblock logic

[Alexander Kochetkov]

Hello Haibo Chen!

Setting GPIOD_ACTIVE_LOW has no effect. It filtered out by dm_gpio_set_dir_flags().
> 
> 
> if (bit)
> - dm_gpio_set_dir_flags(pin, GPIOD_IS_IN);
> + dm_gpio_set_dir_flags(pin, GPIOD_IS_IN |
> +    GPIOD_ACTIVE_LOW);

Here in original code GPIOD_ACTIVE_LOW has not effect.

else
    dm_gpio_set_dir_flags(pin, GPIOD_IS_OUT |
                                                GPIOD_ACTIVE_LOW |
                                                GPIOD_IS_OUT_ACTIVE);


This code actually fix problem with your DTS-settings:
> + return !dm_gpio_get_value(pin);


Can you debug and check using oscilloscope the code like this:

static void i2c_gpio_set_pin(struct gpio_desc *pin, int bit)
{
    ulong flags;
    ulong active;

    if (bit) {
        dm_gpio_set_dir_flags(pin, GPIOD_IS_IN);
    } else {
        dm_gpio_get_flags(pin, &flags);
        active = (flags & GPIOD_ACTIVE_LOW) ? GPIOD_IS_OUT_ACTIVE : 0;
        dm_gpio_set_dir_flags(pin, GPIOD_IS_OUT | active);
    }
}

static int i2c_gpio_get_pin(struct gpio_desc *pin)
{
     ulong flags;
     int value;

     value = dm_gpio_get_value(pin);
     return (flags & GPIOD_ACTIVE_LOW) ? !value : value;
}


> 10 февр. 2023 г., в 12:27, haibo.chen at nxp.com написал(а):
> 
> From: Haibo Chen <haibo.chen at nxp.com>
> 
> Current code use dm_gpio_get_value() to get SDA and SCL value, and the
> value depends on the flag GPIOD_ACTIVE_LOW. When toggle SCL to wait
> slave release SDA, the SDA are config as GPIOD_IS_IN, and whether contain
> the GPIOD_ACTIVE_LOW depends on the DTS setting. Usually, for I2C GPIO,
> we use GPIOD_ACTIVE_LOW flag in DTS, so if the SDA is in low level, then
> dm_gpio_get_value() will return 1, current code logic will stop the SCL
> toggle wrongly, cause the I2C deblock not work as expect.
> 
> This patch force set the GPIOD_ACTIVE_LOW for both GPIOD_IS_IN and
> GPIOD_IS_OUT, and make the return value of i2c_gpio_get_pin() eaqual to
> the physical voltage logic level.
> 
> Fixes: aa54192d4a87 ("dm: i2c: implement gpio-based I2C deblock")
> Signed-off-by: Haibo Chen <haibo.chen at nxp.com>
> ---
> drivers/i2c/i2c-uclass.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
> index 8d9a89ed89..4dc707c659 100644
> --- a/drivers/i2c/i2c-uclass.c
> +++ b/drivers/i2c/i2c-uclass.c
> @@ -505,7 +505,8 @@ uint i2c_get_chip_addr_offset_mask(struct udevice *dev)
> static void i2c_gpio_set_pin(struct gpio_desc *pin, int bit)
> {
> if (bit)
> - dm_gpio_set_dir_flags(pin, GPIOD_IS_IN);
> + dm_gpio_set_dir_flags(pin, GPIOD_IS_IN |
> +   GPIOD_ACTIVE_LOW);
> else
> dm_gpio_set_dir_flags(pin, GPIOD_IS_OUT |
>   GPIOD_ACTIVE_LOW |
> @@ -514,7 +515,7 @@ static void i2c_gpio_set_pin(struct gpio_desc *pin, int bit)
> 
> static int i2c_gpio_get_pin(struct gpio_desc *pin)
> {
> - return dm_gpio_get_value(pin);
> + return !dm_gpio_get_value(pin);
> }
> 
> int i2c_deblock_gpio_loop(struct gpio_desc *sda_pin,
> -- 
> 2.34.1
>