Add custom deblock dequence for the I2C bus, needed on some devices.
This sequence is issued once, when probing the driver, and is controlled
by DT property, "i2c-gpio,deblock".

Signed-off-by: Marek Vasut <ma...@denx.de>
---
 drivers/i2c/i2c-gpio.c | 67 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/drivers/i2c/i2c-gpio.c b/drivers/i2c/i2c-gpio.c
index 4e8fa21473..46975ef5c8 100644
--- a/drivers/i2c/i2c-gpio.c
+++ b/drivers/i2c/i2c-gpio.c
@@ -39,6 +39,11 @@ static int i2c_gpio_sda_get(struct gpio_desc *sda)
        return dm_gpio_get_value(sda);
 }
 
+static int i2c_gpio_scl_get(struct gpio_desc *scl)
+{
+       return dm_gpio_get_value(scl);
+}
+
 static void i2c_gpio_sda_set(struct gpio_desc *sda, int bit)
 {
        if (bit)
@@ -305,6 +310,67 @@ static int i2c_gpio_set_bus_speed(struct udevice *dev, 
unsigned int speed_hz)
        return 0;
 }
 
+/*
+ * I2C is a synchronous protocol and resets of the processor in the middle
+ * of an access can block the I2C Bus until a powerdown of the full unit is
+ * done. This function toggles the SCL until the SCL and SCA line are
+ * released, but max. 16 times, after this a I2C start-sequence is sent.
+ * This I2C Deblocking mechanism was developed by Keymile in association
+ * with Anatech and Atmel in 1998.
+ */
+static void i2c_gpio_make_abort(struct udevice *dev)
+{
+       struct i2c_gpio_bus *bus = dev_get_priv(dev);
+       struct gpio_desc *scl = &bus->gpios[PIN_SCL];
+       struct gpio_desc *sda = &bus->gpios[PIN_SDA];
+       int scl_state = 0;
+       int sda_state = 0;
+       int i = 0;
+       int ret = 0;
+
+#define DELAY_ABORT_SEQ        62      /* @200kHz 9 clocks = 44us, 62us is ok 
*/
+
+       i2c_gpio_scl_set(scl, 1);
+
+       if (!i2c_gpio_sda_get(sda)) {
+               ret = -1;
+               for (i = 0; i < 16; i++) {
+                       i2c_gpio_scl_set(scl, 0);
+                       udelay(DELAY_ABORT_SEQ);
+                       i2c_gpio_scl_set(scl, 1);
+                       udelay(DELAY_ABORT_SEQ);
+                       scl_state = i2c_gpio_scl_get(scl);
+                       sda_state = i2c_gpio_sda_get(sda);
+                       if (scl_state && sda_state) {
+                               ret = 0;
+                               break;
+                       }
+               }
+       }
+
+       if (!ret) {
+               for (i = 0; i < 5; i++) {
+                       i2c_gpio_send_start(scl, sda, 2 * bus->udelay);
+                       i2c_gpio_scl_set(scl, 0);
+               }
+       }
+
+       /* respect stop setup time */
+       udelay(DELAY_ABORT_SEQ);
+       i2c_gpio_scl_set(scl, 1);
+       udelay(DELAY_ABORT_SEQ);
+       i2c_gpio_sda_set(sda, 1);
+       i2c_gpio_sda_get(sda);
+}
+
+static int i2c_gpio_drv_probe(struct udevice *dev)
+{
+       if (dev_read_bool(dev, "i2c-gpio,deblock"))
+               i2c_gpio_make_abort(dev);
+
+       return 0;
+}
+
 static int i2c_gpio_ofdata_to_platdata(struct udevice *dev)
 {
        struct i2c_gpio_bus *bus = dev_get_priv(dev);
@@ -341,6 +407,7 @@ U_BOOT_DRIVER(i2c_gpio) = {
        .name   = "i2c-gpio",
        .id     = UCLASS_I2C,
        .of_match = i2c_gpio_ids,
+       .probe  = i2c_gpio_drv_probe,
        .ofdata_to_platdata = i2c_gpio_ofdata_to_platdata,
        .priv_auto_alloc_size = sizeof(struct i2c_gpio_bus),
        .ops    = &i2c_gpio_ops,
-- 
2.24.1

Reply via email to