DM: I2C: Introduce 'u-boot, i2c-transaction-bytes' property
The 'u-boot,i2c-transaction-bytes' device tree property provides
information regarding number of bytes transferred by a device in a
single transaction.
This change is necessary to avoid hanging devices after soft reset.
One notable example is communication with MC34708 device:
1. Reset when communicating with MC34708 via I2C.
2. The u-boot (after reboot -f) tries to setup the I2C and then calls
force_idle_bus. In the same time MC34708 still has some data to be sent
(as it transfers data in 24 bits chunks).
3. The force_idle_bus() is not able to make the bus idle as 8 SCL
clocks may be not enough to have the full transmission.
4. We end up with I2C inconsistency with MC34708.
This PMIC device requires 24+ SCL cycles to make finish any pending I2C
transmission.
Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/doc/device-tree-bindings/i2c/i2c.txt b/doc/device-tree-bindings/i2c/i2c.txt
index de818d4..9698e48 100644
--- a/doc/device-tree-bindings/i2c/i2c.txt
+++ b/doc/device-tree-bindings/i2c/i2c.txt
@@ -12,6 +12,10 @@
Optional properties:
- u-boot,i2c-offset-len - length of chip offset in bytes. If omitted the
default value of 1 is used.
+- u-boot,i2c-transaction-bytes - the length of single I2C transaction on
+ the bus. Some devices require more than single byte transmission
+ (e.g. mc34708 mfd). This information is necessary to correctly
+ initialize (put into idle state) I2C bus after soft reset.
- gpios = <sda ...>, <scl ...>;
pinctrl-names = "default", "gpio";
pinctrl-0 = <&i2c_xfer>;
@@ -28,6 +32,7 @@
compatible = "google,cros-ec";
i2c-max-frequency = <100000>;
u-boot,i2c-offset-len = <0>;
+ u-boot,i2c-transaction-bytes = <3>;
ec-interrupt = <&gpx1 6 GPIO_ACTIVE_LOW>;
};
};
diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
index 49e23a0..e47abf1 100644
--- a/drivers/i2c/i2c-uclass.c
+++ b/drivers/i2c/i2c-uclass.c
@@ -593,6 +593,29 @@
}
#endif
+static int i2c_pre_probe(struct udevice *dev)
+{
+#if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)
+ struct dm_i2c_bus *i2c = dev_get_uclass_priv(dev);
+ unsigned int max = 0;
+ ofnode node;
+ int ret;
+
+ i2c->max_transaction_bytes = 0;
+ dev_for_each_subnode(node, dev) {
+ ret = ofnode_read_u32(node,
+ "u-boot,i2c-transaction-bytes",
+ &max);
+ if (!ret && max > i2c->max_transaction_bytes)
+ i2c->max_transaction_bytes = max;
+ }
+
+ debug("%s: I2C bus: %s max transaction bytes: %d\n", __func__,
+ dev->name, i2c->max_transaction_bytes);
+#endif
+ return 0;
+}
+
static int i2c_post_probe(struct udevice *dev)
{
#if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)
@@ -674,6 +697,7 @@
.post_bind = i2c_post_bind,
.init = i2c_uclass_init,
.priv_auto_alloc_size = sizeof(struct i2c_priv),
+ .pre_probe = i2c_pre_probe,
.post_probe = i2c_post_probe,
.per_device_auto_alloc_size = sizeof(struct dm_i2c_bus),
.per_child_platdata_auto_alloc_size = sizeof(struct dm_i2c_chip),
diff --git a/drivers/i2c/mxc_i2c.c b/drivers/i2c/mxc_i2c.c
index 9999d9f..5420afb 100644
--- a/drivers/i2c/mxc_i2c.c
+++ b/drivers/i2c/mxc_i2c.c
@@ -354,9 +354,10 @@
int i2c_idle_bus(struct mxc_i2c_bus *i2c_bus)
{
struct udevice *bus = i2c_bus->bus;
+ struct dm_i2c_bus *i2c = dev_get_uclass_priv(bus);
struct gpio_desc *scl_gpio = &i2c_bus->scl_gpio;
struct gpio_desc *sda_gpio = &i2c_bus->sda_gpio;
- int sda, scl;
+ int sda, scl, idle_sclks;
int i, ret = 0;
ulong elapsed, start_time;
@@ -380,8 +381,22 @@
if ((sda & scl) == 1)
goto exit; /* Bus is idle already */
+ /*
+ * In most cases it is just enough to generate 8 + 1 SCLK
+ * clocks to recover I2C slave device from 'stuck' state
+ * (when for example SW reset was performed, in the middle of
+ * I2C transmission).
+ *
+ * However, there are devices which send data in packets of
+ * N bytes (N > 1). In such case we do need N * 8 + 1 SCLK
+ * clocks.
+ */
+ idle_sclks = 8 + 1;
+
+ if (i2c->max_transaction_bytes > 0)
+ idle_sclks = i2c->max_transaction_bytes * 8 + 1;
/* Send high and low on the SCL line */
- for (i = 0; i < 9; i++) {
+ for (i = 0; i < idle_sclks; i++) {
dm_gpio_set_dir_flags(scl_gpio, GPIOD_IS_OUT);
dm_gpio_set_value(scl_gpio, 0);
udelay(50);
diff --git a/include/i2c.h b/include/i2c.h
index ccffc19..a5c760c 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -68,9 +68,11 @@
* I2C bus udevice.
*
* @speed_hz: Bus speed in hertz (typically 100000)
+ * @max_transaction_bytes: Maximal size of single I2C transfer
*/
struct dm_i2c_bus {
int speed_hz;
+ int max_transaction_bytes;
};
/*