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/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),