From a40fe217d19fdb9804fdc88342ce4bb0a0440c84 Mon Sep 17 00:00:00 2001 From: Lukasz Majewski Date: Thu, 4 Apr 2019 12:35:34 +0200 Subject: 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 --- doc/device-tree-bindings/i2c/i2c.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'doc') 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 @@ property which allows the chip offset length to be selected. 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 = , ; pinctrl-names = "default", "gpio"; pinctrl-0 = <&i2c_xfer>; @@ -28,6 +32,7 @@ i2c4: i2c@12ca0000 { 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>; }; }; -- cgit v1.1