Add simple description of iMX6 HDMI DDC controller used as a I2C master. Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx> Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> Cc: linux-i2c@xxxxxxxxxxxxxxx --- Documentation/i2c/busses/i2c-imx-hdmi | 62 +++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 Documentation/i2c/busses/i2c-imx-hdmi diff --git a/Documentation/i2c/busses/i2c-imx-hdmi b/Documentation/i2c/busses/i2c-imx-hdmi new file mode 100644 index 0000000..20c7101 --- /dev/null +++ b/Documentation/i2c/busses/i2c-imx-hdmi @@ -0,0 +1,62 @@ +Kernel driver i2c-imx-hdmi + +Supported adapters: + * Freescale iMX6Quad HDMI controller + * Freescale iMX6DualLite HDMI controller + * Freescale iMX6Solo HDMI controller + +Datasheets: + Publicly available at the Freescale website + +Authors: + Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx> + + +Description +----------- + +According to the iMX6 Reference Manual only two types of transactions +are supported by HDMI I2C Master Interface in Normal Mode: + +A) one byte data write transaction (I2C spec write/write transmission): + + master S|slave addr[6:0]|0| |slave reg[7:0]| |data[7:0]| |P + slave | ack | | ack | | ack | + +B) one byte data read transaction (I2C spec write/read combined format): + + master S|slave addr[6:0]|0| |slave reg[7:0]| | ... + slave | ack | | ack | ... + + master ... Sr|slave addr[6:0]|1| | | ack |P + slave ... | Ack |data[7:0]| + +HDMI I2C Master Interface Extended Read Mode allows to execute one +more transaction pattern so called segment pointer-based read: + +C) segment pointer-based read (I2C spec write/write/read combined format): + + master S|seg addr[6:0]|0| |seg pointer[7:0]| | ... + slave | xxx | | xxx | ... + + master ... Sr|slave addr[6:0]|0| |slave reg[7:0]| | ... + slave ... | ack | | ack | ... + + master ... Sr|slave addr[6:0]|1| | | ack |P + slave ... | ack |data[7:0]| + +At the moment Extended Read Mode is not supported by the driver. + +The technical limitations of the iMX6 HDMI E-DDC bus does not allow +to call it an I2C compatible bus, however relativery large subset of +I2C transactions can be decomposed into aforementioned data read/write +operations and many I2C devices correctly support those operations, +but the primary goad of the device is to read EDID blob of a connected +HDMI monitor. + + +Notes +----- + +The bus driver may be used independently on HDMI controller, but due +to device limitations it can not support arbitrary slave devices. -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
