Marc Jones (marc.jones@se-eng.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/7952
-gerrit
commit e20faa8f82074210ef3fe13d73e1be3c7ab3afcb Author: Ken Chang kenc@nvidia.com Date: Thu May 22 10:54:16 2014 +0800
nyan*: Set GEN2 I2C pads to open-drain mode
The VDDIO to GEN2 I2C SCL/SDA pins is 1.8V and the external pull-up voltage is 3.3V (the external 3.3V > I/O 1.8V) thus the pinmux E_OD bit of these two pins needs to be set to ensure GEN2 I2C pads work fine on 3.3V.
BRANCH=nyan BUG=none TEST=observed voltage drop from 3.3V to 2.36V on gen2 i2c on blaze w/o this change. the waveform looks good on both scl/sda pins w/ this change.
Original-Change-Id: I1b97f0c9c7580d1e532c3bdf7ac8690241ee7ee3 Original-Signed-off-by: Ken Chang kenc@nvidia.com Original-Reviewed-on: https://chromium-review.googlesource.com/200996 Original-Reviewed-by: Julius Werner jwerner@chromium.org (cherry picked from commit 2db39166ec525e56a19746f38a867305a2687365) Signed-off-by: Marc Jones marc.jones@se-eng.com
Change-Id: I0c84eade89311baf0a6f180cb5cc9e2145f6b7ea --- src/mainboard/google/nyan/mainboard.c | 6 ++++-- src/mainboard/google/nyan_big/mainboard.c | 6 ++++-- src/mainboard/google/nyan_blaze/mainboard.c | 6 ++++-- 3 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/src/mainboard/google/nyan/mainboard.c b/src/mainboard/google/nyan/mainboard.c index a54f95d..682fdc4 100644 --- a/src/mainboard/google/nyan/mainboard.c +++ b/src/mainboard/google/nyan/mainboard.c @@ -81,10 +81,12 @@ static void setup_pinmux(void) PINMUX_GEN1_I2C_SDA_FUNC_I2C1 | PINMUX_INPUT_ENABLE); // I2C2 clock. pinmux_set_config(PINMUX_GEN2_I2C_SCL_INDEX, - PINMUX_GEN2_I2C_SCL_FUNC_I2C2 | PINMUX_INPUT_ENABLE); + PINMUX_GEN2_I2C_SCL_FUNC_I2C2 | PINMUX_INPUT_ENABLE | + PINMUX_OPEN_DRAIN); // I2C2 data. pinmux_set_config(PINMUX_GEN2_I2C_SDA_INDEX, - PINMUX_GEN2_I2C_SDA_FUNC_I2C2 | PINMUX_INPUT_ENABLE); + PINMUX_GEN2_I2C_SDA_FUNC_I2C2 | PINMUX_INPUT_ENABLE | + PINMUX_OPEN_DRAIN); // I2C4 (DDC) clock. pinmux_set_config(PINMUX_DDC_SCL_INDEX, PINMUX_DDC_SCL_FUNC_I2C4 | PINMUX_INPUT_ENABLE); diff --git a/src/mainboard/google/nyan_big/mainboard.c b/src/mainboard/google/nyan_big/mainboard.c index 4a55e1e..ff147e2 100644 --- a/src/mainboard/google/nyan_big/mainboard.c +++ b/src/mainboard/google/nyan_big/mainboard.c @@ -81,10 +81,12 @@ static void setup_pinmux(void) PINMUX_GEN1_I2C_SDA_FUNC_I2C1 | PINMUX_INPUT_ENABLE); // I2C2 clock. pinmux_set_config(PINMUX_GEN2_I2C_SCL_INDEX, - PINMUX_GEN2_I2C_SCL_FUNC_I2C2 | PINMUX_INPUT_ENABLE); + PINMUX_GEN2_I2C_SCL_FUNC_I2C2 | PINMUX_INPUT_ENABLE | + PINMUX_OPEN_DRAIN); // I2C2 data. pinmux_set_config(PINMUX_GEN2_I2C_SDA_INDEX, - PINMUX_GEN2_I2C_SDA_FUNC_I2C2 | PINMUX_INPUT_ENABLE); + PINMUX_GEN2_I2C_SDA_FUNC_I2C2 | PINMUX_INPUT_ENABLE | + PINMUX_OPEN_DRAIN); // I2C4 (DDC) clock. pinmux_set_config(PINMUX_DDC_SCL_INDEX, PINMUX_DDC_SCL_FUNC_I2C4 | PINMUX_INPUT_ENABLE); diff --git a/src/mainboard/google/nyan_blaze/mainboard.c b/src/mainboard/google/nyan_blaze/mainboard.c index 0c5078f..8d4f553 100644 --- a/src/mainboard/google/nyan_blaze/mainboard.c +++ b/src/mainboard/google/nyan_blaze/mainboard.c @@ -81,10 +81,12 @@ static void setup_pinmux(void) PINMUX_GEN1_I2C_SDA_FUNC_I2C1 | PINMUX_INPUT_ENABLE); // I2C2 clock. pinmux_set_config(PINMUX_GEN2_I2C_SCL_INDEX, - PINMUX_GEN2_I2C_SCL_FUNC_I2C2 | PINMUX_INPUT_ENABLE); + PINMUX_GEN2_I2C_SCL_FUNC_I2C2 | PINMUX_INPUT_ENABLE | + PINMUX_OPEN_DRAIN); // I2C2 data. pinmux_set_config(PINMUX_GEN2_I2C_SDA_INDEX, - PINMUX_GEN2_I2C_SDA_FUNC_I2C2 | PINMUX_INPUT_ENABLE); + PINMUX_GEN2_I2C_SDA_FUNC_I2C2 | PINMUX_INPUT_ENABLE | + PINMUX_OPEN_DRAIN); // I2C4 (DDC) clock. pinmux_set_config(PINMUX_DDC_SCL_INDEX, PINMUX_DDC_SCL_FUNC_I2C4 | PINMUX_INPUT_ENABLE);