From a29aaf55cd6faa75e35abfe00bd3ffc537490485 Mon Sep 17 00:00:00 2001 From: Moiz Sonasath Date: Tue, 16 Feb 2010 18:57:21 -0600 Subject: mfd: Disable TWL4030/5030 I2C1/I2C4 internal pull-ups This patch disables TWL4030/5030 I2C1 adn I2C4(SR) internal pull-up, to use only the external HW resistor >=470 Ohm for the assured functionality in HS mode. While testing the I2C in High Speed mode, it was discovered that without a proper pull-up resistor, there is data corruption during multi-byte transfer. RTC(time_set) test case was used for testing. From the analysis done, it was concluded that ideally we need a pull-up of 1.6k Ohm(recomended) or atleast 470 Ohm or greater for assured performance in HS mode. Signed-off-by: Moiz Sonasath Signed-off-by: Allen Pais Signed-off-by: Samuel Ortiz --- drivers/mfd/twl-core.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'drivers/mfd') diff --git a/drivers/mfd/twl-core.c b/drivers/mfd/twl-core.c index 942a1e83781..7ccc39f3aa4 100644 --- a/drivers/mfd/twl-core.c +++ b/drivers/mfd/twl-core.c @@ -958,6 +958,7 @@ twl_probe(struct i2c_client *client, const struct i2c_device_id *id) int status; unsigned i; struct twl4030_platform_data *pdata = client->dev.platform_data; + u8 temp; if (!pdata) { dev_dbg(&client->dev, "no platform data?\n"); @@ -1025,6 +1026,18 @@ twl_probe(struct i2c_client *client, const struct i2c_device_id *id) goto fail; } + /* Disable TWL4030/TWL5030 I2C Pull-up on I2C1 and I2C4(SR) interface. + * Program I2C_SCL_CTRL_PU(bit 0)=0, I2C_SDA_CTRL_PU (bit 2)=0, + * SR_I2C_SCL_CTRL_PU(bit 4)=0 and SR_I2C_SDA_CTRL_PU(bit 6)=0. + */ + + if (twl_class_is_4030()) { + twl_i2c_read_u8(TWL4030_MODULE_INTBR, &temp, REG_GPPUPDCTR1); + temp &= ~(SR_I2C_SDA_CTRL_PU | SR_I2C_SCL_CTRL_PU | \ + I2C_SDA_CTRL_PU | I2C_SCL_CTRL_PU); + twl_i2c_write_u8(TWL4030_MODULE_INTBR, temp, REG_GPPUPDCTR1); + } + status = add_children(pdata, id->driver_data); fail: if (status < 0) -- cgit v1.2.3