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 <m-sonasath@ti.com>
Signed-off-by: Allen Pais <allen.pais@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/mfd/twl-core.c b/drivers/mfd/twl-core.c
index 942a1e837819..7ccc39f3aa48 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)