>From 4044fcc9c517e86fbea9f7d3b15d5cf75a767476 Mon Sep 17 00:00:00 2001
From: Allen Pais <allen.pais@xxxxxx>
Date: Thu, 21 Jan 2010 21:00:04 +0530
Subject: [PATCH 1/2] omap: Disable GAIA I2C1/I2C4 internal pull-ups
This patch disables GAIA 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@xxxxxx>
Signed-off-by: Allen Pais <allen.pais@xxxxxx>
---
drivers/mfd/twl-core.c | 10 ++++++++++
include/linux/i2c/twl.h | 13 +++++++++++++
2 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/drivers/mfd/twl-core.c b/drivers/mfd/twl-core.c
index 2a76065..7dcb5e9 100644
--- a/drivers/mfd/twl-core.c
+++ b/drivers/mfd/twl-core.c
@@ -965,6 +965,7 @@ 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");
@@ -1031,6 +1032,15 @@ twl_probe(struct i2c_client *client, const struct i2c_device_id *id)
if (status < 0)
goto fail;
}
+ /* Disable GAIA 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.
+ */
+
+ 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:
diff --git a/include/linux/i2c/twl.h b/include/linux/i2c/twl.h
index bf1c5be..2f4faf9 100644
--- a/include/linux/i2c/twl.h
+++ b/include/linux/i2c/twl.h
@@ -168,6 +168,19 @@ int twl_i2c_read(u8 mod_no, u8 *value, u8 reg, unsigned num_bytes);
int twl6030_interrupt_unmask(u8 bit_mask, u8 offset);
int twl6030_interrupt_mask(u8 bit_mask, u8 offset);
+/*Interface Bit Register (INTBR) offsets
+ *(Use TWL_4030_MODULE_INTBR)
+ */
+
+#define REG_GPPUPDCTR1 0x0F
+
+/*I2C1 and I2C4(SR) SDA/SCL pull-up control bits */
+
+#define I2C_SCL_CTRL_PU BIT(0)
+#define I2C_SDA_CTRL_PU BIT(2)
+#define SR_I2C_SCL_CTRL_PU BIT(4)
+#define SR_I2C_SDA_CTRL_PU BIT(6)
+
/*----------------------------------------------------------------------*/
/*
--
1.6.3.3
--
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