Re: [PATCH 1/2] omap: Disable TWL4030/5030 I2C1/I2C4 internal pull-ups

[Samuel Ortiz <sameo@linux.intel.com>]

Hi Moiz,

On Tue, Feb 16, 2010 at 06:57:21PM -0600, Moiz Sonasath wrote:
> 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.
Patch applied, many thanks.

Cheers,
Samuel.


> Signed-off-by: Moiz Sonasath <m-sonasath@ti.com>
> Signed-off-by: Allen Pais <allen.pais@ti.com>
> ---
>  drivers/mfd/twl-core.c  |   13 +++++++++++++
>  include/linux/i2c/twl.h |   15 +++++++++++++++
>  2 files changed, 28 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mfd/twl-core.c b/drivers/mfd/twl-core.c
> index 2a76065..35ae2ee 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");
> @@ -1032,6 +1033,18 @@ 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)
> diff --git a/include/linux/i2c/twl.h b/include/linux/i2c/twl.h
> index bf1c5be..fd95eca 100644
> --- a/include/linux/i2c/twl.h
> +++ b/include/linux/i2c/twl.h
> @@ -239,6 +239,21 @@ 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)
> +
> +/*----------------------------------------------------------------------*/
> +
>  /*
>   * Keypad register offsets (use TWL4030_MODULE_KEYPAD)
>   * ... SIH/interrupt only
> -- 
> 1.5.6.3
> 

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