Hello Moiz,
On Wed, Feb 17, 2010 at 01:57:21AM +0100, ext 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.
Nice findings!
>
> >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 | 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()) {
Is this run time check sufficient enough to determine if this fix must be applied?
>From what you have described on you patch description, looks like it is supposed to be
only for HS mode. I don't know, maybe if you bind this to a platform / board configuration
flag would it be better? I mean, you create a flag inside the platform data to determine
if this fix must be applied or not. At least for me, having an external pu resistor
seams to be very board dependent.
> + 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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--
Eduardo Valentin
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