________________________________________
From: Tony Lindgren [tony@xxxxxxxxxxx]
Sent: Monday, February 01, 2010 7:53 PM
To: Pais, Allen
Cc: linux-omap@xxxxxxxxxxxxxxx
Subject: Re: [PATCH 1/2] omap: Disable GAIA I2C1/I2C4 internal pull-ups
Hi,
* Pais, Allen <allen.pais@xxxxxx> [100121 02:31]:
> 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.
Does this apply to 3630 only, or also 34xx? Is this safe to do
always?
[Allen] Yes, it does apply to 36xx only.
BTW, once ready it hould be sent to Samuel Ortiz with linux-omap
list Cc'd:
[Allen] i'll have it sent to Samuel also.
Thanks,
- Allen
$ grep -A4 MFD MAINTAINERS
MULTIFUNCTION DEVICES (MFD)
M: Samuel Ortiz <sameo@xxxxxxxxxxxxxxx>
T: git git://git.kernel.org/pub/scm/linux/kernel/git/sameo/mfd-2.6.git
S: Supported
F: drivers/mfd/
Regards,
Tony
> 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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