[PATCHv2 2/3] ARM: mxs: cfa10049: Switch bus i2c1 to bitbanging

Fabio Estevam festevam at gmail.com
Tue Jul 2 09:57:04 EDT 2013

Hi Christoph,

On Tue, Jul 2, 2013 at 10:29 AM, Christoph G. Baumann <cb at sgoc.de> wrote:
> Hello Alexandre,
>> The ADCs connected to this bus have been experiencing some timeout
>> issues when using the iMX28 i2c controller. Switching back to bitbanging
>> solves this.
> the chip errata for i.MX23(!) contains an issue (no 2727) with the I2C
> controller that is also applicable for the i.MX28:
> "
> 2727 I2C 9th Clock Pulse (ACK) not generated when RETAIN_CLOCK set.
> Description:
> When RETAIN_CLOCK is set, the ninth clock pulse (ACK) is not generated. However,
> the SDA
> line is read at the proper timing interval. If RETAIN_CLOCK is cleared, the
> ninth clock pulse is
> generated.
> Also, the HW_I2C_VERSION register incorrectly states the version is 1.2. It
> should be 1.3.
> Workaround:
> HW_I2C_CTRL1[ACK_MODE] has default value of 0. It should be set to 1 to enable
> the fix for
> this issue.

Differently than mx23, the mx28 reference manual states that ACK_MODE
bit has a default value of 1.

Thanks for pointing this out, as we need to take this into
consideration for supporting mx23 in the mxs i2c driver.


Fabio Estevam

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