Re: [PATCH v2] i2c: rk3x: fix bug that cause measured high_ns doesn't meet I2C spec

Doug Anderson
2014-12-03T05:13:58Z

Addy,

On Tue, Dec 2, 2014 at 6:37 PM, Addy Ke <addy.ke@rock-chips.com> wrote:
> high_ns calculated from the low division of CLKDIV register is the sum
> of actual measured high_ns and rise_ns. The rise time which related to
> external pull-up resistor can be up to the maximum rise time in I2C spec.
>
> In my test, if external pull-up resistor is 4.7K, rise_ns is about
> 700ns. So the actual measured high_ns is about 3900ns, which is less
> than 4000ns(the minimum high_ns in I2C spec).
>
> To fix this bug, min_low_ns should include fall time and min_high_ns
> should include rise time too.
>
> This patch merged the patch that Doug submitted to chromium, which
> can get the rise and fall times for signals from the device tree.
> This allows us to more accurately calculate timings. see:
> https://chromium-review.googlesource.com/#/c/232774/
>
> Signed-off-by: Addy Ke <addy.ke@rock-chips.com>
> ---
> Changes in v2:
> - merged the patch that Doug submitted to chromium
>
> Documentation/devicetree/bindings/i2c/i2c-rk3x.txt | 10 ++++
> drivers/i2c/busses/i2c-rk3x.c | 55 +++++++++++++++-------
> 2 files changed, 47 insertions(+), 18 deletions(-)

This looks good to me. Thank you for spinning.

Reviewed-by: Doug Anderson <dianders@chromium.org>