On Mon, 2021-07-12 at 14:53 -0600, Rob Herring wrote:

On Mon, Jun 21, 2021 at 06:39:44PM +0800, kewei.xu@mediatek.com wrote:

quoted

From: Kewei Xu <redacted>

Add attribute default-timing-adjust for DT-binding document.

Fixes: be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust support")

You want to fix a kernel change with a DT change? That's not a 
compatible change (and I guess neither was the kernel change). Sounds 
like the above commit should be reverted and rethink how to add a new 
feature...

quoted

Signed-off-by: Kewei Xu <redacted>
---
 Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt b/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt
index 7c4915bc..7b80a11 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt

@@ -33,6 +33,8 @@ Optional properties:
   - mediatek,have-pmic: platform can control i2c form special pmic side.
     Only mt6589 and mt8135 support this feature.
   - mediatek,use-push-pull: IO config use push-pull mode.
+  - mediatek,default-timing-adjust: use default timing calculation, no timing
+    adjustment.
 
 Example:
 

-- 
1.9.1

Hi Rob,

In the commit be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust
support"), the I2C timing calculation has been revised to support
ac-timing adjustment.But in our design, it will make
tSU,STA/tHD,STA/tSU,STO shorter when the slave device have
clock-stretching feature.
Then we upload the commit a80f24945fcf ("i2c: mediatek: Use
scl_int_delay_ns to compensate clock-stretching") to support adjusting
tSU,STA/tHD,STA/tSU,STO when the slave device clock-stretching. But if
the slave device stretch the SCL line for too long time, our design
still cannot make tSU,STA/tHD,STA/tSU,STO meet spec.
However in the old (default) timing algorithm before the commit
be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust support"),
tSU,STA/tHD,STA/tSU,STO can meet spec. So we want to define a new
setting "default-adjust-timing" for using the old (default) timing
algorithm.

thanks
kewei
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