[PATCH v7 3/5] ARM: dts: stm32: Add I2C1 support for STM32F429 SoC

 Hi Linus,

2016-12-30 10:07 GMT+01:00 Linus Walleij [off-list ref]:

On Fri, Dec 23, 2016 at 2:09 PM, M'boumba Cedric Madianga
[off-list ref] wrote:

quoted

2016-12-22 20:11 GMT+01:00 Uwe Kleine-K?nig [off-list ref]:

quoted

On Thu, Dec 22, 2016 at 02:35:02PM +0100, M'boumba Cedric Madianga wrote:

quoted

@@ -337,6 +350,16 @@
                                      slew-rate = <2>;
                              };
                      };
+
+                     i2c1_pins_b: i2c1 at 0 {
+                             pins1 {
+                                     pinmux = <STM32F429_PB9_FUNC_I2C1_SDA>;
+                                     drive-open-drain;
+                             };
+                             pins2 {
+                                     pinmux = <STM32F429_PB6_FUNC_I2C1_SCL>;
+                             };

the second doesn't need the open-drain property? Why?

I thought that open-drain was only needed for SDA line.
But after double-checking I2C specification, it seems that SDA and SCL
lines need open-drain or open-collector to perform the wired-AND
function.

I think I2C SDA/SCL must be open drain by definition.

It also requires pull-up resistors, I guess you have these mounted on the board
so you do not need pull-up from the pin controller?

Yes, I have 1 pull-up resistor of 1,5K ohm for each line (SDA & SCL)
on the board

Yours,
Linus Walleij