Am 27.09.2016 um 19:25 schrieb Stefan Wahren:

quoted

Noralf Tr?nnes [off-list ref] hat am 27. September 2016 um 13:57
geschrieben:


i2c2 is connected to the HDMI connector and is controlled by the
firmware. Disable it to stay out of harms way.

Until this point the commit message is okay, the rest is more confusing.

Btw this should avoid a warning about missing clock frequency.

quoted

From the downstream commit:
i2c-bcm2708/BCM270X_DT: Add support for I2C2

The third I2C bus (I2C2) is normally reserved for HDMI use. Careless
use of this bus can break an attached display - use with caution.

It is recommended to disable accesses by VideoCore by setting
hdmi_ignore_edid=1 or hdmi_edid_file=1 in config.txt.

Signed-off-by: Noralf Tr?nnes <redacted>
---
 arch/arm/boot/dts/bcm2835-rpi.dtsi | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/arm/boot/dts/bcm2835-rpi.dtsi

b/arch/arm/boot/dts/bcm2835-rpi.dtsi
index e9b47b2..8bffbee 100644

--- a/arch/arm/boot/dts/bcm2835-rpi.dtsi
+++ b/arch/arm/boot/dts/bcm2835-rpi.dtsi

@@ -59,10 +59,6 @@
 	clock-frequency = <100000>;
 };
 
-&i2c2 {
-	status = "okay";
-};
-

I'm not sure if this the right fix. According to bcm283x.dtsi the 3 i2c busses
have the same compatible string "brcm,bcm2835-i2c", but the changelog suggests
that this bus is "special".

Shouldn't we use a different compatible string? Our intention isn't to disable
i2c2 but avoid any claims of the usual i2c driver.

i2c2 should not be generally disabled.

There's dtparam=i2c2_iknowwhatimdoing which enables CPU access to this
bus. It's useful for reading out the monitor EDID by the CPU, and for
accessing controls (backlight, volume) on certain monitors.

And I have a I2C touchscreen controller on HDMI DDC.

quoted

 &sdhci {
 	status = "okay";
 	bus-width = <4>;
-- 
2.8.2


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