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Re: [PATCH 6/7] ARM: bcm2835: Add the DDC I2C controller to the device tree.

From	Stephen Warren <swarren@wwwdotorg.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 6/7] ARM: bcm2835: Add the DDC I2C controller to the device tree.
Date	2015-08-15 07:00 +0200
Message-ID	<pXBJw-7QY-7@gated-at.bofh.it> (permalink)
References	<pWP2a-4fa-3@gated-at.bofh.it> <pWP2a-4fa-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 08/12/2015 06:56 PM, Eric Anholt wrote:
> We need to use it for getting video modes over HDMI.

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

> +		i2c2: i2c@7e805000 {
> +			compatible = "brcm,bcm2835-i2c";
> +			reg = <0x7e805000 0x1000>;
> +			interrupts = <2 21>;
> +			clocks = <&clk_i2c>;
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +		};

In an SoC .dtsi file, you'd typically write:

	status = "disabled";

... in all nodes that represent IO controllers that interface to
external HW, so that board DT files can/must explicitly choose to enable
the device if it's actually in use on the board. Some systems might not
have HDMI and hence might not hook up the HDMI_SCL/SDA pads.

BCM2835-ARM-Peripherals.pdf states "Note that the BSC2 master is used
dedicated with the HDMI interface and should not be accessed by user
programs.". Does this imply the Linux kernel shouldn't be touching this
I2C controller; that the VC4 firmware might also be attempting to use
it? I wonder how any such sharing of the HW would work.
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Thread

[PATCH 6/7] ARM: bcm2835: Add the DDC I2C controller to the device tree. Eric Anholt <eric@anholt.net> - 2015-08-13 03:00 +0200
  Re: [PATCH 6/7] ARM: bcm2835: Add the DDC I2C controller to the device  tree. Stephen Warren <swarren@wwwdotorg.org> - 2015-08-15 07:00 +0200
    Re: [PATCH 6/7] ARM: bcm2835: Add the DDC I2C controller to the device tree. Eric Anholt <eric@anholt.net> - 2015-08-17 20:40 +0200

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