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fix line reference #246

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fix line reference #246

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2 changes: 1 addition & 1 deletion docs/lesson01/linux/kernel-startup.md
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Expand Up @@ -40,7 +40,7 @@ Next, we can find [bcm2837-rpi-3-b.dts](https://github.com/torvalds/linux/blob/v

As I mentioned previously, `BCM2837` and `BCM2835` have an identical peripheral hardware, and, if you follow the chain of includes, you can find [bcm283x.dtsi](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi) that actually defines most of this hardware.

A device tree definition consists of the blocks nested one in another. At the top level we usually can find such blocks as [cpus](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm2837.dtsi#L30) or [memory](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm2837-rpi-3-b.dts#L17) The meaning of those blocks should be quite self-explanatory. Another interesting top-level element that we can find in the `bcm283x.dtsi` is [SoC](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L52) that means [System on a chip](https://en.wikipedia.org/wiki/System_on_a_chip) It tells us that all peripheral devices are directly mapped to some memory area via memory mapped registers. `soc` element serves as a parent element for all peripheral devices. One of its children is [gpio](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L147) element. This element defines [reg = <0x7e200000 0xb4>](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L149) property that tells us that GPIO memory mapped registers are located in the `[0x7e200000 : 0x7e2000b4]` region. One of the childern of `gpio` element has the [following definition](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L474)
A device tree definition consists of the blocks nested one in another. At the top level we usually can find such blocks as [cpus](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm2837.dtsi#L30) or [memory](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm2837-rpi-3-b.dts#L17) The meaning of those blocks should be quite self-explanatory. Another interesting top-level element that we can find in the `bcm283x.dtsi` is [SoC](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L52) that means [System on a chip](https://en.wikipedia.org/wiki/System_on_a_chip) It tells us that all peripheral devices are directly mapped to some memory area via memory mapped registers. `soc` element serves as a parent element for all peripheral devices. One of its children is [gpio](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L147) element. This element defines [reg = <0x7e200000 0xb4>](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L149) property that tells us that GPIO memory mapped registers are located in the `[0x7e200000 : 0x7e2000b4]` region. One of the childern of `gpio` element has the [following definition](https://github.com/torvalds/linux/blob/v4.14/arch/arm/boot/dts/bcm283x.dtsi#L351)

```
uart1_gpio14: uart1_gpio14 {
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