--- zzzz-none-000/linux-3.10.107/Documentation/devicetree/booting-without-of.txt 2017-06-27 09:49:32.000000000 +0000 +++ scorpion-7490-727/linux-3.10.107/Documentation/devicetree/booting-without-of.txt 2021-02-04 17:41:59.000000000 +0000 @@ -15,6 +15,7 @@ 1) Entry point for arch/arm 2) Entry point for arch/powerpc 3) Entry point for arch/x86 + 4) Entry point for arch/mips/bmips II - The DT block format 1) Header @@ -51,6 +52,8 @@ VIII - Specifying device power management information (sleep property) + IX - Specifying dma bus information + Appendix A - Sample SOC node for MPC8540 @@ -286,6 +289,33 @@ or initrd address. It simply holds information which can not be retrieved otherwise like interrupt routing or a list of devices behind an I2C bus. +4) Entry point for arch/mips/bmips +---------------------------------- + + Some bootloaders only support a single entry point, at the start of the + kernel image. Other bootloaders will jump to the ELF start address. + Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y, + so the first instruction immediately jumps to kernel_entry(). + + Similar to the arch/arm case (b), a DT-aware bootloader is expected to + set up the following registers: + + a0 : 0 + + a1 : 0xffffffff + + a2 : Physical pointer to the device tree block (defined in chapter + II) in RAM. The device tree can be located anywhere in the first + 512MB of the physical address space (0x00000000 - 0x1fffffff), + aligned on a 64 bit boundary. + + Legacy bootloaders do not use this convention, and they do not pass in a + DT block. In this case, Linux will look for a builtin DTB, selected via + CONFIG_DT_*. + + This convention is defined for 32-bit systems only, as there are not + currently any 64-bit BMIPS implementations. + II - The DT block format ======================== @@ -826,6 +856,10 @@ name may clash with standard defined ones, you prefix them with your vendor name and a comma. + Additional properties for the root node: + + - serial-number : a string representing the device's serial number + b) The /cpus node This node is the parent of all individual CPU nodes. It doesn't @@ -1332,6 +1366,57 @@ (similar to an interrupt nexus, except that defining a standardized sleep-map should wait until its necessity is demonstrated). +IX - Specifying dma bus information + +Some devices may have DMA memory range shifted relatively to the beginning of +RAM, or even placed outside of kernel RAM. For example, the Keystone 2 SoC +worked in LPAE mode with 4G memory has: +- RAM range: [0x8 0000 0000, 0x8 FFFF FFFF] +- DMA range: [ 0x8000 0000, 0xFFFF FFFF] +and DMA range is aliased into first 2G of RAM in HW. + +In such cases, DMA addresses translation should be performed between CPU phys +and DMA addresses. The "dma-ranges" property is intended to be used +for describing the configuration of such system in DT. + +In addition, each DMA master device on the DMA bus may or may not support +coherent DMA operations. The "dma-coherent" property is intended to be used +for identifying devices supported coherent DMA operations in DT. + +* DMA Bus master +Optional property: +- dma-ranges: encoded as arbitrary number of triplets of + (child-bus-address, parent-bus-address, length). Each triplet specified + describes a contiguous DMA address range. + The dma-ranges property is used to describe the direct memory access (DMA) + structure of a memory-mapped bus whose device tree parent can be accessed + from DMA operations originating from the bus. It provides a means of + defining a mapping or translation between the physical address space of + the bus and the physical address space of the parent of the bus. + (for more information see ePAPR specification) + +* DMA Bus child +Optional property: +- dma-ranges: value. if present - It means that DMA addresses + translation has to be enabled for this device. +- dma-coherent: Present if dma operations are coherent + +Example: +soc { + compatible = "ti,keystone","simple-bus"; + ranges = <0x0 0x0 0x0 0xc0000000>; + dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>; + + [...] + + usb: usb@2680000 { + compatible = "ti,keystone-dwc3"; + + [...] + dma-coherent; + }; +}; + Appendix A - Sample SOC node for MPC8540 ======================================== @@ -1364,19 +1449,16 @@ phy0: ethernet-phy@0 { interrupts = <5 1>; reg = <0>; - device_type = "ethernet-phy"; }; phy1: ethernet-phy@1 { interrupts = <5 1>; reg = <1>; - device_type = "ethernet-phy"; }; phy3: ethernet-phy@3 { interrupts = <7 1>; reg = <3>; - device_type = "ethernet-phy"; }; }; };