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@@ -51,6 +51,8 @@ Table of Contents
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VIII - Specifying device power management information (sleep property)
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+ IX - Specifying dma bus information
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+
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Appendix A - Sample SOC node for MPC8540
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@@ -1332,6 +1334,57 @@ reasonably grouped in this manner, then create a virtual sleep controller
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(similar to an interrupt nexus, except that defining a standardized
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sleep-map should wait until its necessity is demonstrated).
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+IX - Specifying dma bus information
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+
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+Some devices may have DMA memory range shifted relatively to the beginning of
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+RAM, or even placed outside of kernel RAM. For example, the Keystone 2 SoC
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+worked in LPAE mode with 4G memory has:
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+- RAM range: [0x8 0000 0000, 0x8 FFFF FFFF]
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+- DMA range: [ 0x8000 0000, 0xFFFF FFFF]
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+and DMA range is aliased into first 2G of RAM in HW.
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+
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+In such cases, DMA addresses translation should be performed between CPU phys
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+and DMA addresses. The "dma-ranges" property is intended to be used
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+for describing the configuration of such system in DT.
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+
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+In addition, each DMA master device on the DMA bus may or may not support
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+coherent DMA operations. The "dma-coherent" property is intended to be used
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+for identifying devices supported coherent DMA operations in DT.
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+
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+* DMA Bus master
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+Optional property:
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+- dma-ranges: <prop-encoded-array> encoded as arbitrary number of triplets of
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+ (child-bus-address, parent-bus-address, length). Each triplet specified
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+ describes a contiguous DMA address range.
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+ The dma-ranges property is used to describe the direct memory access (DMA)
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+ structure of a memory-mapped bus whose device tree parent can be accessed
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+ from DMA operations originating from the bus. It provides a means of
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+ defining a mapping or translation between the physical address space of
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+ the bus and the physical address space of the parent of the bus.
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+ (for more information see ePAPR specification)
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+
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+* DMA Bus child
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+Optional property:
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+- dma-ranges: <empty> value. if present - It means that DMA addresses
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+ translation has to be enabled for this device.
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+- dma-coherent: Present if dma operations are coherent
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+
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+Example:
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+soc {
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+ compatible = "ti,keystone","simple-bus";
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+ ranges = <0x0 0x0 0x0 0xc0000000>;
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+ dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>;
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+
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+ [...]
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+
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+ usb: usb@2680000 {
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+ compatible = "ti,keystone-dwc3";
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+
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+ [...]
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+ dma-coherent;
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+ };
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+};
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+
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Appendix A - Sample SOC node for MPC8540
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========================================
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Grant Likely