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Diffstat (limited to 'Documentation/devicetree/bindings/dma/qcom_hidma_mgmt.txt')
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diff --git a/Documentation/devicetree/bindings/dma/qcom_hidma_mgmt.txt b/Documentation/devicetree/bindings/dma/qcom_hidma_mgmt.txt new file mode 100644 index 000000000000..fd5618bd8fbc --- /dev/null +++ b/Documentation/devicetree/bindings/dma/qcom_hidma_mgmt.txt @@ -0,0 +1,89 @@ +Qualcomm Technologies HIDMA Management interface + +Qualcomm Technologies HIDMA is a high speed DMA device. It only supports +memcpy and memset capabilities. It has been designed for virtualized +environments. + +Each HIDMA HW instance consists of multiple DMA channels. These channels +share the same bandwidth. The bandwidth utilization can be parititioned +among channels based on the priority and weight assignments. + +There are only two priority levels and 15 weigh assignments possible. + +Other parameters here determine how much of the system bus this HIDMA +instance can use like maximum read/write request and and number of bytes to +read/write in a single burst. + +Main node required properties: +- compatible: "qcom,hidma-mgmt-1.0"; +- reg: Address range for DMA device +- dma-channels: Number of channels supported by this DMA controller. +- max-write-burst-bytes: Maximum write burst in bytes that HIDMA can + occupy the bus for in a single transaction. A memcpy requested is + fragmented to multiples of this amount. This parameter is used while + writing into destination memory. Setting this value incorrectly can + starve other peripherals in the system. +- max-read-burst-bytes: Maximum read burst in bytes that HIDMA can + occupy the bus for in a single transaction. A memcpy request is + fragmented to multiples of this amount. This parameter is used while + reading the source memory. Setting this value incorrectly can starve + other peripherals in the system. +- max-write-transactions: This value is how many times a write burst is + applied back to back while writing to the destination before yielding + the bus. +- max-read-transactions: This value is how many times a read burst is + applied back to back while reading the source before yielding the bus. +- channel-reset-timeout-cycles: Channel reset timeout in cycles for this SOC. + Once a reset is applied to the HW, HW starts a timer for reset operation + to confirm. If reset is not completed within this time, HW reports reset + failure. + +Sub-nodes: + +HIDMA has one or more DMA channels that are used to move data from one +memory location to another. + +When the OS is not in control of the management interface (i.e. it's a guest), +the channel nodes appear on their own, not under a management node. + +Required properties: +- compatible: must contain "qcom,hidma-1.0" +- reg: Addresses for the transfer and event channel +- interrupts: Should contain the event interrupt +- desc-count: Number of asynchronous requests this channel can handle +- iommus: required a iommu node + +Example: + +Hypervisor OS configuration: + + hidma-mgmt@f9984000 = { + compatible = "qcom,hidma-mgmt-1.0"; + reg = <0xf9984000 0x15000>; + dma-channels = <6>; + max-write-burst-bytes = <1024>; + max-read-burst-bytes = <1024>; + max-write-transactions = <31>; + max-read-transactions = <31>; + channel-reset-timeout-cycles = <0x500>; + + hidma_24: dma-controller@0x5c050000 { + compatible = "qcom,hidma-1.0"; + reg = <0 0x5c050000 0x0 0x1000>, + <0 0x5c0b0000 0x0 0x1000>; + interrupts = <0 389 0>; + desc-count = <10>; + iommus = <&system_mmu>; + }; + }; + +Guest OS configuration: + + hidma_24: dma-controller@0x5c050000 { + compatible = "qcom,hidma-1.0"; + reg = <0 0x5c050000 0x0 0x1000>, + <0 0x5c0b0000 0x0 0x1000>; + interrupts = <0 389 0>; + desc-count = <10>; + iommus = <&system_mmu>; + }; |