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| 4 | AMD Sensor Fusion Hub
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| 5 | =====================
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| 6 | AMD Sensor Fusion Hub (SFH) is part of an SOC starting from Ryzen-based platforms.
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| 7 | The solution is working well on several OEM products. AMD SFH uses HID over PCIe bus.
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| 8 | In terms of architecture it resembles ISH, however the major difference is all
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| 9 | the HID reports are generated as part of the kernel driver.
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| 10 |
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| 11 | Block Diagram
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| 12 | -------------
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| 13 |
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| 14 | ::
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| 15 |
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| 16 | ---------------------------------
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| 17 | | HID User Space Applications |
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| 18 | - -------------------------------
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| 19 |
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| 20 | ---------------------------------------------
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| 21 | ---------------------------------
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| 22 | | HID Core |
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| 23 | ---------------------------------
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| 24 |
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| 25 | ---------------------------------
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| 26 | | AMD HID Transport |
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| 27 | ---------------------------------
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| 28 |
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| 29 | --------------------------------
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| 30 | | AMD HID Client |
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| 31 | | with HID Report Generator|
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| 32 | --------------------------------
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| 33 |
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| 34 | --------------------------------
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| 35 | | AMD MP2 PCIe Driver |
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| 36 | --------------------------------
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| 37 | OS
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| 38 | ---------------------------------------------
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| 39 | Hardware + Firmware
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| 40 | --------------------------------
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| 41 | | SFH MP2 Processor |
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| 42 | --------------------------------
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| 43 |
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| 44 |
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| 45 | AMD HID Transport Layer
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| 46 | -----------------------
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| 47 | AMD SFH transport is also implemented as a bus. Each client application executing in the AMD MP2 is
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| 48 | registered as a device on this bus. Here, MP2 is an ARM core connected to x86 for processing
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| 49 | sensor data. The layer, which binds each device (AMD SFH HID driver) identifies the device type and
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| 50 | registers with the HID core. Transport layer attaches a constant "struct hid_ll_driver" object with
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| 51 | each device. Once a device is registered with HID core, the callbacks provided via this struct are
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| 52 | used by HID core to communicate with the device. AMD HID Transport layer implements the synchronous calls.
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| 53 |
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| 54 | AMD HID Client Layer
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| 55 | --------------------
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| 56 | This layer is responsible to implement HID requests and descriptors. As firmware is OS agnostic, HID
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| 57 | client layer fills the HID request structure and descriptors. HID client layer is complex as it is
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| 58 | interface between MP2 PCIe layer and HID. HID client layer initializes the MP2 PCIe layer and holds
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| 59 | the instance of MP2 layer. It identifies the number of sensors connected using MP2-PCIe layer. Based
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| 60 | on that allocates the DRAM address for each and every sensor and passes it to MP2-PCIe driver. On
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| 61 | enumeration of each sensor, client layer fills the HID Descriptor structure and HID input report
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| 62 | structure. HID Feature report structure is optional. The report descriptor structure varies from
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| 63 | sensor to sensor.
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| 64 |
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| 65 | AMD MP2 PCIe layer
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| 66 | ------------------
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| 67 | MP2 PCIe Layer is responsible for making all transactions with the firmware over PCIe.
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| 68 | The connection establishment between firmware and PCIe happens here.
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| 69 |
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| 70 | The communication between X86 and MP2 is split into three parts.
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| 71 | 1. Command transfer via the C2P mailbox registers.
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| 72 | 2. Data transfer via DRAM.
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| 73 | 3. Supported sensor info via P2C registers.
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| 74 |
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| 75 | Commands are sent to MP2 using C2P Mailbox registers. Writing into C2P Message registers generates
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| 76 | interrupt to MP2. The client layer allocates the physical memory and the same is sent to MP2 via
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| 77 | the PCI layer. MP2 firmware writes the command output to the access DRAM memory which the client
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| 78 | layer has allocated. Firmware always writes minimum of 32 bytes into DRAM. So as a protocol driver
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| 79 | shall allocate minimum of 32 bytes DRAM space.
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| 80 |
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| 81 | Enumeration and Probing flow
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| 82 | ----------------------------
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| 83 | ::
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| 84 |
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| 85 | HID AMD AMD AMD -PCIe MP2
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| 86 | Core Transport Client layer layer FW
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| 87 | | | | | |
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| 88 | | | | on Boot Driver Loaded |
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| 89 | | | | | |
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| 90 | | | | MP2-PCIe Int |
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| 91 | | | | | |
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| 92 | | | |---Get Number of sensors-> | |
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| 93 | | | | Read P2C |
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| 94 | | | | Register |
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| 95 | | | | | |
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| 96 | | | | Loop(for No of Sensors) | |
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| 97 | | | |----------------------| | |
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| 98 | | | | Create HID Descriptor| | |
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| 99 | | | | Create Input report | | |
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| 100 | | | | Descriptor Map | | |
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| 101 | | | | the MP2 FW Index to | | |
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| 102 | | | | HID Index | | |
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| 103 | | | | Allocate the DRAM | Enable |
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| 104 | | | | address | Sensors |
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| 105 | | | |----------------------| | |
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| 106 | | | HID transport| | Enable |
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| 107 | | |<--Probe------| |---Sensor CMD--> |
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| 108 | | | Create the | | |
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| 109 | | | HID device | | |
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| 110 | | | (MFD) | | |
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| 111 | | | by Populating| | |
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| 112 | | | the HID | | |
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| 113 | | | ll_driver | | |
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| 114 | | HID | | | |
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| 115 | | add | | | |
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| 116 | |Device | | | |
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| 117 | |<------------- | | | |
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| 118 |
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| 119 |
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| 120 | Data Flow from Application to the AMD SFH Driver
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| 121 | ------------------------------------------------
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| 122 |
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| 123 | ::
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| 124 |
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| 125 | | | | | |
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| 126 | | | | | |
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| 127 | | | | | |
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| 128 | | | | | |
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| 129 | | | | | |
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| 130 | |HID_req | | | |
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| 131 | |get_report | | | |
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| 132 | |------------->| | | |
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| 133 | | | HID_get_input| | |
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| 134 | | | report | | |
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| 135 | | |------------->|------------------------| | |
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| 136 | | | | Read the DRAM data for| | |
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| 137 | | | | requested sensor and | | |
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| 138 | | | | create the HID input | | |
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| 139 | | | | report | | |
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| 140 | | | |------------------------| | |
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| 141 | | |Data received | | |
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| 142 | | | in HID report| | |
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| 143 | To |<-------------|<-------------| | |
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| 144 | Applications| | | | |
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| 145 | <-------| | | | |
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