| .. SPDX-License-Identifier: GPL-2.0 |
| |
| |
| AMD Sensor Fusion Hub |
| ===================== |
| AMD Sensor Fusion Hub (SFH) is part of an SOC starting from Ryzen-based platforms. |
| The solution is working well on several OEM products. AMD SFH uses HID over PCIe bus. |
| In terms of architecture it resembles ISH, however the major difference is all |
| the HID reports are generated as part of the kernel driver. |
| |
| Block Diagram |
| ------------- |
| |
| :: |
| |
| --------------------------------- |
| | HID User Space Applications | |
| - ------------------------------- |
| |
| --------------------------------------------- |
| --------------------------------- |
| | HID Core | |
| --------------------------------- |
| |
| --------------------------------- |
| | AMD HID Transport | |
| --------------------------------- |
| |
| -------------------------------- |
| | AMD HID Client | |
| | with HID Report Generator| |
| -------------------------------- |
| |
| -------------------------------- |
| | AMD MP2 PCIe Driver | |
| -------------------------------- |
| OS |
| --------------------------------------------- |
| Hardware + Firmware |
| -------------------------------- |
| | SFH MP2 Processor | |
| -------------------------------- |
| |
| |
| AMD HID Transport Layer |
| ----------------------- |
| AMD SFH transport is also implemented as a bus. Each client application executing in the AMD MP2 is |
| registered as a device on this bus. Here, MP2 is an ARM core connected to x86 for processing |
| sensor data. The layer, which binds each device (AMD SFH HID driver) identifies the device type and |
| registers with the HID core. Transport layer attaches a constant "struct hid_ll_driver" object with |
| each device. Once a device is registered with HID core, the callbacks provided via this struct are |
| used by HID core to communicate with the device. AMD HID Transport layer implements the synchronous calls. |
| |
| AMD HID Client Layer |
| -------------------- |
| This layer is responsible to implement HID requests and descriptors. As firmware is OS agnostic, HID |
| client layer fills the HID request structure and descriptors. HID client layer is complex as it is |
| interface between MP2 PCIe layer and HID. HID client layer initializes the MP2 PCIe layer and holds |
| the instance of MP2 layer. It identifies the number of sensors connected using MP2-PCIe layer. Based |
| on that allocates the DRAM address for each and every sensor and passes it to MP2-PCIe driver. On |
| enumeration of each sensor, client layer fills the HID Descriptor structure and HID input report |
| structure. HID Feature report structure is optional. The report descriptor structure varies from |
| sensor to sensor. |
| |
| AMD MP2 PCIe layer |
| ------------------ |
| MP2 PCIe Layer is responsible for making all transactions with the firmware over PCIe. |
| The connection establishment between firmware and PCIe happens here. |
| |
| The communication between X86 and MP2 is split into three parts. |
| 1. Command transfer via the C2P mailbox registers. |
| 2. Data transfer via DRAM. |
| 3. Supported sensor info via P2C registers. |
| |
| Commands are sent to MP2 using C2P Mailbox registers. Writing into C2P Message registers generates |
| interrupt to MP2. The client layer allocates the physical memory and the same is sent to MP2 via |
| the PCI layer. MP2 firmware writes the command output to the access DRAM memory which the client |
| layer has allocated. Firmware always writes minimum of 32 bytes into DRAM. So as a protocol driver |
| shall allocate minimum of 32 bytes DRAM space. |
| |
| Enumeration and Probing flow |
| ---------------------------- |
| :: |
| |
| HID AMD AMD AMD -PCIe MP2 |
| Core Transport Client layer layer FW |
| | | | | | |
| | | | on Boot Driver Loaded | |
| | | | | | |
| | | | MP2-PCIe Int | |
| | | | | | |
| | | |---Get Number of sensors-> | | |
| | | | Read P2C | |
| | | | Register | |
| | | | | | |
| | | | Loop(for No of Sensors) | | |
| | | |----------------------| | | |
| | | | Create HID Descriptor| | | |
| | | | Create Input report | | | |
| | | | Descriptor Map | | | |
| | | | the MP2 FW Index to | | | |
| | | | HID Index | | | |
| | | | Allocate the DRAM | Enable | |
| | | | address | Sensors | |
| | | |----------------------| | | |
| | | HID transport| | Enable | |
| | |<--Probe------| |---Sensor CMD--> | |
| | | Create the | | | |
| | | HID device | | | |
| | | (MFD) | | | |
| | | by Populating| | | |
| | | the HID | | | |
| | | ll_driver | | | |
| | HID | | | | |
| | add | | | | |
| |Device | | | | |
| |<------------- | | | | |
| |
| |
| Data Flow from Application to the AMD SFH Driver |
| ------------------------------------------------ |
| |
| :: |
| |
| | | | | | |
| | | | | | |
| | | | | | |
| | | | | | |
| | | | | | |
| |HID_req | | | | |
| |get_report | | | | |
| |------------->| | | | |
| | | HID_get_input| | | |
| | | report | | | |
| | |------------->|------------------------| | | |
| | | | Read the DRAM data for| | | |
| | | | requested sensor and | | | |
| | | | create the HID input | | | |
| | | | report | | | |
| | | |------------------------| | | |
| | |Data received | | | |
| | | in HID report| | | |
| To |<-------------|<-------------| | | |
| Applications| | | | | |
| <-------| | | | | |
