[PATCH v6 1/4] SFH: Add maintainers and documentation for AMD SFH based on HID framework

[Sandeep Singh]

From: Sandeep Singh <sandeep.singh@xxxxxxx>

Add Maintainers for AMD SFH(SENSOR FUSION HUB) Solution and work flow
document.

Signed-off-by: Nehal Shah <Nehal-bakulchandra.Shah@xxxxxxx>
Signed-off-by: Sandeep Singh <sandeep.singh@xxxxxxx>
---
 Documentation/hid/amd-sfh-hid.rst | 153 ++++++++++++++++++++++++++++++
 MAINTAINERS                       |   8 ++
 2 files changed, 161 insertions(+)
 create mode 100644 Documentation/hid/amd-sfh-hid.rst

diff --git a/Documentation/hid/amd-sfh-hid.rst b/Documentation/hid/amd-sfh-hid.rst
new file mode 100644
index 000000000000..0ee9003013f2
--- /dev/null
+++ b/Documentation/hid/amd-sfh-hid.rst
@@ -0,0 +1,153 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+AMD Sensor Fusion Hub:-
+======================
+AMD Sensor Fusion Hub is part of a 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 kernel driver.
+
+Block Diagram:-
+=============
+	-------------------------------
+	|  HID User Space Applications  |
+	-------------------------------
+---------------------------------------------
+	 ---------------------------------
+	|		HID Core          |
+	 ---------------------------------
+
+	 ---------------------------------
+	|     AMD HID Transport           |
+	 ---------------------------------
+
+	 --------------------------------
+	|             AMD HID Client     |
+	|	with HID Report Generator|
+	 --------------------------------
+
+	 --------------------------------
+	|     AMD MP2 PCIe Driver         |
+	 --------------------------------
+---------------------------------------------
+	  -------------------------------
+	|     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. MP2 which is an ARM® Cortex-M4 core based co-processor to
+x86. The driver, which binds each device (AMD SFH HID driver) identifies the device type and
+registers with the hid core. Transport drivers attach 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 driver implements the synchronouscalls.
+
+AMD HID Client Layer:-
+**********************
+This layer is responsible to implement HID request and descriptors. As firmware is OS agnostic,
+HID client layer fills the HID request structure and descriptors. HID client layer is in complex
+in nature as it is interface between MP2 PCIe driver and HID. HID client layer initialized
+the MP2 PCIe driver and holds the instance of MP2 driver.It identified the number of sensors
+connected using MP2-PCIe driver and based on that allocate the DRAM address for each and every
+sensor and pass it to MP2-PCIe driver.On enumeration of each sensor, client layer fills out the HID
+Descriptor structure and HID input report structure. HID Feature report structure can be optional.
+The report descriptor structure varies sensor to sensor. Now on enumeration client layer does
+two major things
+1.	Register the HID sensor client to virtual bus (Platform driver) and bind it.
+2.	Probes the AMD HID transport driver. Which in turns register device to the core.
+
+AMD MP2 PCIe layer:-
+********************
+MP2 PCIe Layer is responsible for making all transaction with the firmware over PCIe.
+The connection establishment between firmware and PCIe happens here.
+
+The communication between X86 and MP2 is spilt into three parts.
+1. Command Transfer => C2P Mailbox Register are used
+2. Data Transfer => DRAM
+3. Supported sensor info => P2C Register
+
+Commands are sent to MP2 using C2P Mail Box registers. These C2P  registers are common between x86
+and MP2. Writing into C2P Message register generate interrupt to MP2.  The client layer allocates
+the physical memory and send the same to MP2 for data transfer. MP2 firmware uses HUBIF interface
+to access DRAM memory. For Firmware always write minimum 32 bytes into DRAM.So it is expected that
+driver shall allocate minimum 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:-
+*************************************************
+
+	|	       |              |	  	 	          |		    |
+Get   	|	       |	      |			          |                 |
+Input 	|	       |	      |			          |                 |
+Report	|              |              |                           |                 |
+--->  	|              |              |                           |                 |
+	|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           |              |                           |                 |
+<-------|              |              |                           |                 |
+
+
+Data Flow from AMD SFH Driver to Application:-
+**********************************************
+      |		  |               |	            	          |		    |
+      |           |               |------------------------|      |                 |
+      |           |               |Periodically Read       |      |                 |
+      |           |               |the data for all        |      |                 |
+      |           |               |enumerated sensors      |      |                 |
+      |           |               |from the dram and create|      |                 |
+      |           |               | HID Input reports      |      |                 |
+      |           |               |------------------------|      |                 |
+      |           |HID Input      |                               |                 |
+      |           |Input report   |                               |                 |
+   <----submit to Application-----|                               |                 |
+      |           |               |                               |                 |
diff --git a/MAINTAINERS b/MAINTAINERS
index d53db30d1365..fc6a712893fb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -934,6 +934,14 @@ S:	Supported
 F:	arch/arm64/boot/dts/amd/amd-seattle-xgbe*.dtsi
 F:	drivers/net/ethernet/amd/xgbe/
 
+AMD SENSOR FUSION HUB DRIVER
+M:	Nehal Shah <nehal-bakulchandra.shah@xxxxxxx>
+M:	Sandeep Singh <sandeep.singh@xxxxxxx>
+L:	linux-input@xxxxxxxxxxxxxxx
+S:	Maintained
+F:	Documentation/hid/amd-sfh*
+F:	drivers/hid/amd-sfh-hid/
+
 ANALOG DEVICES INC AD5686 DRIVER
 M:	Michael Hennerich <Michael.Hennerich@xxxxxxxxxx>
 L:	linux-pm@xxxxxxxxxxxxxxx
-- 
2.25.1