boards: Add SiFive HiFive Premier P550 board documentation

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>

content/boards/eic7700-hifive-premier-p550.md

+---
+title: SiFive HiFive Premier P550 (EIC7700)
+---
+
+The [HiFive Premier P550](https://www.sifive.com/boards/hifive-premier-p550)
+Development Board, powered by the ESWIN EIC7700X SoC with a SiFive Quad-Core
+P550 64-bit Out-of-Order CPU cluster.
+
+Specifications:
+
+* CPU ESWIN EIC7700X
+  * Quad Core SiFive P550 64-bit OOO CPU @ 1.4GHz
+
+* System Memory and Storage
+  * On-board 16GB/32GB 64-bit LPDDR5 @ 6400MT/s
+  * On-board 16 MB SPI NOR Flash
+  * On-board 128 GB eMMC 5.1 Flash
+  * Micro SD Card
+  * 2Kbit EEPROM (Manufacturing data)
+
+* Networking
+  * 1x 100 Mbps Ethernet
+  * 2x 1000 Mbps Ethernet
+
+* Internal Connections
+  * 1x 4-lane PCIe Connector (x16 form factor)
+  * 1x 4-Pin SOM Fan Header (PWM Controlled 5V Supply)
+  * 2x 4-Pin System Fan Header (PWM Controlled/12V Supply)
+  * 1x Battery Holder for Real-Time Clock
+  * 1x 24-Pin ATX Power Measurement Header
+  * 1x 40-Pin GPIOS Header
+  * 1x SATA connector
+  * 1x 10-Pin JTAG Header
+  * 1x M.2 Key E Connector (Wi-Fi)
+  * 1x Header (Connected to Mini-DTX Case Front Panel I/O).
+  * 1x Header (Connected to Type-A in front panel)
+  * 1x Header (Connected to Audio Jacks in front panel)
+  * 1x Type-E Connector for Mini-DTX Case Front Panel Type-C connector Support
+
+* External Connections
+  * 1x Micro SD Card in the rear
+  * 2x Gigabit Ethernet RJ45 Connectors in the rear
+  * 1x 10/100Mbps RJ45 Connector in the rear
+  * 1x HDMI Connector in the rear
+  * 2x USB 3.2 Gen1 Type-A Connectors in the rear
+  * 1x Audio Jack connector in the rear
+  * 1x USB Type-C (JTAG/UART over FT4232H) in the rear
+
+* Power
+  * Type 24Pin ATX Power Connector, and Optional DC12V/5A Adaptor
+  * Battery (Not Included) CR1220 3V Lithium Coin Cell
+
+* Cooling
+  * 1x Pre-Installed Heatsink with Fan
+  * 2x 4-Pin Header (Supports PWM Control) for Chassis/System Fan (Not Included)
+
+### Power supply
+
+The board is be powered with a DC12V/5A Power supply via a 24Pin ATX Power
+Connector.
+
+### Serial consoles
+
+The board has two serial (115200 8N1) console connections available:
+
+* SOM: through the USB Type-C connector on the board, connect a USB type-A to
+  USB type-C cable.
+* MCU: through the top USB Type-A connector on the board, connect a USB type-A
+  to USB type-A cable.
+
+![SiFive HiFive Premier P550 connectors](/img/eic7700-hifive-premier-p550.png)
+
+### MCU - BMC
+
+The P550 MCU (MicroController Unit) acts as a BMC (Baseboard Manager
+Controller), which can be used (among other functions) to control:
+
+* SOM (System On Module) power on/off
+* get/set the boot selection of the SOM
+
+These functions can be controlled through the serial terminal interface of the
+MCU.
+
+#### Bootloader
+
+In the case the bootloader is broken, the following procedure can be followed to
+upload and run a bootloader binary from memory.
+
+Download the latest bootloader binary artifacts from
+https://gitlab.collabora.com/lava/sifive-hifive-p550-boot
+
+Connect to the MCU console and run these steps:
+
+* Turn off the SOM:
+
+```
+#cmd: sompower-s 0
+```
+
+* Set software bootsel configuration:
+
+```
+#cmd: bootsel-s sw 0x3
+Set: Bootsel Controlled by: SW, bootsel[3 2 1 0]:0 0 1 1
+```
+
+* Turn on the SOM:
+
+```
+#cmd: sompower-s 1
+```
+
+Once the board is powered ON with the boot selection set to `0011`, the board
+will enumerate its internal memory as an external USB drive to the host:
+
+```
+[1590796.769517] usb-storage 3-2.2.1:1.0: USB Mass Storage device detected
+[1590796.770002] scsi host11: usb-storage 3-2.2.1:1.0
+[1590797.778142] scsi 11:0:0:0: Direct-Access     ESWIN    WIN-2030              PQ: 0 ANSI: 2
+```
+
+On the host, mount the USB Mass Storage block device (e.g. `/dev/sdb`) and copy
+the bootloader binary file:
+
+```
+$ mount /dev/sdb /mnt
+$ cp bootloader_ddr5_secboot.bin /mnt
+$ umount /mnt 
+```
+
+The P550 board will upload and run the bootloader from memory. On the SOM
+console, bootloader output should be available:
+
+```
+[...]
+U-Boot 2024.01-dirty (Apr 09 2025 - 19:16:14 +0000)
+
+CPU:   rv64imafdc_zba_zbb
+Model: SiFive HiFive Premier P550
+DRAM:  32 GiB (effective 16 GiB)
+[...]
+```
+
+At this point, the uploaded u-boot can be used to flash the rest of the images
+to both the board SPI flash and eMMC memories.
+
+Finally, the board needs to be reset to the default (hardware driven) bootsel
+configuration. In the MCU console, run:
+
+```
+#cmd: bootsel-s hw 0x0
+Set: Bootsel Controlled by: HW, bootsel[3 2 1 0]:0 0 1 0
+```
+
+### Network
+
+Currently unsupported upstream.