PolarFire eMMC Support, SDHCI Driver Refactor and add CUSTOM_ENCRYPT_KEY support

[dgarske]

Summary

This PR adds eMMC support for the PolarFire SoC platform and refactors the SD/eMMC driver code into a reusable generic SDHCI module. Additionally, it introduces support for custom encryption key implementations.

Changes

🆕 New Features

• eMMC Support: Added full eMMC support for PolarFire SoC alongside existing SD card support
• Generic SDHCI Driver: Refactored the Cadence SD Host Controller Interface driver into a standalone, reusable module (src/sdhci.c and include/sdhci.h) that can be used by other platforms
• Custom Encryption Key Support: Added CUSTOM_ENCRYPT_KEY option allowing users to implement their own encryption key storage/retrieval functions

♻️ Refactoring

• Moved ~1600 lines of SD/eMMC driver code from hal/mpfs250.c to the new generic src/sdhci.c
• Reduced platform-specific code in hal/mpfs250.c and hal/mpfs250.h significantly
• Added new RISC-V helper macros to hal/riscv.h

📝 Documentation

• Updated docs/Targets.md with custom encryption key usage instructions
• Added comprehensive CUSTOM_ENCRYPT_KEY documentation to docs/encrypted_partitions.md
• Removed completed TODO item for eMMC support from PolarFire section

New Build Options

Option	Description
DISK_SDCARD=1	Enable SD card support via SDHCI driver
DISK_EMMC=1	Enable eMMC support via SDHCI driver
CUSTOM_ENCRYPT_KEY=1	Use custom encryption key implementation

Files Changed

• src/sdhci.c - New generic SDHCI driver implementation
• include/sdhci.h - New SDHCI driver header with full register definitions
• hal/mpfs250.c - Simplified to use the new generic SDHCI driver
• hal/mpfs250.h - Reduced to platform-specific definitions only
• hal/riscv.h - Added RISC-V specific helper macros
• src/boot_riscv.c - Updated for eMMC boot support
• src/update_disk.c - Enhanced disk update logic
• src/libwolfboot.c - Conditional compilation for custom encryption keys
• options.mk - Added new build options
• config/examples/polarfire_mpfs250.config - Updated with SD/eMMC options
• docs/Targets.md - Updated documentation
• docs/encrypted_partitions.md - Added custom encryption key documentation

Usage Example

To enable eMMC instead of SD card in your config:

DISK_SDCARD=0
DISK_EMMC=1

To use custom encryption key storage:

CUSTOM_ENCRYPT_KEY=1
OBJS_EXTRA=src/my_custom_encrypt_key.o

Then implement wolfBoot_get_encrypt_key() in your custom source file.

Testing

• ✅ eMMC support tested on PolarFire SoC hardware
• ✅ SD card support verified to continue working

Example eMMC Encrypted Boot output (with DISK_TEST=1)

wolfBoot Version: 2.7.0 (Dec 31 2025 15:04:41)
Disk encryption enabled
disk_test: Starting tests at block 149504 (buf @ 0x8E000000)
  Test 1: size=128 bytes (1 blocks)... PASS
  Test 2: size=512 bytes (1 blocks)... PASS
  Test 3: size=1024 bytes (2 blocks)... PASS
  Test 4: size=524288 bytes (1024 blocks)... PASS
  Test 5: size=1048576 bytes (2048 blocks)... PASS
disk_test: Complete
Reading MBR...
Found GPT PTE at sector 1
Found valid boot signature in MBR
Valid GPT partition table
Current LBA: 0x1 
Backup LBA: 0xE90E7F 
Max number of partitions: 128
Software limited: only allowing up to 16 partitions per disk.
Disk size: -770916864
disk0.p0 (0_7FFE00h@ 0_100000)
disk0.p1 (0_3FFFE00h@ 0_900000)
disk0.p2 (0_3FFFE00h@ 0_4900000)
disk0.p3 (1_C97FFE00h@ 0_8900000)
Total partitions on disk0: 4
Checking primary OS image in 0,1...
Checking secondary OS image in 0,2...
Versions, A:1 B:0
Load address 0x8E000000
Attempting boot from P:A
Boot partition: 0x801FFD90 (sz 19767004, ver 0x0, type 0x0)
Loading image from disk...done. (1642 ms)
Decrypting image...done. (2894 ms)
Boot partition: 0x8E000000 (sz 19767004, ver 0x0, type 0x0)
Checking image integrity...done. (1507 ms)
Verifying image signature...done. (68 ms)
Firmware Valid.
Flattened uImage Tree: Version 17, Size 19767004
Loading Image kernel-1: 0x8E0002C8 -> 0x80200000 (19745280 bytes)
Image kernel-1: 0x80200000 (19745280 bytes)
Loading Image fdt-1: 0x8F2D4DCC -> 0x8A000000 (19897 bytes)
Image fdt-1: 0x8A000000 (19897 bytes)
Loading DTS: 0x8A000000 -> 0x8A000000 (19897 bytes)
Invalid elf, falling back to raw binary
Booting at 80200000
FDT: Version 17, Size 19897
FDT: Set chosen (13840), bootargs=earlycon root=/dev/mmcblk0p4 rootwait uio_pdrv_genirq.of_id=generic-uio
[    0.000000] Linux version 6.12.22-linux4microchip+fpga-2025.07-g032a7095303a (oe-user@oe-host) (riscv64-oe-linux-gcc (GCC) 13.3.0, GNU ld (GNU Binutils) 2.42.0.20240723) #1 SMP Tue Jul 22 10:04:20 UTC 2025
[    0.000000] Machine model: Microchip PolarFire-SoC VIDEO Kit
[    0.000000] SBI specification v1.0 detected
[    0.000000] SBI implementation ID=0x8 Version=0x10002
[    0.000000] SBI TIME extension detected
[    0.000000] SBI IPI extension detected
[    0.000000] SBI RFENCE extension detected
[    0.000000] SBI SRST extension detected
[    0.000000] earlycon: ns16550a0 at MMIO32 0x0000000020100000 (options '115200n8')
[    0.000000] printk: legacy bootconsole [ns16550a0] enabled

Example SDCARD Encrypted Boot output (with DISK_TEST=1)

wolfBoot Version: 2.7.0 (Dec 31 2025 15:08:00)
Disk encryption enabled
disk_test: Starting tests at block 149504 (buf @ 0x8E000000)
  Test 1: size=128 bytes (1 blocks)... PASS
  Test 2: size=512 bytes (1 blocks)... PASS
  Test 3: size=1024 bytes (2 blocks)... PASS
  Test 4: size=524288 bytes (1024 blocks)... PASS
  Test 5: size=1048576 bytes (2048 blocks)... PASS
disk_test: Complete
Reading MBR...
Found GPT PTE at sector 1
Found valid boot signature in MBR
Valid GPT partition table
Current LBA: 0x1 
Backup LBA: 0x3B723FF 
Max number of partitions: 128
Software limited: only allowing up to 16 partitions per disk.
Disk size: 1849146880
disk0.p0 (0_7FFE00h@ 0_100000)
disk0.p1 (0_3FFFE00h@ 0_900000)
disk0.p2 (0_3FFFE00h@ 0_4900000)
disk0.p3 (7_65AFFE00h@ 0_8900000)
Total partitions on disk0: 4
Checking primary OS image in 0,1...
Checking secondary OS image in 0,2...
Versions, A:1 B:0
Load address 0x8E000000
Attempting boot from P:A
Boot partition: 0x801FFD90 (sz 19767004, ver 0x0, type 0x0)
Loading image from disk...done. (879 ms)
Decrypting image...done. (2894 ms)
Boot partition: 0x8E000000 (sz 19767004, ver 0x0, type 0x0)
Checking image integrity...done. (1507 ms)
Verifying image signature...done. (68 ms)
Firmware Valid.
Flattened uImage Tree: Version 17, Size 19767004
Loading Image kernel-1: 0x8E0002C8 -> 0x80200000 (19745280 bytes)
Image kernel-1: 0x80200000 (19745280 bytes)
Loading Image fdt-1: 0x8F2D4DCC -> 0x8A000000 (19897 bytes)
Image fdt-1: 0x8A000000 (19897 bytes)
Loading DTS: 0x8A000000 -> 0x8A000000 (19897 bytes)
Invalid elf, falling back to raw binary
Booting at 80200000
FDT: Version 17, Size 19897
FDT: Set chosen (13840), bootargs=earlycon root=/dev/mmcblk0p4 rootwait uio_pdrv_genirq.of_id=generic-uio
[    0.000000] Linux version 6.12.22-linux4microchip+fpga-2025.07-g032a7095303a (oe-user@oe-host) (riscv64-oe-linux-gcc (GCC) 13.3.0, GNU ld (GNU Binutils) 2.42.0.20240723) #1 SMP Tue Jul 22 10:04:20 UTC 2025
[    0.000000] Machine model: Microchip PolarFire-SoC VIDEO Kit
[    0.000000] SBI specification v1.0 detected
[    0.000000] SBI implementation ID=0x8 Version=0x10002
[    0.000000] SBI TIME extension detected
[    0.000000] SBI IPI extension detected
[    0.000000] SBI RFENCE extension detected
[    0.000000] SBI SRST extension detected
[    0.000000] earlycon: ns16550a0 at MMIO32 0x0000000020100000 (options '115200n8')
[    0.000000] printk: legacy bootconsole [ns16550a0] enabled

[dgarske]

@danielinux Please don’t merge yet. I need to do a bit more testing with custom encryption key with update_disk loader. The SD card driver changes are good to merge, but the customer doesn’t need them for testing.