PolarFire SoC eMMC/SD improvements and RISC-V boot code unification

[dgarske]

PolarFire SoC eMMC/SD improvements and RISC-V boot code unification

Summary

This PR improves the PolarFire SoC (MPFS250) support with eMMC/SD driver stabilization, DMA read support, and fixes a Yocto Linux boot issue. Additionally, it refactors the RISC-V boot code to unify 32-bit and 64-bit architectures into a single codebase.

Changes

PolarFire SoC eMMC/SD Improvements

• Added PLIC (Platform-Level Interrupt Controller) support for handling MMC interrupts
• Implemented DMA read support for SD card operations (significant performance improvement)
• Improved driver stability and timeout handling
• Added MMC interrupt handler with proper interrupt claim/complete flow

RISC-V Boot Code Refactoring

• Unified 32-bit and 64-bit boot code into single files using __riscv_xlen conditional compilation:
  • src/boot_riscv.c (removed boot_riscv64.c)
  • src/boot_riscv_start.S (removed boot_riscv64_start.S)
  • src/vector_riscv.S (removed vector_riscv64.S)
• Created new hal/riscv.h header with common RISC-V definitions (CSRs, register sizes, trap handling macros)

Yocto Linux Boot Fix

• Fixed SMP boot issue where hartid wasn't being properly passed to the Linux kernel
• Implemented proper kernel boot protocol per RISC-V Linux documentation:
  • a0 = hartid of the boot core
  • a1 = physical address of the device tree blob (DTB)
  • satp = 0 (MMU disabled)
• The hartid is now preserved from the prior boot stage (HSS) via the tp register

Documentation

• Updated PolarFire example boot output with timing information
• Updated TODO list (DMA read and timeout handling now complete)

Files Changed

File	Change
hal/mpfs250.c	PLIC and DMA support for eMMC/SD
hal/mpfs250.h	New PLIC and interrupt definitions
hal/riscv.h	New - Common RISC-V definitions
src/boot_riscv.c	Unified 32/64-bit boot with hartid fix
src/boot_riscv_start.S	Unified startup code (renamed from boot_riscv64_start.S)
src/vector_riscv.S	Unified vector table with xlen-aware macros
src/boot_riscv64.c	Removed
src/vector_riscv64.S	Removed
src/update_disk.c	Minor fixes
src/x86/common.c	Related timing improvements
include/hal.h	New HAL function declarations
arch.mk	Build system updates for unified RISC-V files
docs/Targets.md	Updated example output and TODO

Testing

• Tested on Microchip PolarFire SoC (MPFS250) with Yocto Linux
• Verified SMP boot with proper hartid handling
• Confirmed DMA read performance improvements