LXR linux/drivers/firmware/efi/libstub/riscv-stub.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (C) 2020 Western Digital Corporation or its affiliates.
   4 */
   5
   6#include <linux/efi.h>
   7#include <linux/libfdt.h>
   8
   9#include <asm/efi.h>
  10#include <asm/sections.h>
  11
  12#include "efistub.h"
  13
  14/*
  15 * RISC-V requires the kernel image to placed 2 MB aligned base for 64 bit and
  16 * 4MB for 32 bit.
  17 */
  18#ifdef CONFIG_64BIT
  19#define MIN_KIMG_ALIGN          SZ_2M
  20#else
  21#define MIN_KIMG_ALIGN          SZ_4M
  22#endif
  23
  24typedef void __noreturn (*jump_kernel_func)(unsigned int, unsigned long);
  25
  26static u32 hartid;
  27
  28static u32 get_boot_hartid_from_fdt(void)
  29{
  30        const void *fdt;
  31        int chosen_node, len;
  32        const fdt32_t *prop;
  33
  34        fdt = get_efi_config_table(DEVICE_TREE_GUID);
  35        if (!fdt)
  36                return U32_MAX;
  37
  38        chosen_node = fdt_path_offset(fdt, "/chosen");
  39        if (chosen_node < 0)
  40                return U32_MAX;
  41
  42        prop = fdt_getprop((void *)fdt, chosen_node, "boot-hartid", &len);
  43        if (!prop || len != sizeof(u32))
  44                return U32_MAX;
  45
  46        return fdt32_to_cpu(*prop);
  47}
  48
  49efi_status_t check_platform_features(void)
  50{
  51        hartid = get_boot_hartid_from_fdt();
  52        if (hartid == U32_MAX) {
  53                efi_err("/chosen/boot-hartid missing or invalid!\n");
  54                return EFI_UNSUPPORTED;
  55        }
  56        return EFI_SUCCESS;
  57}
  58
  59void __noreturn efi_enter_kernel(unsigned long entrypoint, unsigned long fdt,
  60                                 unsigned long fdt_size)
  61{
  62        unsigned long stext_offset = _start_kernel - _start;
  63        unsigned long kernel_entry = entrypoint + stext_offset;
  64        jump_kernel_func jump_kernel = (jump_kernel_func)kernel_entry;
  65
  66        /*
  67         * Jump to real kernel here with following constraints.
  68         * 1. MMU should be disabled.
  69         * 2. a0 should contain hartid
  70         * 3. a1 should DT address
  71         */
  72        csr_write(CSR_SATP, 0);
  73        jump_kernel(hartid, fdt);
  74}
  75
  76efi_status_t handle_kernel_image(unsigned long *image_addr,
  77                                 unsigned long *image_size,
  78                                 unsigned long *reserve_addr,
  79                                 unsigned long *reserve_size,
  80                                 efi_loaded_image_t *image)
  81{
  82        unsigned long kernel_size = 0;
  83        unsigned long preferred_addr;
  84        efi_status_t status;
  85
  86        kernel_size = _edata - _start;
  87        *image_addr = (unsigned long)_start;
  88        *image_size = kernel_size + (_end - _edata);
  89
  90        /*
  91         * RISC-V kernel maps PAGE_OFFSET virtual address to the same physical
  92         * address where kernel is booted. That's why kernel should boot from
  93         * as low as possible to avoid wastage of memory. Currently, dram_base
  94         * is occupied by the firmware. So the preferred address for kernel to
  95         * boot is next aligned address. If preferred address is not available,
  96         * relocate_kernel will fall back to efi_low_alloc_above to allocate
  97         * lowest possible memory region as long as the address and size meets
  98         * the alignment constraints.
  99         */
 100        preferred_addr = MIN_KIMG_ALIGN;
 101        status = efi_relocate_kernel(image_addr, kernel_size, *image_size,
 102                                     preferred_addr, MIN_KIMG_ALIGN, 0x0);
 103
 104        if (status != EFI_SUCCESS) {
 105                efi_err("Failed to relocate kernel\n");
 106                *image_size = 0;
 107        }
 108        return status;
 109}
 110