/*
 * From Coreboot file device/oprom/realmode/x86.c
 *
 * Copyright (C) 2007 Advanced Micro Devices, Inc.
 * Copyright (C) 2009-2010 coresystems GmbH
 *
 * SPDX-License-Identifier:     GPL-2.0
 */
#include <common.h>
#include <bios_emul.h>
#include <vbe.h>
#include <linux/linkage.h>
#include <asm/cache.h>
#include <asm/processor.h>
#include <asm/i8259.h>
#include <asm/io.h>
#include <asm/post.h>
#include "bios.h"

/* Interrupt handlers for each interrupt the ROM can call */
static int (*int_handler[256])(void);

/* to have a common register file for interrupt handlers */
X86EMU_sysEnv _X86EMU_env;

asmlinkage void (*realmode_call)(u32 addr, u32 eax, u32 ebx, u32 ecx, u32 edx,
                                 u32 esi, u32 edi);

asmlinkage void (*realmode_interrupt)(u32 intno, u32 eax, u32 ebx, u32 ecx,
                                      u32 edx, u32 esi, u32 edi);

static void setup_realmode_code(void)
{
        memcpy((void *)REALMODE_BASE, &asm_realmode_code,
               asm_realmode_code_size);

        /* Ensure the global pointers are relocated properly. */
        realmode_call = PTR_TO_REAL_MODE(asm_realmode_call);
        realmode_interrupt = PTR_TO_REAL_MODE(__realmode_interrupt);

        debug("Real mode stub @%x: %d bytes\n", REALMODE_BASE,
              asm_realmode_code_size);
}

static void setup_rombios(void)
{
        const char date[] = "06/11/99";
        memcpy((void *)0xffff5, &date, 8);

        const char ident[] = "PCI_ISA";
        memcpy((void *)0xfffd9, &ident, 7);

        /* system model: IBM-AT */
        writeb(0xfc, 0xffffe);
}

static int int_exception_handler(void)
{
        /* compatibility shim */
        struct eregs reg_info = {
                .eax = M.x86.R_EAX,
                .ecx = M.x86.R_ECX,
                .edx = M.x86.R_EDX,
                .ebx = M.x86.R_EBX,
                .esp = M.x86.R_ESP,
                .ebp = M.x86.R_EBP,
                .esi = M.x86.R_ESI,
                .edi = M.x86.R_EDI,
                .vector = M.x86.intno,
                .error_code = 0,
                .eip = M.x86.R_EIP,
                .cs = M.x86.R_CS,
                .eflags = M.x86.R_EFLG
        };
        struct eregs *regs = &reg_info;

        debug("Oops, exception %d while executing option rom\n", regs->vector);
        cpu_hlt();

        return 0;
}

static int int_unknown_handler(void)
{
        debug("Unsupported software interrupt #0x%x eax 0x%x\n",
              M.x86.intno, M.x86.R_EAX);

        return -1;
}

/* setup interrupt handlers for mainboard */
void bios_set_interrupt_handler(int intnum, int (*int_func)(void))
{
        int_handler[intnum] = int_func;
}

static void setup_interrupt_handlers(void)
{
        int i;

        /*
         * The first 16 int_handler functions are not BIOS services,
         * but the CPU-generated exceptions ("hardware interrupts")
         */
        for (i = 0; i < 0x10; i++)
                int_handler[i] = &int_exception_handler;

        /* Mark all other int_handler calls as unknown first */
        for (i = 0x10; i < 0x100; i++) {
                /* Skip if bios_set_interrupt_handler() isn't called first */
                if (int_handler[i])
                        continue;

                 /*
                  * Now set the default functions that are actually needed
                  * to initialize the option roms. The board may override
                  * these with bios_set_interrupt_handler()
                 */
                switch (i) {
                case 0x10:
                        int_handler[0x10] = &int10_handler;
                        break;
                case 0x12:
                        int_handler[0x12] = &int12_handler;
                        break;
                case 0x16:
                        int_handler[0x16] = &int16_handler;
                        break;
                case 0x1a:
                        int_handler[0x1a] = &int1a_handler;
                        break;
                default:
                        int_handler[i] = &int_unknown_handler;
                        break;
                }
        }
}

static void write_idt_stub(void *target, u8 intnum)
{
        unsigned char *codeptr;

        codeptr = (unsigned char *)target;
        memcpy(codeptr, &__idt_handler, __idt_handler_size);
        codeptr[3] = intnum; /* modify int# in the code stub. */
}

static void setup_realmode_idt(void)
{
        struct realmode_idt *idts = NULL;
        int i;

        /*
         * Copy IDT stub code for each interrupt. This might seem wasteful
         * but it is really simple
         */
         for (i = 0; i < 256; i++) {
                idts[i].cs = 0;
                idts[i].offset = 0x1000 + (i * __idt_handler_size);
                write_idt_stub((void *)((u32)idts[i].offset), i);
        }

        /*
         * Many option ROMs use the hard coded interrupt entry points in the
         * system bios. So install them at the known locations.
         */

        /* int42 is the relocated int10 */
        write_idt_stub((void *)0xff065, 0x42);
        /* BIOS Int 11 Handler F000:F84D */
        write_idt_stub((void *)0xff84d, 0x11);
        /* BIOS Int 12 Handler F000:F841 */
        write_idt_stub((void *)0xff841, 0x12);
        /* BIOS Int 13 Handler F000:EC59 */
        write_idt_stub((void *)0xfec59, 0x13);
        /* BIOS Int 14 Handler F000:E739 */
        write_idt_stub((void *)0xfe739, 0x14);
        /* BIOS Int 15 Handler F000:F859 */
        write_idt_stub((void *)0xff859, 0x15);
        /* BIOS Int 16 Handler F000:E82E */
        write_idt_stub((void *)0xfe82e, 0x16);
        /* BIOS Int 17 Handler F000:EFD2 */
        write_idt_stub((void *)0xfefd2, 0x17);
        /* ROM BIOS Int 1A Handler F000:FE6E */
        write_idt_stub((void *)0xffe6e, 0x1a);
}

static u8 vbe_get_mode_info(struct vbe_mode_info *mi)
{
        u16 buffer_seg;
        u16 buffer_adr;
        char *buffer;

        debug("VBE: Getting information about VESA mode %04x\n",
              mi->video_mode);
        buffer = PTR_TO_REAL_MODE(asm_realmode_buffer);
        buffer_seg = (((unsigned long)buffer) >> 4) & 0xff00;
        buffer_adr = ((unsigned long)buffer) & 0xffff;

        realmode_interrupt(0x10, VESA_GET_MODE_INFO, 0x0000, mi->video_mode,
                           0x0000, buffer_seg, buffer_adr);
        memcpy(mi->mode_info_block, buffer, sizeof(struct vbe_mode_info));
        mi->valid = true;

        return 0;
}

static u8 vbe_set_mode(struct vbe_mode_info *mi)
{
        int video_mode = mi->video_mode;

        debug("VBE: Setting VESA mode %#04x\n", video_mode);
        /* request linear framebuffer mode */
        video_mode |= (1 << 14);
        /* don't clear the framebuffer, we do that later */
        video_mode |= (1 << 15);
        realmode_interrupt(0x10, VESA_SET_MODE, video_mode,
                           0x0000, 0x0000, 0x0000, 0x0000);

        return 0;
}

static void vbe_set_graphics(int vesa_mode, struct vbe_mode_info *mode_info)
{
        unsigned char *framebuffer;

        mode_info->video_mode = (1 << 14) | vesa_mode;
        vbe_get_mode_info(mode_info);

        framebuffer = (unsigned char *)mode_info->vesa.phys_base_ptr;
        debug("VBE: resolution:  %dx%d@%d\n",
              le16_to_cpu(mode_info->vesa.x_resolution),
              le16_to_cpu(mode_info->vesa.y_resolution),
              mode_info->vesa.bits_per_pixel);
        debug("VBE: framebuffer: %p\n", framebuffer);
        if (!framebuffer) {
                debug("VBE: Mode does not support linear framebuffer\n");
                return;
        }

        mode_info->video_mode &= 0x3ff;
        vbe_set_mode(mode_info);
}

void bios_run_on_x86(struct udevice *dev, unsigned long addr, int vesa_mode,
                     struct vbe_mode_info *mode_info)
{
        pci_dev_t pcidev = dm_pci_get_bdf(dev);
        u32 num_dev;

        num_dev = PCI_BUS(pcidev) << 8 | PCI_DEV(pcidev) << 3 |
                        PCI_FUNC(pcidev);

        /* Needed to avoid exceptions in some ROMs */
        interrupt_init();

        /* Set up some legacy information in the F segment */
        setup_rombios();

        /* Set up C interrupt handlers */
        setup_interrupt_handlers();

        /* Set up real-mode IDT */
        setup_realmode_idt();

        /* Make sure the code is placed. */
        setup_realmode_code();

        debug("Calling Option ROM at %lx, pci device %#x...", addr, num_dev);

        /* Option ROM entry point is at OPROM start + 3 */
        realmode_call(addr + 0x0003, num_dev, 0xffff, 0x0000, 0xffff, 0x0,
                      0x0);
        debug("done\n");

        if (vesa_mode != -1)
                vbe_set_graphics(vesa_mode, mode_info);
}

asmlinkage int interrupt_handler(u32 intnumber, u32 gsfs, u32 dses,
                                 u32 edi, u32 esi, u32 ebp, u32 esp,
                                 u32 ebx, u32 edx, u32 ecx, u32 eax,
                                 u32 cs_ip, u16 stackflags)
{
        u32 ip;
        u32 cs;
        u32 flags;
        int ret = 0;

        ip = cs_ip & 0xffff;
        cs = cs_ip >> 16;
        flags = stackflags;

#ifdef CONFIG_REALMODE_DEBUG
        debug("oprom: INT# 0x%x\n", intnumber);
        debug("oprom: eax: %08x ebx: %08x ecx: %08x edx: %08x\n",
              eax, ebx, ecx, edx);
        debug("oprom: ebp: %08x esp: %08x edi: %08x esi: %08x\n",
              ebp, esp, edi, esi);
        debug("oprom:  ip: %04x      cs: %04x   flags: %08x\n",
              ip, cs, flags);
        debug("oprom: stackflags = %04x\n", stackflags);
#endif

        /*
         * Fetch arguments from the stack and put them to a place
         * suitable for the interrupt handlers
         */
        M.x86.R_EAX = eax;
        M.x86.R_ECX = ecx;
        M.x86.R_EDX = edx;
        M.x86.R_EBX = ebx;
        M.x86.R_ESP = esp;
        M.x86.R_EBP = ebp;
        M.x86.R_ESI = esi;
        M.x86.R_EDI = edi;
        M.x86.intno = intnumber;
        M.x86.R_EIP = ip;
        M.x86.R_CS = cs;
        M.x86.R_EFLG = flags;

        /* Call the interrupt handler for this interrupt number */
        ret = int_handler[intnumber]();

        /*
         * This code is quite strange...
         *
         * Put registers back on the stack. The assembler code will pop them
         * later. We force (volatile!) changing the values of the parameters
         * of this function. We know that they stay alive on the stack after
         * we leave this function.
         */
        *(volatile u32 *)&eax = M.x86.R_EAX;
        *(volatile u32 *)&ecx = M.x86.R_ECX;
        *(volatile u32 *)&edx = M.x86.R_EDX;
        *(volatile u32 *)&ebx = M.x86.R_EBX;
        *(volatile u32 *)&esi = M.x86.R_ESI;
        *(volatile u32 *)&edi = M.x86.R_EDI;
        flags = M.x86.R_EFLG;

        /* Pass success or error back to our caller via the CARRY flag */
        if (ret) {
                flags &= ~1; /* no error: clear carry */
        } else {
                debug("int%02x call returned error\n", intnumber);
                flags |= 1;  /* error: set carry */
        }
        *(volatile u16 *)&stackflags = flags;

        return ret;
}