292 lines
8.9 KiB
C
292 lines
8.9 KiB
C
/*
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* Copyright (C) 2009 Juergen Beisert, Pengutronix
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*
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* Mostly stolen from the GRUB2 project
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* Copyright (C) 1999,2000,2001,2002,2003,2004,2005,2006,2007,2008 Free Software Foundation, Inc.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*
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*/
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/**
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* @file
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* @brief Media communication layer through the standard 16 bit PC-BIOS
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*
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* This communication driver does all accesses to the boot medium via 16 bit
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* real mode calls into the standard BIOS. Due to this method, its possible
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* to use all the medias to boot from that are supported by the BIOS. This
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* also includes emulated only medias.
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*
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* To be able to call the real mode BIOS, this driver must switch back to
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* real mode for each access. This will slow down the access a little bit, but
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* we are a boot loader here, not an operating system...
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*
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* Note: We need scratch memory for the BIOS communication, because the BIOS
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* can only handle memory below 0xA0000. So we must copy all data between
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* the flat mode buffers and realmode buffers.
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*
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* Note: This driver makes no sense on other architectures than x86.
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*
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* Note: This driver does only support LBA addressing. Currently no CHS!
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*/
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#include <stdio.h>
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#include <linux/types.h>
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#include <init.h>
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#include <driver.h>
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#include <string.h>
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#include <xfuncs.h>
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#include <asm/syslib.h>
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#include <ata.h>
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#include <errno.h>
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/**
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* Sector count handled in one count
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*
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* @todo 127 are always possible, some BIOS manufacturer supports up to 255.
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* Is it's worth to detect Phoenic's restriction?
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*/
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#define SECTORS_AT_ONCE 64
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/** Size of one sector in bytes */
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#define SECTOR_SIZE 512
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/** Command to read sectors from media */
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#define BIOS_READ_CMD 0
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/** Command to write sectors to media */
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#define BIOS_WRT_CMD 1
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/**
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* "Disk Address Packet Structure" to be used when calling
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* BIOS's int13, function 0x42/0x43
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*/
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struct DAPS
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{
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uint8_t size; /**< always '16' */
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uint8_t res1; /**< always '0' */
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int8_t count; /**< number of sectors 0...127 */
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uint8_t res2; /**< always '0' */
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uint16_t offset; /**< buffer address: offset */
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uint16_t segment; /**< buffer address: segment */
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uint64_t lba; /**< LBA of the start sector */
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} __attribute__ ((packed));
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/**
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* Collection of data we need to know about the connected drive
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*/
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struct media_access {
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int drive_no; /**< drive number used by the BIOS */
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int is_cdrom; /**< drive is a CDROM e.g. no write support */
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};
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/**
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* Scratch memory for BIOS communication to handle data in chunks of 32 kiB
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*
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* Note: This variable is located in the .bss segment, assuming it is located
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* below 0xA0000. If not, the BIOS is not able to read or store any data
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* from/to it. The variable must also aligned to a 16 byte boundary to easify
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* linear to segment:offset address conversion.
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*/
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static uint8_t scratch_buffer[SECTORS_AT_ONCE * SECTOR_SIZE] __attribute__((aligned(16)));
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/**
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* Communication buffer for the 16 bit int13 BIOS call
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*
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* Note: This variable is located in the .bss segment, assuming it is located
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* below 0xA0000. If not, the BIOS is not able to read or store any data
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* from/to it. The variable must also aligned to a 16 byte boundary to easify
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* linear to segment:offset conversion.
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*/
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static struct DAPS bios_daps __attribute__((aligned(16)));
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/**
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* @param media our data we need to do the access
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* @param cmd Command to forward to the BIOS
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* @param sector_start LBA of the start sector
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* @param sector_count Sector count
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* @param buffer Buffer to read from or write to (in the low memory area)
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* @return 0 on success, anything else on failure
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*/
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static int biosdisk_bios_call(struct media_access *media, int cmd, uint64_t sector_start, unsigned sector_count, void *buffer)
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{
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int rc;
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/* prepare the DAPS for the int13 call */
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bios_daps.size = sizeof(struct DAPS);
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bios_daps.res1 = 0;
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bios_daps.count = sector_count; /* always less than 128! */
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bios_daps.res2 = 0;
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bios_daps.segment = (unsigned long)buffer >> 4;
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bios_daps.offset = (unsigned long)buffer - (unsigned long)(bios_daps.segment << 4);
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bios_daps.lba = sector_start;
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if (cmd == BIOS_READ_CMD)
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rc = bios_disk_rw_int13_extensions(0x42, media->drive_no, &bios_daps);
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else if (cmd == BIOS_WRT_CMD)
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rc = bios_disk_rw_int13_extensions(0x43, media->drive_no, &bios_daps);
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else
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return -1;
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return rc;
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}
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/**
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* Read a chunk of sectors from media
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* @param dev our data we need to do the access
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* @param sector_start Sector's LBA number to start read from
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* @param sector_count Sectors to read
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* @param buffer Buffer to read into
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* @return 0 on success, anything else on failure
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*
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* This routine expects the buffer has the correct size to store all data!
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*/
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static int biosdisk_read(struct device_d *dev, uint64_t sector_start, unsigned sector_count, void *buffer)
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{
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int rc;
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struct ata_interface *intf = dev->platform_data;
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struct media_access *media = intf->priv;
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while (sector_count >= SECTORS_AT_ONCE) {
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rc = biosdisk_bios_call(media, BIOS_READ_CMD, sector_start, SECTORS_AT_ONCE, scratch_buffer);
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if (rc != 0)
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return rc;
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__builtin_memcpy(buffer, scratch_buffer, sizeof(scratch_buffer));
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buffer += sizeof(scratch_buffer);
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sector_start += SECTORS_AT_ONCE;
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sector_count -= SECTORS_AT_ONCE;
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};
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/* Are sectors still remaining? */
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if (sector_count) {
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rc = biosdisk_bios_call(media, BIOS_READ_CMD, sector_start, sector_count, scratch_buffer);
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__builtin_memcpy(buffer, scratch_buffer, sector_count * SECTOR_SIZE);
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} else
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rc = 0;
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return rc;
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}
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/**
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* Write a chunk of sectors to media
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* @param dev our data we need to do the access
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* @param sector_start Sector's LBA number to start write to
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* @param sector_count Sectors to write
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* @param buffer Buffer to write from
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* @return 0 on success, anything else on failure
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*
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* This routine expects the buffer has the correct size to read all data!
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*/
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static int biosdisk_write(struct device_d *dev, uint64_t sector_start, unsigned sector_count, const void *buffer)
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{
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int rc;
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struct ata_interface *intf = dev->platform_data;
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struct media_access *media = intf->priv;
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while (sector_count >= SECTORS_AT_ONCE) {
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__builtin_memcpy(scratch_buffer, buffer, sizeof(scratch_buffer));
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rc = biosdisk_bios_call(media, BIOS_WRT_CMD, sector_start, SECTORS_AT_ONCE, scratch_buffer);
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if (rc != 0)
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return rc;
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buffer += sizeof(scratch_buffer);
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sector_start += SECTORS_AT_ONCE;
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sector_count -= SECTORS_AT_ONCE;
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};
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/* Are sectors still remaining? */
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if (sector_count) {
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__builtin_memcpy(scratch_buffer, buffer, sector_count * SECTOR_SIZE);
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rc = biosdisk_bios_call(media, BIOS_WRT_CMD, sector_start, sector_count, scratch_buffer);
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} else
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rc = 0;
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return rc;
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}
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/**
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* Probe for connected drives and register them
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*
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* Detecting if a drive is present is done by simply reading its MBR.
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*
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* FIXME: Relation between BIOS disk numbering scheme and our representation
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* here in barebox (and later on in the linux kernel)
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*/
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static int biosdisk_probe(struct device_d *dev)
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{
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int drive, rc;
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struct media_access media, *m;
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struct device_d *drive_dev;
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struct ata_interface *p;
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for (drive = 0x80; drive < 0x90; drive++) {
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media.drive_no = drive;
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media.is_cdrom = 0; /* don't know yet */
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rc = biosdisk_bios_call(&media, BIOS_READ_CMD, 0, 1, scratch_buffer);
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if (rc != 0)
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continue;
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printf("BIOSdrive %d seems valid. Registering...\n", media.drive_no);
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drive_dev = xzalloc(sizeof(struct device_d) + sizeof(struct media_access) + sizeof(struct ata_interface));
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if (drive_dev == NULL) {
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dev_err(dev, "Out of memory\n");
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return -1;
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}
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m = (struct media_access*)&drive_dev[1];
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p = (struct ata_interface*)&m[1];
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m->drive_no = drive;
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m->is_cdrom = 0;
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p->write = biosdisk_write;
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p->read = biosdisk_read;
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p->priv = m;
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strcpy(drive_dev->name, "biosdisk");
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drive_dev->id = drive - 0x80;
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drive_dev->size = 1;
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drive_dev->map_base = 0;
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drive_dev->platform_data = p;
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register_device(drive_dev);
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}
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return 0;
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}
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static struct driver_d biosdisk_driver = {
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.name = "biosdrive",
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.probe = biosdisk_probe,
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};
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static int biosdisk_init(void)
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{
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/* sanity */
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if (scratch_buffer > (uint8_t*)0x9FFFF) {
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printf("BIOS driver: Scratch memory not in real mode area. Cannot continue!\n");
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return -EIO;
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}
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if (&bios_daps > (struct DAPS*)0x9FFFF) {
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printf("BIOS driver: DAPS memory not in real mode area. Cannot continue!\n");
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return -EIO;
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}
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register_driver(&biosdisk_driver);
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return 0;
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}
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device_initcall(biosdisk_init);
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