diff options
Diffstat (limited to 'drivers/ata/bios.c')
-rw-r--r-- | drivers/ata/bios.c | 291 |
1 files changed, 291 insertions, 0 deletions
diff --git a/drivers/ata/bios.c b/drivers/ata/bios.c new file mode 100644 index 0000000000..51e2425a9d --- /dev/null +++ b/drivers/ata/bios.c @@ -0,0 +1,291 @@ +/* + * Copyright (C) 2009 Juergen Beisert, Pengutronix + * + * Mostly stolen from the GRUB2 project + * Copyright (C) 1999,2000,2001,2002,2003,2004,2005,2006,2007,2008 Free Software Foundation, Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, + * MA 02111-1307 USA + * + */ + +/** + * @file + * @brief Media communication layer through the standard 16 bit PC-BIOS + * + * This communication driver does all accesses to the boot medium via 16 bit + * real mode calls into the standard BIOS. Due to this method, its possible + * to use all the medias to boot from that are supported by the BIOS. This + * also includes emulated only medias. + * + * To be able to call the real mode BIOS, this driver must switch back to + * real mode for each access. This will slow down the access a little bit, but + * we are a boot loader here, not an operating system... + * + * Note: We need scratch memory for the BIOS communication, because the BIOS + * can only handle memory below 0xA0000. So we must copy all data between + * the flat mode buffers and realmode buffers. + * + * Note: This driver makes no sense on other architectures than x86. + * + * Note: This driver does only support LBA addressing. Currently no CHS! + */ + +#include <stdio.h> +#include <linux/types.h> +#include <init.h> +#include <driver.h> +#include <string.h> +#include <xfuncs.h> +#include <asm/syslib.h> +#include <ata.h> +#include <errno.h> + +/** + * Sector count handled in one count + * + * @todo 127 are always possible, some BIOS manufacturer supports up to 255. + * Is it's worth to detect Phoenic's restriction? + */ +#define SECTORS_AT_ONCE 64 + +/** Size of one sector in bytes */ +#define SECTOR_SIZE 512 + +/** Command to read sectors from media */ +#define BIOS_READ_CMD 0 + +/** Command to write sectors to media */ +#define BIOS_WRT_CMD 1 + +/** + * "Disk Address Packet Structure" to be used when calling + * BIOS's int13, function 0x42/0x43 + */ +struct DAPS +{ + uint8_t size; /**< always '16' */ + uint8_t res1; /**< always '0' */ + int8_t count; /**< number of sectors 0...127 */ + uint8_t res2; /**< always '0' */ + uint16_t offset; /**< buffer address: offset */ + uint16_t segment; /**< buffer address: segment */ + uint64_t lba; /**< LBA of the start sector */ +} __attribute__ ((packed)); + +/** + * Collection of data we need to know about the connected drive + */ +struct media_access { + int drive_no; /**< drive number used by the BIOS */ + int is_cdrom; /**< drive is a CDROM e.g. no write support */ +}; + +/** + * Scratch memory for BIOS communication to handle data in chunks of 32 kiB + * + * Note: This variable is located in the .bss segment, assuming it is located + * below 0xA0000. If not, the BIOS is not able to read or store any data + * from/to it. The variable must also aligned to a 16 byte boundary to easify + * linear to segment:offset address conversion. + */ +static uint8_t scratch_buffer[SECTORS_AT_ONCE * SECTOR_SIZE] __attribute__((aligned(16))); + +/** + * Communication buffer for the 16 bit int13 BIOS call + * + * Note: This variable is located in the .bss segment, assuming it is located + * below 0xA0000. If not, the BIOS is not able to read or store any data + * from/to it. The variable must also aligned to a 16 byte boundary to easify + * linear to segment:offset conversion. + */ +static struct DAPS bios_daps __attribute__((aligned(16))); + +/** + * @param media our data we need to do the access + * @param cmd Command to forward to the BIOS + * @param sector_start LBA of the start sector + * @param sector_count Sector count + * @param buffer Buffer to read from or write to (in the low memory area) + * @return 0 on success, anything else on failure + */ +static int biosdisk_bios_call(struct media_access *media, int cmd, uint64_t sector_start, unsigned sector_count, void *buffer) +{ + int rc; + + /* prepare the DAPS for the int13 call */ + bios_daps.size = sizeof(struct DAPS); + bios_daps.res1 = 0; + bios_daps.count = sector_count; /* always less than 128! */ + bios_daps.res2 = 0; + bios_daps.segment = (unsigned long)buffer >> 4; + bios_daps.offset = (unsigned long)buffer - (unsigned long)(bios_daps.segment << 4); + bios_daps.lba = sector_start; + + if (cmd == BIOS_READ_CMD) + rc = bios_disk_rw_int13_extensions(0x42, media->drive_no, &bios_daps); + else if (cmd == BIOS_WRT_CMD) + rc = bios_disk_rw_int13_extensions(0x43, media->drive_no, &bios_daps); + else + return -1; + + return rc; +} + +/** + * Read a chunk of sectors from media + * @param dev our data we need to do the access + * @param sector_start Sector's LBA number to start read from + * @param sector_count Sectors to read + * @param buffer Buffer to read into + * @return 0 on success, anything else on failure + * + * This routine expects the buffer has the correct size to store all data! + */ +static int biosdisk_read(struct device_d *dev, uint64_t sector_start, unsigned sector_count, void *buffer) +{ + int rc; + struct ata_interface *intf = dev->platform_data; + struct media_access *media = intf->priv; + + while (sector_count >= SECTORS_AT_ONCE) { + rc = biosdisk_bios_call(media, BIOS_READ_CMD, sector_start, SECTORS_AT_ONCE, scratch_buffer); + if (rc != 0) + return rc; + __builtin_memcpy(buffer, scratch_buffer, sizeof(scratch_buffer)); + buffer += sizeof(scratch_buffer); + sector_start += SECTORS_AT_ONCE; + sector_count -= SECTORS_AT_ONCE; + }; + + /* Are sectors still remaining? */ + if (sector_count) { + rc = biosdisk_bios_call(media, BIOS_READ_CMD, sector_start, sector_count, scratch_buffer); + __builtin_memcpy(buffer, scratch_buffer, sector_count * SECTOR_SIZE); + } else + rc = 0; + + return rc; +} + +/** + * Write a chunk of sectors to media + * @param dev our data we need to do the access + * @param sector_start Sector's LBA number to start write to + * @param sector_count Sectors to write + * @param buffer Buffer to write from + * @return 0 on success, anything else on failure + * + * This routine expects the buffer has the correct size to read all data! + */ +static int biosdisk_write(struct device_d *dev, uint64_t sector_start, unsigned sector_count, const void *buffer) +{ + int rc; + struct ata_interface *intf = dev->platform_data; + struct media_access *media = intf->priv; + + while (sector_count >= SECTORS_AT_ONCE) { + __builtin_memcpy(scratch_buffer, buffer, sizeof(scratch_buffer)); + rc = biosdisk_bios_call(media, BIOS_WRT_CMD, sector_start, SECTORS_AT_ONCE, scratch_buffer); + if (rc != 0) + return rc; + buffer += sizeof(scratch_buffer); + sector_start += SECTORS_AT_ONCE; + sector_count -= SECTORS_AT_ONCE; + }; + + /* Are sectors still remaining? */ + if (sector_count) { + __builtin_memcpy(scratch_buffer, buffer, sector_count * SECTOR_SIZE); + rc = biosdisk_bios_call(media, BIOS_WRT_CMD, sector_start, sector_count, scratch_buffer); + } else + rc = 0; + + return rc; +} + +/** + * Probe for connected drives and register them + * + * Detecting if a drive is present is done by simply reading its MBR. + * + * FIXME: Relation between BIOS disk numbering scheme and our representation + * here in barebox (and later on in the linux kernel) + */ +static int biosdisk_probe(struct device_d *dev) +{ + int drive, rc; + struct media_access media, *m; + struct device_d *drive_dev; + struct ata_interface *p; + + for (drive = 0x80; drive < 0x90; drive++) { + media.drive_no = drive; + media.is_cdrom = 0; /* don't know yet */ + rc = biosdisk_bios_call(&media, BIOS_READ_CMD, 0, 1, scratch_buffer); + if (rc != 0) + continue; + + printf("BIOSdrive %d seems valid. Registering...\n", media.drive_no); + + drive_dev = xzalloc(sizeof(struct device_d) + sizeof(struct media_access) + sizeof(struct ata_interface)); + if (drive_dev == NULL) { + dev_err(dev, "Out of memory\n"); + return -1; + } + m = (struct media_access*)&drive_dev[1]; + p = (struct ata_interface*)&m[1]; + + m->drive_no = drive; + m->is_cdrom = 0; + + p->write = biosdisk_write; + p->read = biosdisk_read; + p->priv = m; + + strcpy(drive_dev->name, "biosdisk"); + drive_dev->id = drive - 0x80; + drive_dev->size = 1; + drive_dev->map_base = 0; + drive_dev->platform_data = p; + + register_device(drive_dev); + } + + return 0; +} + +static struct driver_d biosdisk_driver = { + .name = "biosdrive", + .probe = biosdisk_probe, +}; + +static int biosdisk_init(void) +{ + /* sanity */ + if (scratch_buffer > (uint8_t*)0x9FFFF) { + printf("BIOS driver: Scratch memory not in real mode area. Cannot continue!\n"); + return -EIO; + } + if (&bios_daps > (struct DAPS*)0x9FFFF) { + printf("BIOS driver: DAPS memory not in real mode area. Cannot continue!\n"); + return -EIO; + } + + register_driver(&biosdisk_driver); + return 0; +} + +device_initcall(biosdisk_init); |