// SPDX-License-Identifier: GPL-2.0-only
/*
 * MTD map driver for BIOS Flash on Intel SCB2 boards
 * Copyright (C) 2002 Sun Microsystems, Inc.
 * Tim Hockin <thockin@sun.com>
 *
 * A few notes on this MTD map:
 *
 * This was developed with a small number of SCB2 boards to test on.
 * Hopefully, Intel has not introducted too many unaccounted variables in the
 * making of this board.
 *
 * The BIOS marks its own memory region as 'reserved' in the e820 map.  We
 * try to request it here, but if it fails, we carry on anyway.
 *
 * This is how the chip is attached, so said the schematic:
 * * a 4 MiB (32 Mib) 16 bit chip
 * * a 1 MiB memory region
 * * A20 and A21 pulled up
 * * D8-D15 ignored
 * What this means is that, while we are addressing bytes linearly, we are
 * really addressing words, and discarding the other byte.  This means that
 * the chip MUST BE at least 2 MiB.  This also means that every block is
 * actually half as big as the chip reports.  It also means that accesses of
 * logical address 0 hit higher-address sections of the chip, not physical 0.
 * One can only hope that these 4MiB x16 chips were a lot cheaper than 1MiB x8
 * chips.
 *
 * This driver assumes the chip is not write-protected by an external signal.
 * As of the this writing, that is true, but may change, just to spite me.
 *
 * The actual BIOS layout has been mostly reverse engineered.  Intel BIOS
 * updates for this board include 10 related (*.bio - &.bi9) binary files and
 * another separate (*.bbo) binary file.  The 10 files are 64k of data + a
 * small header.  If the headers are stripped off, the 10 64k files can be
 * concatenated into a 640k image.  This is your BIOS image, proper.  The
 * separate .bbo file also has a small header.  It is the 'Boot Block'
 * recovery BIOS.  Once the header is stripped, no further prep is needed.
 * As best I can tell, the BIOS is arranged as such:
 * offset 0x00000 to 0x4ffff (320k):  unknown - SCSI BIOS, etc?
 * offset 0x50000 to 0xeffff (640k):  BIOS proper
 * offset 0xf0000 ty 0xfffff (64k):   Boot Block region
 *
 * Intel's BIOS update program flashes the BIOS and Boot Block in separate
 * steps.  Probably a wise thing to do.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <asm/io.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/map.h>
#include <linux/mtd/cfi.h>
#include <linux/pci.h>
#include <linux/pci_ids.h>

#define MODNAME         "scb2_flash"
#define SCB2_ADDR       0xfff00000
#define SCB2_WINDOW     0x00100000


static void __iomem *scb2_ioaddr;
static struct mtd_info *scb2_mtd;
static struct map_info scb2_map = {
        .name =      "SCB2 BIOS Flash",
        .size =      0,
        .bankwidth =  1,
};
static int region_fail;

static int scb2_fixup_mtd(struct mtd_info *mtd)
{
        int i;
        int done = 0;
        struct map_info *map = mtd->priv;
        struct cfi_private *cfi = map->fldrv_priv;

        /* barf if this doesn't look right */
        if (cfi->cfiq->InterfaceDesc != CFI_INTERFACE_X16_ASYNC) {
                printk(KERN_ERR MODNAME ": unsupported InterfaceDesc: %#x\n",
                    cfi->cfiq->InterfaceDesc);
                return -1;
        }

        /* I wasn't here. I didn't see. dwmw2. */

        /* the chip is sometimes bigger than the map - what a waste */
        mtd->size = map->size;

        /*
         * We only REALLY get half the chip, due to the way it is
         * wired up - D8-D15 are tossed away.  We read linear bytes,
         * but in reality we are getting 1/2 of each 16-bit read,
         * which LOOKS linear to us.  Because CFI code accounts for
         * things like lock/unlock/erase by eraseregions, we need to
         * fudge them to reflect this.  Erases go like this:
         *   * send an erase to an address
         *   * the chip samples the address and erases the block
         *   * add the block erasesize to the address and repeat
         *   -- the problem is that addresses are 16-bit addressable
         *   -- we end up erasing every-other block
         */
        mtd->erasesize /= 2;
        for (i = 0; i < mtd->numeraseregions; i++) {
                struct mtd_erase_region_info *region = &mtd->eraseregions[i];
                region->erasesize /= 2;
        }

        /*
         * If the chip is bigger than the map, it is wired with the high
         * address lines pulled up.  This makes us access the top portion of
         * the chip, so all our erase-region info is wrong.  Start cutting from
         * the bottom.
         */
        for (i = 0; !done && i < mtd->numeraseregions; i++) {
                struct mtd_erase_region_info *region = &mtd->eraseregions[i];

                if (region->numblocks * region->erasesize > mtd->size) {
                        region->numblocks = ((unsigned long)mtd->size /
                                                region->erasesize);
                        done = 1;
                } else {
                        region->numblocks = 0;
                }
                region->offset = 0;
        }

        return 0;
}

/* CSB5's 'Function Control Register' has bits for decoding @ >= 0xffc00000 */
#define CSB5_FCR        0x41
#define CSB5_FCR_DECODE_ALL 0x0e
static int scb2_flash_probe(struct pci_dev *dev,
                            const struct pci_device_id *ent)
{
        u8 reg;

        /* enable decoding of the flash region in the south bridge */
        pci_read_config_byte(dev, CSB5_FCR, &reg);
        pci_write_config_byte(dev, CSB5_FCR, reg | CSB5_FCR_DECODE_ALL);

        if (!request_mem_region(SCB2_ADDR, SCB2_WINDOW, scb2_map.name)) {
                /*
                 * The BIOS seems to mark the flash region as 'reserved'
                 * in the e820 map.  Warn and go about our business.
                 */
                printk(KERN_WARNING MODNAME
                    ": warning - can't reserve rom window, continuing\n");
                region_fail = 1;
        }

        /* remap the IO window (w/o caching) */
        scb2_ioaddr = ioremap(SCB2_ADDR, SCB2_WINDOW);
        if (!scb2_ioaddr) {
                printk(KERN_ERR MODNAME ": Failed to ioremap window!\n");
                if (!region_fail)
                        release_mem_region(SCB2_ADDR, SCB2_WINDOW);
                return -ENOMEM;
        }

        scb2_map.phys = SCB2_ADDR;
        scb2_map.virt = scb2_ioaddr;
        scb2_map.size = SCB2_WINDOW;

        simple_map_init(&scb2_map);

        /* try to find a chip */
        scb2_mtd = do_map_probe("cfi_probe", &scb2_map);

        if (!scb2_mtd) {
                printk(KERN_ERR MODNAME ": flash probe failed!\n");
                iounmap(scb2_ioaddr);
                if (!region_fail)
                        release_mem_region(SCB2_ADDR, SCB2_WINDOW);
                return -ENODEV;
        }

        scb2_mtd->owner = THIS_MODULE;
        if (scb2_fixup_mtd(scb2_mtd) < 0) {
                mtd_device_unregister(scb2_mtd);
                map_destroy(scb2_mtd);
                iounmap(scb2_ioaddr);
                if (!region_fail)
                        release_mem_region(SCB2_ADDR, SCB2_WINDOW);
                return -ENODEV;
        }

        printk(KERN_NOTICE MODNAME ": chip size 0x%llx at offset 0x%llx\n",
               (unsigned long long)scb2_mtd->size,
               (unsigned long long)(SCB2_WINDOW - scb2_mtd->size));

        mtd_device_register(scb2_mtd, NULL, 0);

        return 0;
}

static void scb2_flash_remove(struct pci_dev *dev)
{
        if (!scb2_mtd)
                return;

        /* disable flash writes */
        mtd_lock(scb2_mtd, 0, scb2_mtd->size);

        mtd_device_unregister(scb2_mtd);
        map_destroy(scb2_mtd);

        iounmap(scb2_ioaddr);
        scb2_ioaddr = NULL;

        if (!region_fail)
                release_mem_region(SCB2_ADDR, SCB2_WINDOW);
}

static struct pci_device_id scb2_flash_pci_ids[] = {
        { PCI_DEVICE(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_CSB5) },
        { }
};

static struct pci_driver scb2_flash_driver = {
        .name =     "Intel SCB2 BIOS Flash",
        .id_table = scb2_flash_pci_ids,
        .probe =    scb2_flash_probe,
        .remove =   scb2_flash_remove,
};

module_pci_driver(scb2_flash_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Tim Hockin <thockin@sun.com>");
MODULE_DESCRIPTION("MTD map driver for Intel SCB2 BIOS Flash");
MODULE_DEVICE_TABLE(pci, scb2_flash_pci_ids);