// SPDX-License-Identifier: GPL-2.0
#include <linux/ioport.h>
#include <linux/printk.h>
#include <asm/e820/api.h>
#include <asm/pci_x86.h>

static void resource_clip(struct resource *res, resource_size_t start,
                          resource_size_t end)
{
        resource_size_t low = 0, high = 0;

        if (res->end < start || res->start > end)
                return;         /* no conflict */

        if (res->start < start)
                low = start - res->start;

        if (res->end > end)
                high = res->end - end;

        /* Keep the area above or below the conflict, whichever is larger */
        if (low > high)
                res->end = start - 1;
        else
                res->start = end + 1;
}

static void remove_e820_regions(struct resource *avail)
{
        int i;
        struct e820_entry *entry;
        u64 e820_start, e820_end;
        struct resource orig = *avail;

        if (!pci_use_e820)
                return;

        for (i = 0; i < e820_table->nr_entries; i++) {
                entry = &e820_table->entries[i];
                e820_start = entry->addr;
                e820_end = entry->addr + entry->size - 1;

                resource_clip(avail, e820_start, e820_end);
                if (orig.start != avail->start || orig.end != avail->end) {
                        pr_info("resource: avoiding allocation from e820 entry [mem %#010Lx-%#010Lx]\n",
                                e820_start, e820_end);
                        if (avail->end > avail->start)
                                /*
                                 * Use %pa instead of %pR because "avail"
                                 * is typically IORESOURCE_UNSET, so %pR
                                 * shows the size instead of addresses.
                                 */
                                pr_info("resource: remaining [mem %pa-%pa] available\n",
                                        &avail->start, &avail->end);
                        orig = *avail;
                }
        }
}

void arch_remove_reservations(struct resource *avail)
{
        /*
         * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
         * the low 1MB unconditionally, as this area is needed for some ISA
         * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
         */
        if (avail->flags & IORESOURCE_MEM) {
                resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);

                remove_e820_regions(avail);
        }
}