/*
 * Suspend support specific for s390.
 *
 * Copyright IBM Corp. 2009
 *
 * Author(s): Hans-Joachim Picht <hans@linux.vnet.ibm.com>
 */

#include <linux/pfn.h>
#include <linux/suspend.h>
#include <linux/mm.h>
#include <asm/ctl_reg.h>

/*
 * References to section boundaries
 */
extern const void __nosave_begin, __nosave_end;

/*
 * The restore of the saved pages in an hibernation image will set
 * the change and referenced bits in the storage key for each page.
 * Overindication of the referenced bits after an hibernation cycle
 * does not cause any harm but the overindication of the change bits
 * would cause trouble.
 * Use the ARCH_SAVE_PAGE_KEYS hooks to save the storage key of each
 * page to the most significant byte of the associated page frame
 * number in the hibernation image.
 */

/*
 * Key storage is allocated as a linked list of pages.
 * The size of the keys array is (PAGE_SIZE - sizeof(long))
 */
struct page_key_data {
        struct page_key_data *next;
        unsigned char data[];
};

#define PAGE_KEY_DATA_SIZE      (PAGE_SIZE - sizeof(struct page_key_data *))

static struct page_key_data *page_key_data;
static struct page_key_data *page_key_rp, *page_key_wp;
static unsigned long page_key_rx, page_key_wx;

/*
 * For each page in the hibernation image one additional byte is
 * stored in the most significant byte of the page frame number.
 * On suspend no additional memory is required but on resume the
 * keys need to be memorized until the page data has been restored.
 * Only then can the storage keys be set to their old state.
 */
unsigned long page_key_additional_pages(unsigned long pages)
{
        return DIV_ROUND_UP(pages, PAGE_KEY_DATA_SIZE);
}

/*
 * Free page_key_data list of arrays.
 */
void page_key_free(void)
{
        struct page_key_data *pkd;

        while (page_key_data) {
                pkd = page_key_data;
                page_key_data = pkd->next;
                free_page((unsigned long) pkd);
        }
}

/*
 * Allocate page_key_data list of arrays with enough room to store
 * one byte for each page in the hibernation image.
 */
int page_key_alloc(unsigned long pages)
{
        struct page_key_data *pk;
        unsigned long size;

        size = DIV_ROUND_UP(pages, PAGE_KEY_DATA_SIZE);
        while (size--) {
                pk = (struct page_key_data *) get_zeroed_page(GFP_KERNEL);
                if (!pk) {
                        page_key_free();
                        return -ENOMEM;
                }
                pk->next = page_key_data;
                page_key_data = pk;
        }
        page_key_rp = page_key_wp = page_key_data;
        page_key_rx = page_key_wx = 0;
        return 0;
}

/*
 * Save the storage key into the upper 8 bits of the page frame number.
 */
void page_key_read(unsigned long *pfn)
{
        unsigned long addr;

        addr = (unsigned long) page_address(pfn_to_page(*pfn));
        *(unsigned char *) pfn = (unsigned char) page_get_storage_key(addr);
}

/*
 * Extract the storage key from the upper 8 bits of the page frame number
 * and store it in the page_key_data list of arrays.
 */
void page_key_memorize(unsigned long *pfn)
{
        page_key_wp->data[page_key_wx] = *(unsigned char *) pfn;
        *(unsigned char *) pfn = 0;
        if (++page_key_wx < PAGE_KEY_DATA_SIZE)
                return;
        page_key_wp = page_key_wp->next;
        page_key_wx = 0;
}

/*
 * Get the next key from the page_key_data list of arrays and set the
 * storage key of the page referred by @address. If @address refers to
 * a "safe" page the swsusp_arch_resume code will transfer the storage
 * key from the buffer page to the original page.
 */
void page_key_write(void *address)
{
        page_set_storage_key((unsigned long) address,
                             page_key_rp->data[page_key_rx], 0);
        if (++page_key_rx >= PAGE_KEY_DATA_SIZE)
                return;
        page_key_rp = page_key_rp->next;
        page_key_rx = 0;
}

int pfn_is_nosave(unsigned long pfn)
{
        unsigned long nosave_begin_pfn = PFN_DOWN(__pa(&__nosave_begin));
        unsigned long nosave_end_pfn = PFN_DOWN(__pa(&__nosave_end));

        /* Always save lowcore pages (LC protection might be enabled). */
        if (pfn <= LC_PAGES)
                return 0;
        if (pfn >= nosave_begin_pfn && pfn < nosave_end_pfn)
                return 1;
        /* Skip memory holes and read-only pages (NSS, DCSS, ...). */
        if (tprot(PFN_PHYS(pfn)))
                return 1;
        return 0;
}

void save_processor_state(void)
{
        /* swsusp_arch_suspend() actually saves all cpu register contents.
         * Machine checks must be disabled since swsusp_arch_suspend() stores
         * register contents to their lowcore save areas. That's the same
         * place where register contents on machine checks would be saved.
         * To avoid register corruption disable machine checks.
         * We must also disable machine checks in the new psw mask for
         * program checks, since swsusp_arch_suspend() may generate program
         * checks. Disabling machine checks for all other new psw masks is
         * just paranoia.
         */
        local_mcck_disable();
        /* Disable lowcore protection */
        __ctl_clear_bit(0,28);
        S390_lowcore.external_new_psw.mask &= ~PSW_MASK_MCHECK;
        S390_lowcore.svc_new_psw.mask &= ~PSW_MASK_MCHECK;
        S390_lowcore.io_new_psw.mask &= ~PSW_MASK_MCHECK;
        S390_lowcore.program_new_psw.mask &= ~PSW_MASK_MCHECK;
}

void restore_processor_state(void)
{
        S390_lowcore.external_new_psw.mask |= PSW_MASK_MCHECK;
        S390_lowcore.svc_new_psw.mask |= PSW_MASK_MCHECK;
        S390_lowcore.io_new_psw.mask |= PSW_MASK_MCHECK;
        S390_lowcore.program_new_psw.mask |= PSW_MASK_MCHECK;
        /* Enable lowcore protection */
        __ctl_set_bit(0,28);
        local_mcck_enable();
}