/*
 * Copyright IBM Corporation, 2015
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

#include <linux/mm.h>
#include <asm/machdep.h>
#include <asm/mmu.h>

int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
		   pte_t *ptep, unsigned long trap, unsigned long flags,
		   int ssize, int subpg_prot)
{
	real_pte_t rpte;
	unsigned long hpte_group;
	unsigned long rflags, pa;
	unsigned long old_pte, new_pte;
	unsigned long vpn, hash, slot;
	unsigned long shift = mmu_psize_defs[MMU_PAGE_4K].shift;

	/*
	 * atomically mark the linux large page PTE busy and dirty
	 */
	do {
		pte_t pte = READ_ONCE(*ptep);

		old_pte = pte_val(pte);
		/* If PTE busy, retry the access */
		if (unlikely(old_pte & H_PAGE_BUSY))
			return 0;
		/* If PTE permissions don't match, take page fault */
		if (unlikely(!check_pte_access(access, old_pte)))
			return 1;
		/*
		 * Try to lock the PTE, add ACCESSED and DIRTY if it was
		 * a write access. Since this is 4K insert of 64K page size
		 * also add H_PAGE_COMBO
		 */
		new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED;
		if (access & _PAGE_WRITE)
			new_pte |= _PAGE_DIRTY;
	} while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));

	/*
	 * PP bits. _PAGE_USER is already PP bit 0x2, so we only
	 * need to add in 0x1 if it's a read-only user page
	 */
	rflags = htab_convert_pte_flags(new_pte);
	rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);

	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);

	vpn  = hpt_vpn(ea, vsid, ssize);
	if (unlikely(old_pte & H_PAGE_HASHPTE)) {
		/*
		 * There MIGHT be an HPTE for this pte
		 */
		unsigned long gslot = pte_get_hash_gslot(vpn, shift, ssize,
							 rpte, 0);

		if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_4K,
					       MMU_PAGE_4K, ssize, flags) == -1)
			old_pte &= ~_PAGE_HPTEFLAGS;
	}

	if (likely(!(old_pte & H_PAGE_HASHPTE))) {

		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
		hash = hpt_hash(vpn, shift, ssize);

repeat:
		hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;

		/* Insert into the hash table, primary slot */
		slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
						MMU_PAGE_4K, MMU_PAGE_4K, ssize);
		/*
		 * Primary is full, try the secondary
		 */
		if (unlikely(slot == -1)) {
			hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
			slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
							rflags,
							HPTE_V_SECONDARY,
							MMU_PAGE_4K,
							MMU_PAGE_4K, ssize);
			if (slot == -1) {
				if (mftb() & 0x1)
					hpte_group = (hash & htab_hash_mask) *
							HPTES_PER_GROUP;
				mmu_hash_ops.hpte_remove(hpte_group);
				/*
				 * FIXME!! Should be try the group from which we removed ?
				 */
				goto repeat;
			}
		}
		/*
		 * Hypervisor failure. Restore old pte and return -1
		 * similar to __hash_page_*
		 */
		if (unlikely(slot == -2)) {
			*ptep = __pte(old_pte);
			hash_failure_debug(ea, access, vsid, trap, ssize,
					   MMU_PAGE_4K, MMU_PAGE_4K, old_pte);
			return -1;
		}
		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
		new_pte |= pte_set_hidx(ptep, rpte, 0, slot, PTRS_PER_PTE);
	}
	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
	return 0;
}