arch/tile/include/asm/cache.h

/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   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, version 2.
 *
 *   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, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#ifndef _ASM_TILE_CACHE_H
#define _ASM_TILE_CACHE_H

#include <arch/chip.h>

/* bytes per L1 data cache line */
#define L1_CACHE_SHIFT		CHIP_L1D_LOG_LINE_SIZE()
#define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)

/* bytes per L2 cache line */
#define L2_CACHE_SHIFT		CHIP_L2_LOG_LINE_SIZE()
#define L2_CACHE_BYTES		(1 << L2_CACHE_SHIFT)
#define L2_CACHE_ALIGN(x)	(((x)+(L2_CACHE_BYTES-1)) & -L2_CACHE_BYTES)

/*
 * TILEPro I/O is not always coherent (networking typically uses coherent
 * I/O, but PCI traffic does not) and setting ARCH_DMA_MINALIGN to the
 * L2 cacheline size helps ensure that kernel heap allocations are aligned.
 * TILE-Gx I/O is always coherent when used on hash-for-home pages.
 *
 * However, it's possible at runtime to request not to use hash-for-home
 * for the kernel heap, in which case the kernel will use flush-and-inval
 * to manage coherence.  As a result, we use L2_CACHE_BYTES for the
 * DMA minimum alignment to avoid false sharing in the kernel heap.
 */
#define ARCH_DMA_MINALIGN	L2_CACHE_BYTES

/* use the cache line size for the L2, which is where it counts */
#define SMP_CACHE_BYTES_SHIFT	L2_CACHE_SHIFT
#define SMP_CACHE_BYTES		L2_CACHE_BYTES
#define INTERNODE_CACHE_SHIFT   L2_CACHE_SHIFT
#define INTERNODE_CACHE_BYTES   L2_CACHE_BYTES

/* Group together read-mostly things to avoid cache false sharing */
#define __read_mostly __attribute__((__section__(".data..read_mostly")))

/*
 * Originally we used small TLB pages for kernel data and grouped some
 * things together as "write once", enforcing the property at the end
 * of initialization by making those pages read-only and non-coherent.
 * This allowed better cache utilization since cache inclusion did not
 * need to be maintained.  However, to do this requires an extra TLB
 * entry, which on balance is more of a performance hit than the
 * non-coherence is a performance gain, so we now just make "read
 * mostly" and "write once" be synonyms.  We keep the attribute
 * separate in case we change our minds at a future date.
 */
#define __write_once __read_mostly

/* __ro_after_init is the generic name for the tile arch __write_once. */
#define __ro_after_init __read_mostly

#endif /* _ASM_TILE_CACHE_H */