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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/tile/include/asm/cache.h
Initial import
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+/*
+ * 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
+
+#endif /* _ASM_TILE_CACHE_H */