summaryrefslogtreecommitdiffstats
path: root/arch/tile/lib/cacheflush.c
blob: 9c0ec22009a5ed833fab76a6e8ee94a9c1a1685f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
/*
 * 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.
 */

#include <linux/export.h>
#include <asm/page.h>
#include <asm/cacheflush.h>
#include <arch/icache.h>
#include <arch/spr_def.h>


void __flush_icache_range(unsigned long start, unsigned long end)
{
	invalidate_icache((const void *)start, end - start, PAGE_SIZE);
}


/* Force a load instruction to issue. */
static inline void force_load(char *p)
{
	*(volatile char *)p;
}

/*
 * Flush and invalidate a VA range that is homed remotely on a single
 * core (if "!hfh") or homed via hash-for-home (if "hfh"), waiting
 * until the memory controller holds the flushed values.
 */
void __attribute__((optimize("omit-frame-pointer")))
finv_buffer_remote(void *buffer, size_t size, int hfh)
{
	char *p, *base;
	size_t step_size, load_count;

	/*
	 * On TILEPro the striping granularity is a fixed 8KB; on
	 * TILE-Gx it is configurable, and we rely on the fact that
	 * the hypervisor always configures maximum striping, so that
	 * bits 9 and 10 of the PA are part of the stripe function, so
	 * every 512 bytes we hit a striping boundary.
	 *
	 */
#ifdef __tilegx__
	const unsigned long STRIPE_WIDTH = 512;
#else
	const unsigned long STRIPE_WIDTH = 8192;
#endif

#ifdef __tilegx__
	/*
	 * On TILE-Gx, we must disable the dstream prefetcher before doing
	 * a cache flush; otherwise, we could end up with data in the cache
	 * that we don't want there.  Note that normally we'd do an mf
	 * after the SPR write to disabling the prefetcher, but we do one
	 * below, before any further loads, so there's no need to do it
	 * here.
	 */
	uint_reg_t old_dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
	__insn_mtspr(SPR_DSTREAM_PF, 0);
#endif

	/*
	 * Flush and invalidate the buffer out of the local L1/L2
	 * and request the home cache to flush and invalidate as well.
	 */
	__finv_buffer(buffer, size);

	/*
	 * Wait for the home cache to acknowledge that it has processed
	 * all the flush-and-invalidate requests.  This does not mean
	 * that the flushed data has reached the memory controller yet,
	 * but it does mean the home cache is processing the flushes.
	 */
	__insn_mf();

	/*
	 * Issue a load to the last cache line, which can't complete
	 * until all the previously-issued flushes to the same memory
	 * controller have also completed.  If we weren't striping
	 * memory, that one load would be sufficient, but since we may
	 * be, we also need to back up to the last load issued to
	 * another memory controller, which would be the point where
	 * we crossed a "striping" boundary (the granularity of striping
	 * across memory controllers).  Keep backing up and doing this
	 * until we are before the beginning of the buffer, or have
	 * hit all the controllers.
	 *
	 * If we are flushing a hash-for-home buffer, it's even worse.
	 * Each line may be homed on a different tile, and each tile
	 * may have up to four lines that are on different
	 * controllers.  So as we walk backwards, we have to touch
	 * enough cache lines to satisfy these constraints.  In
	 * practice this ends up being close enough to "load from
	 * every cache line on a full memory stripe on each
	 * controller" that we simply do that, to simplify the logic.
	 *
	 * On TILE-Gx the hash-for-home function is much more complex,
	 * with the upshot being we can't readily guarantee we have
	 * hit both entries in the 128-entry AMT that were hit by any
	 * load in the entire range, so we just re-load them all.
	 * With larger buffers, we may want to consider using a hypervisor
	 * trap to issue loads directly to each hash-for-home tile for
	 * each controller (doing it from Linux would trash the TLB).
	 */
	if (hfh) {
		step_size = L2_CACHE_BYTES;
#ifdef __tilegx__
		load_count = (size + L2_CACHE_BYTES - 1) / L2_CACHE_BYTES;
#else
		load_count = (STRIPE_WIDTH / L2_CACHE_BYTES) *
			      (1 << CHIP_LOG_NUM_MSHIMS());
#endif
	} else {
		step_size = STRIPE_WIDTH;
		load_count = (1 << CHIP_LOG_NUM_MSHIMS());
	}

	/* Load the last byte of the buffer. */
	p = (char *)buffer + size - 1;
	force_load(p);

	/* Bump down to the end of the previous stripe or cache line. */
	p -= step_size;
	p = (char *)((unsigned long)p | (step_size - 1));

	/* Figure out how far back we need to go. */
	base = p - (step_size * (load_count - 2));
	if ((unsigned long)base < (unsigned long)buffer)
		base = buffer;

	/*
	 * Fire all the loads we need.  The MAF only has eight entries
	 * so we can have at most eight outstanding loads, so we
	 * unroll by that amount.
	 */
#pragma unroll 8
	for (; p >= base; p -= step_size)
		force_load(p);

	/*
	 * Repeat, but with finv's instead of loads, to get rid of the
	 * data we just loaded into our own cache and the old home L3.
	 * No need to unroll since finv's don't target a register.
	 * The finv's are guaranteed not to actually flush the data in
	 * the buffer back to their home, since we just read it, so the
	 * lines are clean in cache; we will only invalidate those lines.
	 */
	p = (char *)buffer + size - 1;
	__insn_finv(p);
	p -= step_size;
	p = (char *)((unsigned long)p | (step_size - 1));
	for (; p >= base; p -= step_size)
		__insn_finv(p);

	/* Wait for these finv's (and thus the first finvs) to be done. */
	__insn_mf();

#ifdef __tilegx__
	/* Reenable the prefetcher. */
	__insn_mtspr(SPR_DSTREAM_PF, old_dstream_pf);
#endif
}
EXPORT_SYMBOL_GPL(finv_buffer_remote);