1/*
2 * Copyright (C) 2001-2006 Silicon Graphics, Inc.  All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of version 2 of the GNU General Public License
6 * as published by the Free Software Foundation.
7 *
8 * A simple uncached page allocator using the generic allocator. This
9 * allocator first utilizes the spare (spill) pages found in the EFI
10 * memmap and will then start converting cached pages to uncached ones
11 * at a granule at a time. Node awareness is implemented by having a
12 * pool of pages per node.
13 */
14
15#include <linux/types.h>
16#include <linux/kernel.h>
17#include <linux/module.h>
18#include <linux/init.h>
19#include <linux/errno.h>
20#include <linux/string.h>
21#include <linux/slab.h>
22#include <linux/efi.h>
23#include <linux/genalloc.h>
24#include <asm/page.h>
25#include <asm/pal.h>
26#include <asm/system.h>
27#include <asm/pgtable.h>
28#include <asm/atomic.h>
29#include <asm/tlbflush.h>
30#include <asm/sn/arch.h>
31
32
33extern void __init efi_memmap_walk_uc(efi_freemem_callback_t, void *);
34
35struct uncached_pool {
36	struct gen_pool *pool;
37	struct mutex add_chunk_mutex;	/* serialize adding a converted chunk */
38	int nchunks_added;		/* #of converted chunks added to pool */
39	atomic_t status;		/* smp called function's return status*/
40};
41
42#define MAX_CONVERTED_CHUNKS_PER_NODE	2
43
44struct uncached_pool uncached_pools[MAX_NUMNODES];
45
46
47static void uncached_ipi_visibility(void *data)
48{
49	int status;
50	struct uncached_pool *uc_pool = (struct uncached_pool *)data;
51
52	status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
53	if ((status != PAL_VISIBILITY_OK) &&
54	    (status != PAL_VISIBILITY_OK_REMOTE_NEEDED))
55		atomic_inc(&uc_pool->status);
56}
57
58
59static void uncached_ipi_mc_drain(void *data)
60{
61	int status;
62	struct uncached_pool *uc_pool = (struct uncached_pool *)data;
63
64	status = ia64_pal_mc_drain();
65	if (status != PAL_STATUS_SUCCESS)
66		atomic_inc(&uc_pool->status);
67}
68
69
70/*
71 * Add a new chunk of uncached memory pages to the specified pool.
72 *
73 * @pool: pool to add new chunk of uncached memory to
74 * @nid: node id of node to allocate memory from, or -1
75 *
76 * This is accomplished by first allocating a granule of cached memory pages
77 * and then converting them to uncached memory pages.
78 */
79static int uncached_add_chunk(struct uncached_pool *uc_pool, int nid)
80{
81	struct page *page;
82	int status, i, nchunks_added = uc_pool->nchunks_added;
83	unsigned long c_addr, uc_addr;
84
85	if (mutex_lock_interruptible(&uc_pool->add_chunk_mutex) != 0)
86		return -1;	/* interrupted by a signal */
87
88	if (uc_pool->nchunks_added > nchunks_added) {
89		/* someone added a new chunk while we were waiting */
90		mutex_unlock(&uc_pool->add_chunk_mutex);
91		return 0;
92	}
93
94	if (uc_pool->nchunks_added >= MAX_CONVERTED_CHUNKS_PER_NODE) {
95		mutex_unlock(&uc_pool->add_chunk_mutex);
96		return -1;
97	}
98
99	/* attempt to allocate a granule's worth of cached memory pages */
100
101	page = alloc_pages_node(nid, GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
102				IA64_GRANULE_SHIFT-PAGE_SHIFT);
103	if (!page) {
104		mutex_unlock(&uc_pool->add_chunk_mutex);
105		return -1;
106	}
107
108	/* convert the memory pages from cached to uncached */
109
110	c_addr = (unsigned long)page_address(page);
111	uc_addr = c_addr - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;
112
113	/*
114	 * There's a small race here where it's possible for someone to
115	 * access the page through /dev/mem halfway through the conversion
116	 * to uncached - not sure it's really worth bothering about
117	 */
118	for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
119		SetPageUncached(&page[i]);
120
121	flush_tlb_kernel_range(uc_addr, uc_adddr + IA64_GRANULE_SIZE);
122
123	status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
124	if (status == PAL_VISIBILITY_OK_REMOTE_NEEDED) {
125		atomic_set(&uc_pool->status, 0);
126		status = smp_call_function(uncached_ipi_visibility, uc_pool,
127					   0, 1);
128		if (status || atomic_read(&uc_pool->status))
129			goto failed;
130	} else if (status != PAL_VISIBILITY_OK)
131		goto failed;
132
133	preempt_disable();
134
135	if (ia64_platform_is("sn2"))
136		sn_flush_all_caches(uc_addr, IA64_GRANULE_SIZE);
137	else
138		flush_icache_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);
139
140	/* flush the just introduced uncached translation from the TLB */
141	local_flush_tlb_all();
142
143	preempt_enable();
144
145	status = ia64_pal_mc_drain();
146	if (status != PAL_STATUS_SUCCESS)
147		goto failed;
148	atomic_set(&uc_pool->status, 0);
149	status = smp_call_function(uncached_ipi_mc_drain, uc_pool, 0, 1);
150	if (status || atomic_read(&uc_pool->status))
151		goto failed;
152
153	/*
154	 * The chunk of memory pages has been converted to uncached so now we
155	 * can add it to the pool.
156	 */
157	status = gen_pool_add(uc_pool->pool, uc_addr, IA64_GRANULE_SIZE, nid);
158	if (status)
159		goto failed;
160
161	uc_pool->nchunks_added++;
162	mutex_unlock(&uc_pool->add_chunk_mutex);
163	return 0;
164
165	/* failed to convert or add the chunk so give it back to the kernel */
166failed:
167	for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
168		ClearPageUncached(&page[i]);
169
170	free_pages(c_addr, IA64_GRANULE_SHIFT-PAGE_SHIFT);
171	mutex_unlock(&uc_pool->add_chunk_mutex);
172	return -1;
173}
174
175
176/*
177 * uncached_alloc_page
178 *
179 * @starting_nid: node id of node to start with, or -1
180 *
181 * Allocate 1 uncached page. Allocates on the requested node. If no
182 * uncached pages are available on the requested node, roundrobin starting
183 * with the next higher node.
184 */
185unsigned long uncached_alloc_page(int starting_nid)
186{
187	unsigned long uc_addr;
188	struct uncached_pool *uc_pool;
189	int nid;
190
191	if (unlikely(starting_nid >= MAX_NUMNODES))
192		return 0;
193
194	if (starting_nid < 0)
195		starting_nid = numa_node_id();
196	nid = starting_nid;
197
198	do {
199		if (!node_online(nid))
200			continue;
201		uc_pool = &uncached_pools[nid];
202		if (uc_pool->pool == NULL)
203			continue;
204		do {
205			uc_addr = gen_pool_alloc(uc_pool->pool, PAGE_SIZE);
206			if (uc_addr != 0)
207				return uc_addr;
208		} while (uncached_add_chunk(uc_pool, nid) == 0);
209
210	} while ((nid = (nid + 1) % MAX_NUMNODES) != starting_nid);
211
212	return 0;
213}
214EXPORT_SYMBOL(uncached_alloc_page);
215
216
217/*
218 * uncached_free_page
219 *
220 * @uc_addr: uncached address of page to free
221 *
222 * Free a single uncached page.
223 */
224void uncached_free_page(unsigned long uc_addr)
225{
226	int nid = paddr_to_nid(uc_addr - __IA64_UNCACHED_OFFSET);
227	struct gen_pool *pool = uncached_pools[nid].pool;
228
229	if (unlikely(pool == NULL))
230		return;
231
232	if ((uc_addr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
233		panic("uncached_free_page invalid address %lx\n", uc_addr);
234
235	gen_pool_free(pool, uc_addr, PAGE_SIZE);
236}
237EXPORT_SYMBOL(uncached_free_page);
238
239
240/*
241 * uncached_build_memmap,
242 *
243 * @uc_start: uncached starting address of a chunk of uncached memory
244 * @uc_end: uncached ending address of a chunk of uncached memory
245 * @arg: ignored, (NULL argument passed in on call to efi_memmap_walk_uc())
246 *
247 * Called at boot time to build a map of pages that can be used for
248 * memory special operations.
249 */
250static int __init uncached_build_memmap(unsigned long uc_start,
251					unsigned long uc_end, void *arg)
252{
253	int nid = paddr_to_nid(uc_start - __IA64_UNCACHED_OFFSET);
254	struct gen_pool *pool = uncached_pools[nid].pool;
255	size_t size = uc_end - uc_start;
256
257	touch_softlockup_watchdog();
258
259	if (pool != NULL) {
260		memset((char *)uc_start, 0, size);
261		(void) gen_pool_add(pool, uc_start, size, nid);
262	}
263	return 0;
264}
265
266
267static int __init uncached_init(void)
268{
269	int nid;
270
271	for_each_online_node(nid) {
272		uncached_pools[nid].pool = gen_pool_create(PAGE_SHIFT, nid);
273		mutex_init(&uncached_pools[nid].add_chunk_mutex);
274	}
275
276	efi_memmap_walk_uc(uncached_build_memmap, NULL);
277	return 0;
278}
279
280__initcall(uncached_init);
281