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1/*
2 * Broadcom Brahma-B15 CPU read-ahead cache management functions
3 *
4 * Copyright (C) 2015-2016 Broadcom
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <linux/err.h>
12#include <linux/spinlock.h>
13#include <linux/io.h>
14#include <linux/bitops.h>
15#include <linux/of_address.h>
16#include <linux/notifier.h>
17#include <linux/cpu.h>
18#include <linux/syscore_ops.h>
19#include <linux/reboot.h>
20
21#include <asm/cacheflush.h>
22#include <asm/hardware/cache-b15-rac.h>
23
24extern void v7_flush_kern_cache_all(void);
25
26/* RAC register offsets, relative to the HIF_CPU_BIUCTRL register base */
27#define RAC_CONFIG0_REG (0x78)
28#define RACENPREF_MASK (0x3)
29#define RACPREFINST_SHIFT (0)
30#define RACENINST_SHIFT (2)
31#define RACPREFDATA_SHIFT (4)
32#define RACENDATA_SHIFT (6)
33#define RAC_CPU_SHIFT (8)
34#define RACCFG_MASK (0xff)
35#define RAC_CONFIG1_REG (0x7c)
36#define RAC_FLUSH_REG (0x80)
37#define FLUSH_RAC (1 << 0)
38
39/* Bitmask to enable instruction and data prefetching with a 256-bytes stride */
40#define RAC_DATA_INST_EN_MASK (1 << RACPREFINST_SHIFT | \
41 RACENPREF_MASK << RACENINST_SHIFT | \
42 1 << RACPREFDATA_SHIFT | \
43 RACENPREF_MASK << RACENDATA_SHIFT)
44
45#define RAC_ENABLED 0
46/* Special state where we want to bypass the spinlock and call directly
47 * into the v7 cache maintenance operations during suspend/resume
48 */
49#define RAC_SUSPENDED 1
50
51static void __iomem *b15_rac_base;
52static DEFINE_SPINLOCK(rac_lock);
53
54static u32 rac_config0_reg;
55
56/* Initialization flag to avoid checking for b15_rac_base, and to prevent
57 * multi-platform kernels from crashing here as well.
58 */
59static unsigned long b15_rac_flags;
60
61static inline u32 __b15_rac_disable(void)
62{
63 u32 val = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
64 __raw_writel(0, b15_rac_base + RAC_CONFIG0_REG);
65 dmb();
66 return val;
67}
68
69static inline void __b15_rac_flush(void)
70{
71 u32 reg;
72
73 __raw_writel(FLUSH_RAC, b15_rac_base + RAC_FLUSH_REG);
74 do {
75 /* This dmb() is required to force the Bus Interface Unit
76 * to clean oustanding writes, and forces an idle cycle
77 * to be inserted.
78 */
79 dmb();
80 reg = __raw_readl(b15_rac_base + RAC_FLUSH_REG);
81 } while (reg & FLUSH_RAC);
82}
83
84static inline u32 b15_rac_disable_and_flush(void)
85{
86 u32 reg;
87
88 reg = __b15_rac_disable();
89 __b15_rac_flush();
90 return reg;
91}
92
93static inline void __b15_rac_enable(u32 val)
94{
95 __raw_writel(val, b15_rac_base + RAC_CONFIG0_REG);
96 /* dsb() is required here to be consistent with __flush_icache_all() */
97 dsb();
98}
99
100#define BUILD_RAC_CACHE_OP(name, bar) \
101void b15_flush_##name(void) \
102{ \
103 unsigned int do_flush; \
104 u32 val = 0; \
105 \
106 if (test_bit(RAC_SUSPENDED, &b15_rac_flags)) { \
107 v7_flush_##name(); \
108 bar; \
109 return; \
110 } \
111 \
112 spin_lock(&rac_lock); \
113 do_flush = test_bit(RAC_ENABLED, &b15_rac_flags); \
114 if (do_flush) \
115 val = b15_rac_disable_and_flush(); \
116 v7_flush_##name(); \
117 if (!do_flush) \
118 bar; \
119 else \
120 __b15_rac_enable(val); \
121 spin_unlock(&rac_lock); \
122}
123
124#define nobarrier
125
126/* The readahead cache present in the Brahma-B15 CPU is a special piece of
127 * hardware after the integrated L2 cache of the B15 CPU complex whose purpose
128 * is to prefetch instruction and/or data with a line size of either 64 bytes
129 * or 256 bytes. The rationale is that the data-bus of the CPU interface is
130 * optimized for 256-bytes transactions, and enabling the readahead cache
131 * provides a significant performance boost we want it enabled (typically
132 * twice the performance for a memcpy benchmark application).
133 *
134 * The readahead cache is transparent for Modified Virtual Addresses
135 * cache maintenance operations: ICIMVAU, DCIMVAC, DCCMVAC, DCCMVAU and
136 * DCCIMVAC.
137 *
138 * It is however not transparent for the following cache maintenance
139 * operations: DCISW, DCCSW, DCCISW, ICIALLUIS and ICIALLU which is precisely
140 * what we are patching here with our BUILD_RAC_CACHE_OP here.
141 */
142BUILD_RAC_CACHE_OP(kern_cache_all, nobarrier);
143
144static void b15_rac_enable(void)
145{
146 unsigned int cpu;
147 u32 enable = 0;
148
149 for_each_possible_cpu(cpu)
150 enable |= (RAC_DATA_INST_EN_MASK << (cpu * RAC_CPU_SHIFT));
151
152 b15_rac_disable_and_flush();
153 __b15_rac_enable(enable);
154}
155
156static int b15_rac_reboot_notifier(struct notifier_block *nb,
157 unsigned long action,
158 void *data)
159{
160 /* During kexec, we are not yet migrated on the boot CPU, so we need to
161 * make sure we are SMP safe here. Once the RAC is disabled, flag it as
162 * suspended such that the hotplug notifier returns early.
163 */
164 if (action == SYS_RESTART) {
165 spin_lock(&rac_lock);
166 b15_rac_disable_and_flush();
167 clear_bit(RAC_ENABLED, &b15_rac_flags);
168 set_bit(RAC_SUSPENDED, &b15_rac_flags);
169 spin_unlock(&rac_lock);
170 }
171
172 return NOTIFY_DONE;
173}
174
175static struct notifier_block b15_rac_reboot_nb = {
176 .notifier_call = b15_rac_reboot_notifier,
177};
178
179/* The CPU hotplug case is the most interesting one, we basically need to make
180 * sure that the RAC is disabled for the entire system prior to having a CPU
181 * die, in particular prior to this dying CPU having exited the coherency
182 * domain.
183 *
184 * Once this CPU is marked dead, we can safely re-enable the RAC for the
185 * remaining CPUs in the system which are still online.
186 *
187 * Offlining a CPU is the problematic case, onlining a CPU is not much of an
188 * issue since the CPU and its cache-level hierarchy will start filling with
189 * the RAC disabled, so L1 and L2 only.
190 *
191 * In this function, we should NOT have to verify any unsafe setting/condition
192 * b15_rac_base:
193 *
194 * It is protected by the RAC_ENABLED flag which is cleared by default, and
195 * being cleared when initial procedure is done. b15_rac_base had been set at
196 * that time.
197 *
198 * RAC_ENABLED:
199 * There is a small timing windows, in b15_rac_init(), between
200 * cpuhp_setup_state_*()
201 * ...
202 * set RAC_ENABLED
203 * However, there is no hotplug activity based on the Linux booting procedure.
204 *
205 * Since we have to disable RAC for all cores, we keep RAC on as long as as
206 * possible (disable it as late as possible) to gain the cache benefit.
207 *
208 * Thus, dying/dead states are chosen here
209 *
210 * We are choosing not do disable the RAC on a per-CPU basis, here, if we did
211 * we would want to consider disabling it as early as possible to benefit the
212 * other active CPUs.
213 */
214
215/* Running on the dying CPU */
216static int b15_rac_dying_cpu(unsigned int cpu)
217{
218 /* During kexec/reboot, the RAC is disabled via the reboot notifier
219 * return early here.
220 */
221 if (test_bit(RAC_SUSPENDED, &b15_rac_flags))
222 return 0;
223
224 spin_lock(&rac_lock);
225
226 /* Indicate that we are starting a hotplug procedure */
227 __clear_bit(RAC_ENABLED, &b15_rac_flags);
228
229 /* Disable the readahead cache and save its value to a global */
230 rac_config0_reg = b15_rac_disable_and_flush();
231
232 spin_unlock(&rac_lock);
233
234 return 0;
235}
236
237/* Running on a non-dying CPU */
238static int b15_rac_dead_cpu(unsigned int cpu)
239{
240 /* During kexec/reboot, the RAC is disabled via the reboot notifier
241 * return early here.
242 */
243 if (test_bit(RAC_SUSPENDED, &b15_rac_flags))
244 return 0;
245
246 spin_lock(&rac_lock);
247
248 /* And enable it */
249 __b15_rac_enable(rac_config0_reg);
250 __set_bit(RAC_ENABLED, &b15_rac_flags);
251
252 spin_unlock(&rac_lock);
253
254 return 0;
255}
256
257static int b15_rac_suspend(void)
258{
259 /* Suspend the read-ahead cache oeprations, forcing our cache
260 * implementation to fallback to the regular ARMv7 calls.
261 *
262 * We are guaranteed to be running on the boot CPU at this point and
263 * with every other CPU quiesced, so setting RAC_SUSPENDED is not racy
264 * here.
265 */
266 rac_config0_reg = b15_rac_disable_and_flush();
267 set_bit(RAC_SUSPENDED, &b15_rac_flags);
268
269 return 0;
270}
271
272static void b15_rac_resume(void)
273{
274 /* Coming out of a S3 suspend/resume cycle, the read-ahead cache
275 * register RAC_CONFIG0_REG will be restored to its default value, make
276 * sure we re-enable it and set the enable flag, we are also guaranteed
277 * to run on the boot CPU, so not racy again.
278 */
279 __b15_rac_enable(rac_config0_reg);
280 clear_bit(RAC_SUSPENDED, &b15_rac_flags);
281}
282
283static struct syscore_ops b15_rac_syscore_ops = {
284 .suspend = b15_rac_suspend,
285 .resume = b15_rac_resume,
286};
287
288static int __init b15_rac_init(void)
289{
290 struct device_node *dn;
291 int ret = 0, cpu;
292 u32 reg, en_mask = 0;
293
294 dn = of_find_compatible_node(NULL, NULL, "brcm,brcmstb-cpu-biu-ctrl");
295 if (!dn)
296 return -ENODEV;
297
298 if (WARN(num_possible_cpus() > 4, "RAC only supports 4 CPUs\n"))
299 goto out;
300
301 b15_rac_base = of_iomap(dn, 0);
302 if (!b15_rac_base) {
303 pr_err("failed to remap BIU control base\n");
304 ret = -ENOMEM;
305 goto out;
306 }
307
308 ret = register_reboot_notifier(&b15_rac_reboot_nb);
309 if (ret) {
310 pr_err("failed to register reboot notifier\n");
311 iounmap(b15_rac_base);
312 goto out;
313 }
314
315 if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
316 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DEAD,
317 "arm/cache-b15-rac:dead",
318 NULL, b15_rac_dead_cpu);
319 if (ret)
320 goto out_unmap;
321
322 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING,
323 "arm/cache-b15-rac:dying",
324 NULL, b15_rac_dying_cpu);
325 if (ret)
326 goto out_cpu_dead;
327 }
328
329 if (IS_ENABLED(CONFIG_PM_SLEEP))
330 register_syscore_ops(&b15_rac_syscore_ops);
331
332 spin_lock(&rac_lock);
333 reg = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
334 for_each_possible_cpu(cpu)
335 en_mask |= ((1 << RACPREFDATA_SHIFT) << (cpu * RAC_CPU_SHIFT));
336 WARN(reg & en_mask, "Read-ahead cache not previously disabled\n");
337
338 b15_rac_enable();
339 set_bit(RAC_ENABLED, &b15_rac_flags);
340 spin_unlock(&rac_lock);
341
342 pr_info("Broadcom Brahma-B15 readahead cache at: 0x%p\n",
343 b15_rac_base + RAC_CONFIG0_REG);
344
345 goto out;
346
347out_cpu_dead:
348 cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING);
349out_unmap:
350 unregister_reboot_notifier(&b15_rac_reboot_nb);
351 iounmap(b15_rac_base);
352out:
353 of_node_put(dn);
354 return ret;
355}
356arch_initcall(b15_rac_init);