1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Broadcom Brahma-B15 CPU read-ahead cache management functions
4 *
5 * Copyright (C) 2015-2016 Broadcom
6 */
7
8 #include <linux/err.h>
9 #include <linux/spinlock.h>
10 #include <linux/io.h>
11 #include <linux/bitops.h>
12 #include <linux/of_address.h>
13 #include <linux/notifier.h>
14 #include <linux/cpu.h>
15 #include <linux/syscore_ops.h>
16 #include <linux/reboot.h>
17
18 #include <asm/cacheflush.h>
19 #include <asm/hardware/cache-b15-rac.h>
20
21 extern void v7_flush_kern_cache_all(void);
22
23 /* RAC register offsets, relative to the HIF_CPU_BIUCTRL register base */
24 #define RAC_CONFIG0_REG (0x78)
25 #define RACENPREF_MASK (0x3)
26 #define RACPREFINST_SHIFT (0)
27 #define RACENINST_SHIFT (2)
28 #define RACPREFDATA_SHIFT (4)
29 #define RACENDATA_SHIFT (6)
30 #define RAC_CPU_SHIFT (8)
31 #define RACCFG_MASK (0xff)
32 #define RAC_CONFIG1_REG (0x7c)
33 /* Brahma-B15 is a quad-core only design */
34 #define B15_RAC_FLUSH_REG (0x80)
35 /* Brahma-B53 is an octo-core design */
36 #define B53_RAC_FLUSH_REG (0x84)
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
51 static void __iomem *b15_rac_base;
52 static DEFINE_SPINLOCK(rac_lock);
53
54 static u32 rac_config0_reg;
55 static u32 rac_flush_offset;
56
57 /* Initialization flag to avoid checking for b15_rac_base, and to prevent
58 * multi-platform kernels from crashing here as well.
59 */
60 static unsigned long b15_rac_flags;
61
__b15_rac_disable(void)62 static inline u32 __b15_rac_disable(void)
63 {
64 u32 val = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
65 __raw_writel(0, b15_rac_base + RAC_CONFIG0_REG);
66 dmb();
67 return val;
68 }
69
__b15_rac_flush(void)70 static inline void __b15_rac_flush(void)
71 {
72 u32 reg;
73
74 __raw_writel(FLUSH_RAC, b15_rac_base + rac_flush_offset);
75 do {
76 /* This dmb() is required to force the Bus Interface Unit
77 * to clean outstanding writes, and forces an idle cycle
78 * to be inserted.
79 */
80 dmb();
81 reg = __raw_readl(b15_rac_base + rac_flush_offset);
82 } while (reg & FLUSH_RAC);
83 }
84
b15_rac_disable_and_flush(void)85 static inline u32 b15_rac_disable_and_flush(void)
86 {
87 u32 reg;
88
89 reg = __b15_rac_disable();
90 __b15_rac_flush();
91 return reg;
92 }
93
__b15_rac_enable(u32 val)94 static inline void __b15_rac_enable(u32 val)
95 {
96 __raw_writel(val, b15_rac_base + RAC_CONFIG0_REG);
97 /* dsb() is required here to be consistent with __flush_icache_all() */
98 dsb();
99 }
100
101 #define BUILD_RAC_CACHE_OP(name, bar) \
102 void b15_flush_##name(void) \
103 { \
104 unsigned int do_flush; \
105 u32 val = 0; \
106 \
107 if (test_bit(RAC_SUSPENDED, &b15_rac_flags)) { \
108 v7_flush_##name(); \
109 bar; \
110 return; \
111 } \
112 \
113 spin_lock(&rac_lock); \
114 do_flush = test_bit(RAC_ENABLED, &b15_rac_flags); \
115 if (do_flush) \
116 val = b15_rac_disable_and_flush(); \
117 v7_flush_##name(); \
118 if (!do_flush) \
119 bar; \
120 else \
121 __b15_rac_enable(val); \
122 spin_unlock(&rac_lock); \
123 }
124
125 #define nobarrier
126
127 /* The readahead cache present in the Brahma-B15 CPU is a special piece of
128 * hardware after the integrated L2 cache of the B15 CPU complex whose purpose
129 * is to prefetch instruction and/or data with a line size of either 64 bytes
130 * or 256 bytes. The rationale is that the data-bus of the CPU interface is
131 * optimized for 256-bytes transactions, and enabling the readahead cache
132 * provides a significant performance boost we want it enabled (typically
133 * twice the performance for a memcpy benchmark application).
134 *
135 * The readahead cache is transparent for Modified Virtual Addresses
136 * cache maintenance operations: ICIMVAU, DCIMVAC, DCCMVAC, DCCMVAU and
137 * DCCIMVAC.
138 *
139 * It is however not transparent for the following cache maintenance
140 * operations: DCISW, DCCSW, DCCISW, ICIALLUIS and ICIALLU which is precisely
141 * what we are patching here with our BUILD_RAC_CACHE_OP here.
142 */
143 BUILD_RAC_CACHE_OP(kern_cache_all, nobarrier);
144
b15_rac_enable(void)145 static void b15_rac_enable(void)
146 {
147 unsigned int cpu;
148 u32 enable = 0;
149
150 for_each_possible_cpu(cpu)
151 enable |= (RAC_DATA_INST_EN_MASK << (cpu * RAC_CPU_SHIFT));
152
153 b15_rac_disable_and_flush();
154 __b15_rac_enable(enable);
155 }
156
b15_rac_reboot_notifier(struct notifier_block * nb,unsigned long action,void * data)157 static int b15_rac_reboot_notifier(struct notifier_block *nb,
158 unsigned long action,
159 void *data)
160 {
161 /* During kexec, we are not yet migrated on the boot CPU, so we need to
162 * make sure we are SMP safe here. Once the RAC is disabled, flag it as
163 * suspended such that the hotplug notifier returns early.
164 */
165 if (action == SYS_RESTART) {
166 spin_lock(&rac_lock);
167 b15_rac_disable_and_flush();
168 clear_bit(RAC_ENABLED, &b15_rac_flags);
169 set_bit(RAC_SUSPENDED, &b15_rac_flags);
170 spin_unlock(&rac_lock);
171 }
172
173 return NOTIFY_DONE;
174 }
175
176 static struct notifier_block b15_rac_reboot_nb = {
177 .notifier_call = b15_rac_reboot_notifier,
178 };
179
180 /* The CPU hotplug case is the most interesting one, we basically need to make
181 * sure that the RAC is disabled for the entire system prior to having a CPU
182 * die, in particular prior to this dying CPU having exited the coherency
183 * domain.
184 *
185 * Once this CPU is marked dead, we can safely re-enable the RAC for the
186 * remaining CPUs in the system which are still online.
187 *
188 * Offlining a CPU is the problematic case, onlining a CPU is not much of an
189 * issue since the CPU and its cache-level hierarchy will start filling with
190 * the RAC disabled, so L1 and L2 only.
191 *
192 * In this function, we should NOT have to verify any unsafe setting/condition
193 * b15_rac_base:
194 *
195 * It is protected by the RAC_ENABLED flag which is cleared by default, and
196 * being cleared when initial procedure is done. b15_rac_base had been set at
197 * that time.
198 *
199 * RAC_ENABLED:
200 * There is a small timing windows, in b15_rac_init(), between
201 * cpuhp_setup_state_*()
202 * ...
203 * set RAC_ENABLED
204 * However, there is no hotplug activity based on the Linux booting procedure.
205 *
206 * Since we have to disable RAC for all cores, we keep RAC on as long as as
207 * possible (disable it as late as possible) to gain the cache benefit.
208 *
209 * Thus, dying/dead states are chosen here
210 *
211 * We are choosing not do disable the RAC on a per-CPU basis, here, if we did
212 * we would want to consider disabling it as early as possible to benefit the
213 * other active CPUs.
214 */
215
216 /* Running on the dying CPU */
b15_rac_dying_cpu(unsigned int cpu)217 static int b15_rac_dying_cpu(unsigned int cpu)
218 {
219 /* During kexec/reboot, the RAC is disabled via the reboot notifier
220 * return early here.
221 */
222 if (test_bit(RAC_SUSPENDED, &b15_rac_flags))
223 return 0;
224
225 spin_lock(&rac_lock);
226
227 /* Indicate that we are starting a hotplug procedure */
228 __clear_bit(RAC_ENABLED, &b15_rac_flags);
229
230 /* Disable the readahead cache and save its value to a global */
231 rac_config0_reg = b15_rac_disable_and_flush();
232
233 spin_unlock(&rac_lock);
234
235 return 0;
236 }
237
238 /* Running on a non-dying CPU */
b15_rac_dead_cpu(unsigned int cpu)239 static int b15_rac_dead_cpu(unsigned int cpu)
240 {
241 /* During kexec/reboot, the RAC is disabled via the reboot notifier
242 * return early here.
243 */
244 if (test_bit(RAC_SUSPENDED, &b15_rac_flags))
245 return 0;
246
247 spin_lock(&rac_lock);
248
249 /* And enable it */
250 __b15_rac_enable(rac_config0_reg);
251 __set_bit(RAC_ENABLED, &b15_rac_flags);
252
253 spin_unlock(&rac_lock);
254
255 return 0;
256 }
257
b15_rac_suspend(void)258 static int b15_rac_suspend(void)
259 {
260 /* Suspend the read-ahead cache oeprations, forcing our cache
261 * implementation to fallback to the regular ARMv7 calls.
262 *
263 * We are guaranteed to be running on the boot CPU at this point and
264 * with every other CPU quiesced, so setting RAC_SUSPENDED is not racy
265 * here.
266 */
267 rac_config0_reg = b15_rac_disable_and_flush();
268 set_bit(RAC_SUSPENDED, &b15_rac_flags);
269
270 return 0;
271 }
272
b15_rac_resume(void)273 static void b15_rac_resume(void)
274 {
275 /* Coming out of a S3 suspend/resume cycle, the read-ahead cache
276 * register RAC_CONFIG0_REG will be restored to its default value, make
277 * sure we re-enable it and set the enable flag, we are also guaranteed
278 * to run on the boot CPU, so not racy again.
279 */
280 __b15_rac_enable(rac_config0_reg);
281 clear_bit(RAC_SUSPENDED, &b15_rac_flags);
282 }
283
284 static struct syscore_ops b15_rac_syscore_ops = {
285 .suspend = b15_rac_suspend,
286 .resume = b15_rac_resume,
287 };
288
b15_rac_init(void)289 static int __init b15_rac_init(void)
290 {
291 struct device_node *dn, *cpu_dn;
292 int ret = 0, cpu;
293 u32 reg, en_mask = 0;
294
295 dn = of_find_compatible_node(NULL, NULL, "brcm,brcmstb-cpu-biu-ctrl");
296 if (!dn)
297 return -ENODEV;
298
299 if (WARN(num_possible_cpus() > 4, "RAC only supports 4 CPUs\n"))
300 goto out;
301
302 b15_rac_base = of_iomap(dn, 0);
303 if (!b15_rac_base) {
304 pr_err("failed to remap BIU control base\n");
305 ret = -ENOMEM;
306 goto out;
307 }
308
309 cpu_dn = of_get_cpu_node(0, NULL);
310 if (!cpu_dn) {
311 ret = -ENODEV;
312 goto out;
313 }
314
315 if (of_device_is_compatible(cpu_dn, "brcm,brahma-b15"))
316 rac_flush_offset = B15_RAC_FLUSH_REG;
317 else if (of_device_is_compatible(cpu_dn, "brcm,brahma-b53"))
318 rac_flush_offset = B53_RAC_FLUSH_REG;
319 else {
320 pr_err("Unsupported CPU\n");
321 of_node_put(cpu_dn);
322 ret = -EINVAL;
323 goto out;
324 }
325 of_node_put(cpu_dn);
326
327 ret = register_reboot_notifier(&b15_rac_reboot_nb);
328 if (ret) {
329 pr_err("failed to register reboot notifier\n");
330 iounmap(b15_rac_base);
331 goto out;
332 }
333
334 if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
335 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DEAD,
336 "arm/cache-b15-rac:dead",
337 NULL, b15_rac_dead_cpu);
338 if (ret)
339 goto out_unmap;
340
341 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING,
342 "arm/cache-b15-rac:dying",
343 NULL, b15_rac_dying_cpu);
344 if (ret)
345 goto out_cpu_dead;
346 }
347
348 if (IS_ENABLED(CONFIG_PM_SLEEP))
349 register_syscore_ops(&b15_rac_syscore_ops);
350
351 spin_lock(&rac_lock);
352 reg = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
353 for_each_possible_cpu(cpu)
354 en_mask |= ((1 << RACPREFDATA_SHIFT) << (cpu * RAC_CPU_SHIFT));
355 WARN(reg & en_mask, "Read-ahead cache not previously disabled\n");
356
357 b15_rac_enable();
358 set_bit(RAC_ENABLED, &b15_rac_flags);
359 spin_unlock(&rac_lock);
360
361 pr_info("%pOF: Broadcom Brahma-B15 readahead cache\n", dn);
362
363 goto out;
364
365 out_cpu_dead:
366 cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING);
367 out_unmap:
368 unregister_reboot_notifier(&b15_rac_reboot_nb);
369 iounmap(b15_rac_base);
370 out:
371 of_node_put(dn);
372 return ret;
373 }
374 arch_initcall(b15_rac_init);
375
