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/cfi_types.h>
9 #include <linux/err.h>
10 #include <linux/spinlock.h>
11 #include <linux/io.h>
12 #include <linux/bitops.h>
13 #include <linux/of_address.h>
14 #include <linux/notifier.h>
15 #include <linux/cpu.h>
16 #include <linux/syscore_ops.h>
17 #include <linux/reboot.h>
18
19 #include <asm/cacheflush.h>
20 #include <asm/hardware/cache-b15-rac.h>
21
22 extern void v7_flush_kern_cache_all(void);
23
24 /* RAC register offsets, relative to the HIF_CPU_BIUCTRL register base */
25 #define RAC_CONFIG0_REG (0x78)
26 #define RACENPREF_MASK (0x3)
27 #define RACPREFINST_SHIFT (0)
28 #define RACENINST_SHIFT (2)
29 #define RACPREFDATA_SHIFT (4)
30 #define RACENDATA_SHIFT (6)
31 #define RAC_CPU_SHIFT (8)
32 #define RACCFG_MASK (0xff)
33 #define RAC_CONFIG1_REG (0x7c)
34 /* Brahma-B15 is a quad-core only design */
35 #define B15_RAC_FLUSH_REG (0x80)
36 /* Brahma-B53 is an octo-core design */
37 #define B53_RAC_FLUSH_REG (0x84)
38 #define FLUSH_RAC (1 << 0)
39
40 /* Bitmask to enable instruction and data prefetching with a 256-bytes stride */
41 #define RAC_DATA_INST_EN_MASK (1 << RACPREFINST_SHIFT | \
42 RACENPREF_MASK << RACENINST_SHIFT | \
43 1 << RACPREFDATA_SHIFT | \
44 RACENPREF_MASK << RACENDATA_SHIFT)
45
46 #define RAC_ENABLED 0
47 /* Special state where we want to bypass the spinlock and call directly
48 * into the v7 cache maintenance operations during suspend/resume
49 */
50 #define RAC_SUSPENDED 1
51
52 static void __iomem *b15_rac_base;
53 static DEFINE_SPINLOCK(rac_lock);
54
55 static u32 rac_config0_reg;
56 static u32 rac_flush_offset;
57
58 /* Initialization flag to avoid checking for b15_rac_base, and to prevent
59 * multi-platform kernels from crashing here as well.
60 */
61 static unsigned long b15_rac_flags;
62
__b15_rac_disable(void)63 static inline u32 __b15_rac_disable(void)
64 {
65 u32 val = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
66 __raw_writel(0, b15_rac_base + RAC_CONFIG0_REG);
67 dmb();
68 return val;
69 }
70
__b15_rac_flush(void)71 static inline void __b15_rac_flush(void)
72 {
73 u32 reg;
74
75 __raw_writel(FLUSH_RAC, b15_rac_base + rac_flush_offset);
76 do {
77 /* This dmb() is required to force the Bus Interface Unit
78 * to clean outstanding writes, and forces an idle cycle
79 * to be inserted.
80 */
81 dmb();
82 reg = __raw_readl(b15_rac_base + rac_flush_offset);
83 } while (reg & FLUSH_RAC);
84 }
85
b15_rac_disable_and_flush(void)86 static inline u32 b15_rac_disable_and_flush(void)
87 {
88 u32 reg;
89
90 reg = __b15_rac_disable();
91 __b15_rac_flush();
92 return reg;
93 }
94
__b15_rac_enable(u32 val)95 static inline void __b15_rac_enable(u32 val)
96 {
97 __raw_writel(val, b15_rac_base + RAC_CONFIG0_REG);
98 /* dsb() is required here to be consistent with __flush_icache_all() */
99 dsb();
100 }
101
102 #define BUILD_RAC_CACHE_OP(name, bar) \
103 void b15_flush_##name(void) \
104 { \
105 unsigned int do_flush; \
106 u32 val = 0; \
107 \
108 if (test_bit(RAC_SUSPENDED, &b15_rac_flags)) { \
109 v7_flush_##name(); \
110 bar; \
111 return; \
112 } \
113 \
114 spin_lock(&rac_lock); \
115 do_flush = test_bit(RAC_ENABLED, &b15_rac_flags); \
116 if (do_flush) \
117 val = b15_rac_disable_and_flush(); \
118 v7_flush_##name(); \
119 if (!do_flush) \
120 bar; \
121 else \
122 __b15_rac_enable(val); \
123 spin_unlock(&rac_lock); \
124 }
125
126 #define nobarrier
127
128 /* The readahead cache present in the Brahma-B15 CPU is a special piece of
129 * hardware after the integrated L2 cache of the B15 CPU complex whose purpose
130 * is to prefetch instruction and/or data with a line size of either 64 bytes
131 * or 256 bytes. The rationale is that the data-bus of the CPU interface is
132 * optimized for 256-bytes transactions, and enabling the readahead cache
133 * provides a significant performance boost we want it enabled (typically
134 * twice the performance for a memcpy benchmark application).
135 *
136 * The readahead cache is transparent for Modified Virtual Addresses
137 * cache maintenance operations: ICIMVAU, DCIMVAC, DCCMVAC, DCCMVAU and
138 * DCCIMVAC.
139 *
140 * It is however not transparent for the following cache maintenance
141 * operations: DCISW, DCCSW, DCCISW, ICIALLUIS and ICIALLU which is precisely
142 * what we are patching here with our BUILD_RAC_CACHE_OP here.
143 */
144 BUILD_RAC_CACHE_OP(kern_cache_all, nobarrier);
145
b15_rac_enable(void)146 static void b15_rac_enable(void)
147 {
148 unsigned int cpu;
149 u32 enable = 0;
150
151 for_each_possible_cpu(cpu)
152 enable |= (RAC_DATA_INST_EN_MASK << (cpu * RAC_CPU_SHIFT));
153
154 b15_rac_disable_and_flush();
155 __b15_rac_enable(enable);
156 }
157
b15_rac_reboot_notifier(struct notifier_block * nb,unsigned long action,void * data)158 static int b15_rac_reboot_notifier(struct notifier_block *nb,
159 unsigned long action,
160 void *data)
161 {
162 /* During kexec, we are not yet migrated on the boot CPU, so we need to
163 * make sure we are SMP safe here. Once the RAC is disabled, flag it as
164 * suspended such that the hotplug notifier returns early.
165 */
166 if (action == SYS_RESTART) {
167 spin_lock(&rac_lock);
168 b15_rac_disable_and_flush();
169 clear_bit(RAC_ENABLED, &b15_rac_flags);
170 set_bit(RAC_SUSPENDED, &b15_rac_flags);
171 spin_unlock(&rac_lock);
172 }
173
174 return NOTIFY_DONE;
175 }
176
177 static struct notifier_block b15_rac_reboot_nb = {
178 .notifier_call = b15_rac_reboot_notifier,
179 };
180
181 /* The CPU hotplug case is the most interesting one, we basically need to make
182 * sure that the RAC is disabled for the entire system prior to having a CPU
183 * die, in particular prior to this dying CPU having exited the coherency
184 * domain.
185 *
186 * Once this CPU is marked dead, we can safely re-enable the RAC for the
187 * remaining CPUs in the system which are still online.
188 *
189 * Offlining a CPU is the problematic case, onlining a CPU is not much of an
190 * issue since the CPU and its cache-level hierarchy will start filling with
191 * the RAC disabled, so L1 and L2 only.
192 *
193 * In this function, we should NOT have to verify any unsafe setting/condition
194 * b15_rac_base:
195 *
196 * It is protected by the RAC_ENABLED flag which is cleared by default, and
197 * being cleared when initial procedure is done. b15_rac_base had been set at
198 * that time.
199 *
200 * RAC_ENABLED:
201 * There is a small timing windows, in b15_rac_init(), between
202 * cpuhp_setup_state_*()
203 * ...
204 * set RAC_ENABLED
205 * However, there is no hotplug activity based on the Linux booting procedure.
206 *
207 * Since we have to disable RAC for all cores, we keep RAC on as long as as
208 * possible (disable it as late as possible) to gain the cache benefit.
209 *
210 * Thus, dying/dead states are chosen here
211 *
212 * We are choosing not do disable the RAC on a per-CPU basis, here, if we did
213 * we would want to consider disabling it as early as possible to benefit the
214 * other active CPUs.
215 */
216
217 /* Running on the dying CPU */
b15_rac_dying_cpu(unsigned int cpu)218 static int b15_rac_dying_cpu(unsigned int cpu)
219 {
220 /* During kexec/reboot, the RAC is disabled via the reboot notifier
221 * return early here.
222 */
223 if (test_bit(RAC_SUSPENDED, &b15_rac_flags))
224 return 0;
225
226 spin_lock(&rac_lock);
227
228 /* Indicate that we are starting a hotplug procedure */
229 __clear_bit(RAC_ENABLED, &b15_rac_flags);
230
231 /* Disable the readahead cache and save its value to a global */
232 rac_config0_reg = b15_rac_disable_and_flush();
233
234 spin_unlock(&rac_lock);
235
236 return 0;
237 }
238
239 /* Running on a non-dying CPU */
b15_rac_dead_cpu(unsigned int cpu)240 static int b15_rac_dead_cpu(unsigned int cpu)
241 {
242 /* During kexec/reboot, the RAC is disabled via the reboot notifier
243 * return early here.
244 */
245 if (test_bit(RAC_SUSPENDED, &b15_rac_flags))
246 return 0;
247
248 spin_lock(&rac_lock);
249
250 /* And enable it */
251 __b15_rac_enable(rac_config0_reg);
252 __set_bit(RAC_ENABLED, &b15_rac_flags);
253
254 spin_unlock(&rac_lock);
255
256 return 0;
257 }
258
b15_rac_suspend(void)259 static int b15_rac_suspend(void)
260 {
261 /* Suspend the read-ahead cache oeprations, forcing our cache
262 * implementation to fallback to the regular ARMv7 calls.
263 *
264 * We are guaranteed to be running on the boot CPU at this point and
265 * with every other CPU quiesced, so setting RAC_SUSPENDED is not racy
266 * here.
267 */
268 rac_config0_reg = b15_rac_disable_and_flush();
269 set_bit(RAC_SUSPENDED, &b15_rac_flags);
270
271 return 0;
272 }
273
b15_rac_resume(void)274 static void b15_rac_resume(void)
275 {
276 /* Coming out of a S3 suspend/resume cycle, the read-ahead cache
277 * register RAC_CONFIG0_REG will be restored to its default value, make
278 * sure we re-enable it and set the enable flag, we are also guaranteed
279 * to run on the boot CPU, so not racy again.
280 */
281 __b15_rac_enable(rac_config0_reg);
282 clear_bit(RAC_SUSPENDED, &b15_rac_flags);
283 }
284
285 static struct syscore_ops b15_rac_syscore_ops = {
286 .suspend = b15_rac_suspend,
287 .resume = b15_rac_resume,
288 };
289
b15_rac_init(void)290 static int __init b15_rac_init(void)
291 {
292 struct device_node *dn, *cpu_dn;
293 int ret = 0, cpu;
294 u32 reg, en_mask = 0;
295
296 dn = of_find_compatible_node(NULL, NULL, "brcm,brcmstb-cpu-biu-ctrl");
297 if (!dn)
298 return -ENODEV;
299
300 if (WARN(num_possible_cpus() > 4, "RAC only supports 4 CPUs\n"))
301 goto out;
302
303 b15_rac_base = of_iomap(dn, 0);
304 if (!b15_rac_base) {
305 pr_err("failed to remap BIU control base\n");
306 ret = -ENOMEM;
307 goto out;
308 }
309
310 cpu_dn = of_get_cpu_node(0, NULL);
311 if (!cpu_dn) {
312 ret = -ENODEV;
313 goto out;
314 }
315
316 if (of_device_is_compatible(cpu_dn, "brcm,brahma-b15"))
317 rac_flush_offset = B15_RAC_FLUSH_REG;
318 else if (of_device_is_compatible(cpu_dn, "brcm,brahma-b53"))
319 rac_flush_offset = B53_RAC_FLUSH_REG;
320 else {
321 pr_err("Unsupported CPU\n");
322 of_node_put(cpu_dn);
323 ret = -EINVAL;
324 goto out;
325 }
326 of_node_put(cpu_dn);
327
328 ret = register_reboot_notifier(&b15_rac_reboot_nb);
329 if (ret) {
330 pr_err("failed to register reboot notifier\n");
331 iounmap(b15_rac_base);
332 goto out;
333 }
334
335 if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
336 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DEAD,
337 "arm/cache-b15-rac:dead",
338 NULL, b15_rac_dead_cpu);
339 if (ret)
340 goto out_unmap;
341
342 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING,
343 "arm/cache-b15-rac:dying",
344 NULL, b15_rac_dying_cpu);
345 if (ret)
346 goto out_cpu_dead;
347 }
348
349 if (IS_ENABLED(CONFIG_PM_SLEEP))
350 register_syscore_ops(&b15_rac_syscore_ops);
351
352 spin_lock(&rac_lock);
353 reg = __raw_readl(b15_rac_base + RAC_CONFIG0_REG);
354 for_each_possible_cpu(cpu)
355 en_mask |= ((1 << RACPREFDATA_SHIFT) << (cpu * RAC_CPU_SHIFT));
356 WARN(reg & en_mask, "Read-ahead cache not previously disabled\n");
357
358 b15_rac_enable();
359 set_bit(RAC_ENABLED, &b15_rac_flags);
360 spin_unlock(&rac_lock);
361
362 pr_info("%pOF: Broadcom Brahma-B15 readahead cache\n", dn);
363
364 goto out;
365
366 out_cpu_dead:
367 cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING);
368 out_unmap:
369 unregister_reboot_notifier(&b15_rac_reboot_nb);
370 iounmap(b15_rac_base);
371 out:
372 of_node_put(dn);
373 return ret;
374 }
375 arch_initcall(b15_rac_init);
376