arch/arm/mm/cache-b15-rac.c

   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
  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
  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 oustanding 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
  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
  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
 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
 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 */
 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 */
 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
 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
 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
 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);