root/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_mutex.c

DEFINITIONS

1. nfp_mutex_locked
2. nfp_mutex_unlocked
3. nfp_mutex_owner
4. nfp_mutex_is_locked
5. nfp_mutex_is_unlocked
6. nfp_cpp_mutex_validate
7. nfp_cpp_mutex_init
8. nfp_cpp_mutex_alloc
9. nfp_cpp_mutex_free
10. nfp_cpp_mutex_lock
11. nfp_cpp_mutex_unlock
12. nfp_cpp_mutex_trylock
13. nfp_cpp_mutex_reclaim

   1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
   2 /* Copyright (C) 2015-2018 Netronome Systems, Inc. */
   3 
   4 #include <linux/delay.h>
   5 #include <linux/device.h>
   6 #include <linux/jiffies.h>
   7 #include <linux/types.h>
   8 #include <linux/slab.h>
   9 #include <linux/wait.h>
  10 
  11 #include "nfp_cpp.h"
  12 #include "nfp6000/nfp6000.h"
  13 
  14 struct nfp_cpp_mutex {
  15         struct nfp_cpp *cpp;
  16         int target;
  17         u16 depth;
  18         unsigned long long address;
  19         u32 key;
  20 };
  21 
  22 static u32 nfp_mutex_locked(u16 interface)
  23 {
  24         return (u32)interface << 16 | 0x000f;
  25 }
  26 
  27 static u32 nfp_mutex_unlocked(u16 interface)
  28 {
  29         return (u32)interface << 16 | 0x0000;
  30 }
  31 
  32 static u32 nfp_mutex_owner(u32 val)
  33 {
  34         return val >> 16;
  35 }
  36 
  37 static bool nfp_mutex_is_locked(u32 val)
  38 {
  39         return (val & 0xffff) == 0x000f;
  40 }
  41 
  42 static bool nfp_mutex_is_unlocked(u32 val)
  43 {
  44         return (val & 0xffff) == 0000;
  45 }
  46 
  47 /* If you need more than 65536 recursive locks, please rethink your code. */
  48 #define NFP_MUTEX_DEPTH_MAX         0xffff
  49 
  50 static int
  51 nfp_cpp_mutex_validate(u16 interface, int *target, unsigned long long address)
  52 {
  53         /* Not permitted on invalid interfaces */
  54         if (NFP_CPP_INTERFACE_TYPE_of(interface) ==
  55             NFP_CPP_INTERFACE_TYPE_INVALID)
  56                 return -EINVAL;
  57 
  58         /* Address must be 64-bit aligned */
  59         if (address & 7)
  60                 return -EINVAL;
  61 
  62         if (*target != NFP_CPP_TARGET_MU)
  63                 return -EINVAL;
  64 
  65         return 0;
  66 }
  67 
  68 /**
  69  * nfp_cpp_mutex_init() - Initialize a mutex location
  70  * @cpp:        NFP CPP handle
  71  * @target:     NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
  72  * @address:    Offset into the address space of the NFP CPP target ID
  73  * @key:        Unique 32-bit value for this mutex
  74  *
  75  * The CPP target:address must point to a 64-bit aligned location, and
  76  * will initialize 64 bits of data at the location.
  77  *
  78  * This creates the initial mutex state, as locked by this
  79  * nfp_cpp_interface().
  80  *
  81  * This function should only be called when setting up
  82  * the initial lock state upon boot-up of the system.
  83  *
  84  * Return: 0 on success, or -errno on failure
  85  */
  86 int nfp_cpp_mutex_init(struct nfp_cpp *cpp,
  87                        int target, unsigned long long address, u32 key)
  88 {
  89         const u32 muw = NFP_CPP_ID(target, 4, 0);    /* atomic_write */
  90         u16 interface = nfp_cpp_interface(cpp);
  91         int err;
  92 
  93         err = nfp_cpp_mutex_validate(interface, &target, address);
  94         if (err)
  95                 return err;
  96 
  97         err = nfp_cpp_writel(cpp, muw, address + 4, key);
  98         if (err)
  99                 return err;
 100 
 101         err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_locked(interface));
 102         if (err)
 103                 return err;
 104 
 105         return 0;
 106 }
 107 
 108 /**
 109  * nfp_cpp_mutex_alloc() - Create a mutex handle
 110  * @cpp:        NFP CPP handle
 111  * @target:     NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
 112  * @address:    Offset into the address space of the NFP CPP target ID
 113  * @key:        32-bit unique key (must match the key at this location)
 114  *
 115  * The CPP target:address must point to a 64-bit aligned location, and
 116  * reserve 64 bits of data at the location for use by the handle.
 117  *
 118  * Only target/address pairs that point to entities that support the
 119  * MU Atomic Engine's CmpAndSwap32 command are supported.
 120  *
 121  * Return:      A non-NULL struct nfp_cpp_mutex * on success, NULL on failure.
 122  */
 123 struct nfp_cpp_mutex *nfp_cpp_mutex_alloc(struct nfp_cpp *cpp, int target,
 124                                           unsigned long long address, u32 key)
 125 {
 126         const u32 mur = NFP_CPP_ID(target, 3, 0);    /* atomic_read */
 127         u16 interface = nfp_cpp_interface(cpp);
 128         struct nfp_cpp_mutex *mutex;
 129         int err;
 130         u32 tmp;
 131 
 132         err = nfp_cpp_mutex_validate(interface, &target, address);
 133         if (err)
 134                 return NULL;
 135 
 136         err = nfp_cpp_readl(cpp, mur, address + 4, &tmp);
 137         if (err < 0)
 138                 return NULL;
 139 
 140         if (tmp != key)
 141                 return NULL;
 142 
 143         mutex = kzalloc(sizeof(*mutex), GFP_KERNEL);
 144         if (!mutex)
 145                 return NULL;
 146 
 147         mutex->cpp = cpp;
 148         mutex->target = target;
 149         mutex->address = address;
 150         mutex->key = key;
 151         mutex->depth = 0;
 152 
 153         return mutex;
 154 }
 155 
 156 /**
 157  * nfp_cpp_mutex_free() - Free a mutex handle - does not alter the lock state
 158  * @mutex:      NFP CPP Mutex handle
 159  */
 160 void nfp_cpp_mutex_free(struct nfp_cpp_mutex *mutex)
 161 {
 162         kfree(mutex);
 163 }
 164 
 165 /**
 166  * nfp_cpp_mutex_lock() - Lock a mutex handle, using the NFP MU Atomic Engine
 167  * @mutex:      NFP CPP Mutex handle
 168  *
 169  * Return: 0 on success, or -errno on failure
 170  */
 171 int nfp_cpp_mutex_lock(struct nfp_cpp_mutex *mutex)
 172 {
 173         unsigned long warn_at = jiffies + NFP_MUTEX_WAIT_FIRST_WARN * HZ;
 174         unsigned long err_at = jiffies + NFP_MUTEX_WAIT_ERROR * HZ;
 175         unsigned int timeout_ms = 1;
 176         int err;
 177 
 178         /* We can't use a waitqueue here, because the unlocker
 179          * might be on a separate CPU.
 180          *
 181          * So just wait for now.
 182          */
 183         for (;;) {
 184                 err = nfp_cpp_mutex_trylock(mutex);
 185                 if (err != -EBUSY)
 186                         break;
 187 
 188                 err = msleep_interruptible(timeout_ms);
 189                 if (err != 0) {
 190                         nfp_info(mutex->cpp,
 191                                  "interrupted waiting for NFP mutex\n");
 192                         return -ERESTARTSYS;
 193                 }
 194 
 195                 if (time_is_before_eq_jiffies(warn_at)) {
 196                         warn_at = jiffies + NFP_MUTEX_WAIT_NEXT_WARN * HZ;
 197                         nfp_warn(mutex->cpp,
 198                                  "Warning: waiting for NFP mutex [depth:%hd target:%d addr:%llx key:%08x]\n",
 199                                  mutex->depth,
 200                                  mutex->target, mutex->address, mutex->key);
 201                 }
 202                 if (time_is_before_eq_jiffies(err_at)) {
 203                         nfp_err(mutex->cpp, "Error: mutex wait timed out\n");
 204                         return -EBUSY;
 205                 }
 206         }
 207 
 208         return err;
 209 }
 210 
 211 /**
 212  * nfp_cpp_mutex_unlock() - Unlock a mutex handle, using the MU Atomic Engine
 213  * @mutex:      NFP CPP Mutex handle
 214  *
 215  * Return: 0 on success, or -errno on failure
 216  */
 217 int nfp_cpp_mutex_unlock(struct nfp_cpp_mutex *mutex)
 218 {
 219         const u32 muw = NFP_CPP_ID(mutex->target, 4, 0);    /* atomic_write */
 220         const u32 mur = NFP_CPP_ID(mutex->target, 3, 0);    /* atomic_read */
 221         struct nfp_cpp *cpp = mutex->cpp;
 222         u32 key, value;
 223         u16 interface;
 224         int err;
 225 
 226         interface = nfp_cpp_interface(cpp);
 227 
 228         if (mutex->depth > 1) {
 229                 mutex->depth--;
 230                 return 0;
 231         }
 232 
 233         err = nfp_cpp_readl(mutex->cpp, mur, mutex->address + 4, &key);
 234         if (err < 0)
 235                 return err;
 236 
 237         if (key != mutex->key)
 238                 return -EPERM;
 239 
 240         err = nfp_cpp_readl(mutex->cpp, mur, mutex->address, &value);
 241         if (err < 0)
 242                 return err;
 243 
 244         if (value != nfp_mutex_locked(interface))
 245                 return -EACCES;
 246 
 247         err = nfp_cpp_writel(cpp, muw, mutex->address,
 248                              nfp_mutex_unlocked(interface));
 249         if (err < 0)
 250                 return err;
 251 
 252         mutex->depth = 0;
 253         return 0;
 254 }
 255 
 256 /**
 257  * nfp_cpp_mutex_trylock() - Attempt to lock a mutex handle
 258  * @mutex:      NFP CPP Mutex handle
 259  *
 260  * Return:      0 if the lock succeeded, -errno on failure
 261  */
 262 int nfp_cpp_mutex_trylock(struct nfp_cpp_mutex *mutex)
 263 {
 264         const u32 muw = NFP_CPP_ID(mutex->target, 4, 0);    /* atomic_write */
 265         const u32 mus = NFP_CPP_ID(mutex->target, 5, 3);    /* test_set_imm */
 266         const u32 mur = NFP_CPP_ID(mutex->target, 3, 0);    /* atomic_read */
 267         struct nfp_cpp *cpp = mutex->cpp;
 268         u32 key, value, tmp;
 269         int err;
 270 
 271         if (mutex->depth > 0) {
 272                 if (mutex->depth == NFP_MUTEX_DEPTH_MAX)
 273                         return -E2BIG;
 274                 mutex->depth++;
 275                 return 0;
 276         }
 277 
 278         /* Verify that the lock marker is not damaged */
 279         err = nfp_cpp_readl(cpp, mur, mutex->address + 4, &key);
 280         if (err < 0)
 281                 return err;
 282 
 283         if (key != mutex->key)
 284                 return -EPERM;
 285 
 286         /* Compare against the unlocked state, and if true,
 287          * write the interface id into the top 16 bits, and
 288          * mark as locked.
 289          */
 290         value = nfp_mutex_locked(nfp_cpp_interface(cpp));
 291 
 292         /* We use test_set_imm here, as it implies a read
 293          * of the current state, and sets the bits in the
 294          * bytemask of the command to 1s. Since the mutex
 295          * is guaranteed to be 64-bit aligned, the bytemask
 296          * of this 32-bit command is ensured to be 8'b00001111,
 297          * which implies that the lower 4 bits will be set to
 298          * ones regardless of the initial state.
 299          *
 300          * Since this is a 'Readback' operation, with no Pull
 301          * data, we can treat this as a normal Push (read)
 302          * atomic, which returns the original value.
 303          */
 304         err = nfp_cpp_readl(cpp, mus, mutex->address, &tmp);
 305         if (err < 0)
 306                 return err;
 307 
 308         /* Was it unlocked? */
 309         if (nfp_mutex_is_unlocked(tmp)) {
 310                 /* The read value can only be 0x....0000 in the unlocked state.
 311                  * If there was another contending for this lock, then
 312                  * the lock state would be 0x....000f
 313                  */
 314 
 315                 /* Write our owner ID into the lock
 316                  * While not strictly necessary, this helps with
 317                  * debug and bookkeeping.
 318                  */
 319                 err = nfp_cpp_writel(cpp, muw, mutex->address, value);
 320                 if (err < 0)
 321                         return err;
 322 
 323                 mutex->depth = 1;
 324                 return 0;
 325         }
 326 
 327         return nfp_mutex_is_locked(tmp) ? -EBUSY : -EINVAL;
 328 }
 329 
 330 /**
 331  * nfp_cpp_mutex_reclaim() - Unlock mutex if held by local endpoint
 332  * @cpp:        NFP CPP handle
 333  * @target:     NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
 334  * @address:    Offset into the address space of the NFP CPP target ID
 335  *
 336  * Release lock if held by local system.  Extreme care is advised, call only
 337  * when no local lock users can exist.
 338  *
 339  * Return:      0 if the lock was OK, 1 if locked by us, -errno on invalid mutex
 340  */
 341 int nfp_cpp_mutex_reclaim(struct nfp_cpp *cpp, int target,
 342                           unsigned long long address)
 343 {
 344         const u32 mur = NFP_CPP_ID(target, 3, 0);       /* atomic_read */
 345         const u32 muw = NFP_CPP_ID(target, 4, 0);       /* atomic_write */
 346         u16 interface = nfp_cpp_interface(cpp);
 347         int err;
 348         u32 tmp;
 349 
 350         err = nfp_cpp_mutex_validate(interface, &target, address);
 351         if (err)
 352                 return err;
 353 
 354         /* Check lock */
 355         err = nfp_cpp_readl(cpp, mur, address, &tmp);
 356         if (err < 0)
 357                 return err;
 358 
 359         if (nfp_mutex_is_unlocked(tmp) || nfp_mutex_owner(tmp) != interface)
 360                 return 0;
 361 
 362         /* Bust the lock */
 363         err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_unlocked(interface));
 364         if (err < 0)
 365                 return err;
 366 
 367         return 1;
 368 }