root/drivers/gpu/drm/msm/adreno/a5xx_preempt.c

DEFINITIONS

1. try_preempt_state
2. set_preempt_state
3. update_wptr
4. get_next_ring
5. a5xx_preempt_timer
6. a5xx_preempt_trigger
7. a5xx_preempt_irq
8. a5xx_preempt_hw_init
9. preempt_init_ring
10. a5xx_preempt_fini
11. a5xx_preempt_init

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2017 The Linux Foundation. All rights reserved.
   3  */
   4 
   5 #include "msm_gem.h"
   6 #include "a5xx_gpu.h"
   7 
   8 /*
   9  * Try to transition the preemption state from old to new. Return
  10  * true on success or false if the original state wasn't 'old'
  11  */
  12 static inline bool try_preempt_state(struct a5xx_gpu *a5xx_gpu,
  13                 enum preempt_state old, enum preempt_state new)
  14 {
  15         enum preempt_state cur = atomic_cmpxchg(&a5xx_gpu->preempt_state,
  16                 old, new);
  17 
  18         return (cur == old);
  19 }
  20 
  21 /*
  22  * Force the preemption state to the specified state.  This is used in cases
  23  * where the current state is known and won't change
  24  */
  25 static inline void set_preempt_state(struct a5xx_gpu *gpu,
  26                 enum preempt_state new)
  27 {
  28         /*
  29          * preempt_state may be read by other cores trying to trigger a
  30          * preemption or in the interrupt handler so barriers are needed
  31          * before...
  32          */
  33         smp_mb__before_atomic();
  34         atomic_set(&gpu->preempt_state, new);
  35         /* ... and after*/
  36         smp_mb__after_atomic();
  37 }
  38 
  39 /* Write the most recent wptr for the given ring into the hardware */
  40 static inline void update_wptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
  41 {
  42         unsigned long flags;
  43         uint32_t wptr;
  44 
  45         if (!ring)
  46                 return;
  47 
  48         spin_lock_irqsave(&ring->lock, flags);
  49         wptr = get_wptr(ring);
  50         spin_unlock_irqrestore(&ring->lock, flags);
  51 
  52         gpu_write(gpu, REG_A5XX_CP_RB_WPTR, wptr);
  53 }
  54 
  55 /* Return the highest priority ringbuffer with something in it */
  56 static struct msm_ringbuffer *get_next_ring(struct msm_gpu *gpu)
  57 {
  58         unsigned long flags;
  59         int i;
  60 
  61         for (i = 0; i < gpu->nr_rings; i++) {
  62                 bool empty;
  63                 struct msm_ringbuffer *ring = gpu->rb[i];
  64 
  65                 spin_lock_irqsave(&ring->lock, flags);
  66                 empty = (get_wptr(ring) == ring->memptrs->rptr);
  67                 spin_unlock_irqrestore(&ring->lock, flags);
  68 
  69                 if (!empty)
  70                         return ring;
  71         }
  72 
  73         return NULL;
  74 }
  75 
  76 static void a5xx_preempt_timer(struct timer_list *t)
  77 {
  78         struct a5xx_gpu *a5xx_gpu = from_timer(a5xx_gpu, t, preempt_timer);
  79         struct msm_gpu *gpu = &a5xx_gpu->base.base;
  80         struct drm_device *dev = gpu->dev;
  81         struct msm_drm_private *priv = dev->dev_private;
  82 
  83         if (!try_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED, PREEMPT_FAULTED))
  84                 return;
  85 
  86         DRM_DEV_ERROR(dev->dev, "%s: preemption timed out\n", gpu->name);
  87         queue_work(priv->wq, &gpu->recover_work);
  88 }
  89 
  90 /* Try to trigger a preemption switch */
  91 void a5xx_preempt_trigger(struct msm_gpu *gpu)
  92 {
  93         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
  94         struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
  95         unsigned long flags;
  96         struct msm_ringbuffer *ring;
  97 
  98         if (gpu->nr_rings == 1)
  99                 return;
 100 
 101         /*
 102          * Try to start preemption by moving from NONE to START. If
 103          * unsuccessful, a preemption is already in flight
 104          */
 105         if (!try_preempt_state(a5xx_gpu, PREEMPT_NONE, PREEMPT_START))
 106                 return;
 107 
 108         /* Get the next ring to preempt to */
 109         ring = get_next_ring(gpu);
 110 
 111         /*
 112          * If no ring is populated or the highest priority ring is the current
 113          * one do nothing except to update the wptr to the latest and greatest
 114          */
 115         if (!ring || (a5xx_gpu->cur_ring == ring)) {
 116                 /*
 117                  * Its possible that while a preemption request is in progress
 118                  * from an irq context, a user context trying to submit might
 119                  * fail to update the write pointer, because it determines
 120                  * that the preempt state is not PREEMPT_NONE.
 121                  *
 122                  * Close the race by introducing an intermediate
 123                  * state PREEMPT_ABORT to let the submit path
 124                  * know that the ringbuffer is not going to change
 125                  * and can safely update the write pointer.
 126                  */
 127 
 128                 set_preempt_state(a5xx_gpu, PREEMPT_ABORT);
 129                 update_wptr(gpu, a5xx_gpu->cur_ring);
 130                 set_preempt_state(a5xx_gpu, PREEMPT_NONE);
 131                 return;
 132         }
 133 
 134         /* Make sure the wptr doesn't update while we're in motion */
 135         spin_lock_irqsave(&ring->lock, flags);
 136         a5xx_gpu->preempt[ring->id]->wptr = get_wptr(ring);
 137         spin_unlock_irqrestore(&ring->lock, flags);
 138 
 139         /* Set the address of the incoming preemption record */
 140         gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_LO,
 141                 REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_HI,
 142                 a5xx_gpu->preempt_iova[ring->id]);
 143 
 144         a5xx_gpu->next_ring = ring;
 145 
 146         /* Start a timer to catch a stuck preemption */
 147         mod_timer(&a5xx_gpu->preempt_timer, jiffies + msecs_to_jiffies(10000));
 148 
 149         /* Set the preemption state to triggered */
 150         set_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED);
 151 
 152         /* Make sure everything is written before hitting the button */
 153         wmb();
 154 
 155         /* And actually start the preemption */
 156         gpu_write(gpu, REG_A5XX_CP_CONTEXT_SWITCH_CNTL, 1);
 157 }
 158 
 159 void a5xx_preempt_irq(struct msm_gpu *gpu)
 160 {
 161         uint32_t status;
 162         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 163         struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
 164         struct drm_device *dev = gpu->dev;
 165         struct msm_drm_private *priv = dev->dev_private;
 166 
 167         if (!try_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED, PREEMPT_PENDING))
 168                 return;
 169 
 170         /* Delete the preemption watchdog timer */
 171         del_timer(&a5xx_gpu->preempt_timer);
 172 
 173         /*
 174          * The hardware should be setting CP_CONTEXT_SWITCH_CNTL to zero before
 175          * firing the interrupt, but there is a non zero chance of a hardware
 176          * condition or a software race that could set it again before we have a
 177          * chance to finish. If that happens, log and go for recovery
 178          */
 179         status = gpu_read(gpu, REG_A5XX_CP_CONTEXT_SWITCH_CNTL);
 180         if (unlikely(status)) {
 181                 set_preempt_state(a5xx_gpu, PREEMPT_FAULTED);
 182                 DRM_DEV_ERROR(dev->dev, "%s: Preemption failed to complete\n",
 183                         gpu->name);
 184                 queue_work(priv->wq, &gpu->recover_work);
 185                 return;
 186         }
 187 
 188         a5xx_gpu->cur_ring = a5xx_gpu->next_ring;
 189         a5xx_gpu->next_ring = NULL;
 190 
 191         update_wptr(gpu, a5xx_gpu->cur_ring);
 192 
 193         set_preempt_state(a5xx_gpu, PREEMPT_NONE);
 194 }
 195 
 196 void a5xx_preempt_hw_init(struct msm_gpu *gpu)
 197 {
 198         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 199         struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
 200         int i;
 201 
 202         /* Always come up on rb 0 */
 203         a5xx_gpu->cur_ring = gpu->rb[0];
 204 
 205         /* No preemption if we only have one ring */
 206         if (gpu->nr_rings == 1)
 207                 return;
 208 
 209         for (i = 0; i < gpu->nr_rings; i++) {
 210                 a5xx_gpu->preempt[i]->wptr = 0;
 211                 a5xx_gpu->preempt[i]->rptr = 0;
 212                 a5xx_gpu->preempt[i]->rbase = gpu->rb[i]->iova;
 213         }
 214 
 215         /* Write a 0 to signal that we aren't switching pagetables */
 216         gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_SMMU_INFO_LO,
 217                 REG_A5XX_CP_CONTEXT_SWITCH_SMMU_INFO_HI, 0);
 218 
 219         /* Reset the preemption state */
 220         set_preempt_state(a5xx_gpu, PREEMPT_NONE);
 221 }
 222 
 223 static int preempt_init_ring(struct a5xx_gpu *a5xx_gpu,
 224                 struct msm_ringbuffer *ring)
 225 {
 226         struct adreno_gpu *adreno_gpu = &a5xx_gpu->base;
 227         struct msm_gpu *gpu = &adreno_gpu->base;
 228         struct a5xx_preempt_record *ptr;
 229         struct drm_gem_object *bo = NULL;
 230         u64 iova = 0;
 231 
 232         ptr = msm_gem_kernel_new(gpu->dev,
 233                 A5XX_PREEMPT_RECORD_SIZE + A5XX_PREEMPT_COUNTER_SIZE,
 234                 MSM_BO_UNCACHED, gpu->aspace, &bo, &iova);
 235 
 236         if (IS_ERR(ptr))
 237                 return PTR_ERR(ptr);
 238 
 239         msm_gem_object_set_name(bo, "preempt");
 240 
 241         a5xx_gpu->preempt_bo[ring->id] = bo;
 242         a5xx_gpu->preempt_iova[ring->id] = iova;
 243         a5xx_gpu->preempt[ring->id] = ptr;
 244 
 245         /* Set up the defaults on the preemption record */
 246 
 247         ptr->magic = A5XX_PREEMPT_RECORD_MAGIC;
 248         ptr->info = 0;
 249         ptr->data = 0;
 250         ptr->cntl = MSM_GPU_RB_CNTL_DEFAULT;
 251         ptr->rptr_addr = rbmemptr(ring, rptr);
 252         ptr->counter = iova + A5XX_PREEMPT_RECORD_SIZE;
 253 
 254         return 0;
 255 }
 256 
 257 void a5xx_preempt_fini(struct msm_gpu *gpu)
 258 {
 259         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 260         struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
 261         int i;
 262 
 263         for (i = 0; i < gpu->nr_rings; i++)
 264                 msm_gem_kernel_put(a5xx_gpu->preempt_bo[i], gpu->aspace, true);
 265 }
 266 
 267 void a5xx_preempt_init(struct msm_gpu *gpu)
 268 {
 269         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 270         struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
 271         int i;
 272 
 273         /* No preemption if we only have one ring */
 274         if (gpu->nr_rings <= 1)
 275                 return;
 276 
 277         for (i = 0; i < gpu->nr_rings; i++) {
 278                 if (preempt_init_ring(a5xx_gpu, gpu->rb[i])) {
 279                         /*
 280                          * On any failure our adventure is over. Clean up and
 281                          * set nr_rings to 1 to force preemption off
 282                          */
 283                         a5xx_preempt_fini(gpu);
 284                         gpu->nr_rings = 1;
 285 
 286                         return;
 287                 }
 288         }
 289 
 290         timer_setup(&a5xx_gpu->preempt_timer, a5xx_preempt_timer, 0);
 291 }