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->preempt_lock, flags);
49 	wptr = get_wptr(ring);
50 	spin_unlock_irqrestore(&ring->preempt_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->preempt_lock, flags);
66 		empty = (get_wptr(ring) == ring->memptrs->rptr);
67 		spin_unlock_irqrestore(&ring->preempt_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 
82 	if (!try_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED, PREEMPT_FAULTED))
83 		return;
84 
85 	DRM_DEV_ERROR(dev->dev, "%s: preemption timed out\n", gpu->name);
86 	kthread_queue_work(gpu->worker, &gpu->recover_work);
87 }
88 
89 /* Try to trigger a preemption switch */
90 void a5xx_preempt_trigger(struct msm_gpu *gpu)
91 {
92 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
93 	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
94 	unsigned long flags;
95 	struct msm_ringbuffer *ring;
96 
97 	if (gpu->nr_rings == 1)
98 		return;
99 
100 	/*
101 	 * Try to start preemption by moving from NONE to START. If
102 	 * unsuccessful, a preemption is already in flight
103 	 */
104 	if (!try_preempt_state(a5xx_gpu, PREEMPT_NONE, PREEMPT_START))
105 		return;
106 
107 	/* Get the next ring to preempt to */
108 	ring = get_next_ring(gpu);
109 
110 	/*
111 	 * If no ring is populated or the highest priority ring is the current
112 	 * one do nothing except to update the wptr to the latest and greatest
113 	 */
114 	if (!ring || (a5xx_gpu->cur_ring == ring)) {
115 		/*
116 		 * Its possible that while a preemption request is in progress
117 		 * from an irq context, a user context trying to submit might
118 		 * fail to update the write pointer, because it determines
119 		 * that the preempt state is not PREEMPT_NONE.
120 		 *
121 		 * Close the race by introducing an intermediate
122 		 * state PREEMPT_ABORT to let the submit path
123 		 * know that the ringbuffer is not going to change
124 		 * and can safely update the write pointer.
125 		 */
126 
127 		set_preempt_state(a5xx_gpu, PREEMPT_ABORT);
128 		update_wptr(gpu, a5xx_gpu->cur_ring);
129 		set_preempt_state(a5xx_gpu, PREEMPT_NONE);
130 		return;
131 	}
132 
133 	/* Make sure the wptr doesn't update while we're in motion */
134 	spin_lock_irqsave(&ring->preempt_lock, flags);
135 	a5xx_gpu->preempt[ring->id]->wptr = get_wptr(ring);
136 	spin_unlock_irqrestore(&ring->preempt_lock, flags);
137 
138 	/* Set the address of the incoming preemption record */
139 	gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_LO,
140 		REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_HI,
141 		a5xx_gpu->preempt_iova[ring->id]);
142 
143 	a5xx_gpu->next_ring = ring;
144 
145 	/* Start a timer to catch a stuck preemption */
146 	mod_timer(&a5xx_gpu->preempt_timer, jiffies + msecs_to_jiffies(10000));
147 
148 	/* Set the preemption state to triggered */
149 	set_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED);
150 
151 	/* Make sure everything is written before hitting the button */
152 	wmb();
153 
154 	/* And actually start the preemption */
155 	gpu_write(gpu, REG_A5XX_CP_CONTEXT_SWITCH_CNTL, 1);
156 }
157 
158 void a5xx_preempt_irq(struct msm_gpu *gpu)
159 {
160 	uint32_t status;
161 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
162 	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
163 	struct drm_device *dev = gpu->dev;
164 
165 	if (!try_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED, PREEMPT_PENDING))
166 		return;
167 
168 	/* Delete the preemption watchdog timer */
169 	del_timer(&a5xx_gpu->preempt_timer);
170 
171 	/*
172 	 * The hardware should be setting CP_CONTEXT_SWITCH_CNTL to zero before
173 	 * firing the interrupt, but there is a non zero chance of a hardware
174 	 * condition or a software race that could set it again before we have a
175 	 * chance to finish. If that happens, log and go for recovery
176 	 */
177 	status = gpu_read(gpu, REG_A5XX_CP_CONTEXT_SWITCH_CNTL);
178 	if (unlikely(status)) {
179 		set_preempt_state(a5xx_gpu, PREEMPT_FAULTED);
180 		DRM_DEV_ERROR(dev->dev, "%s: Preemption failed to complete\n",
181 			gpu->name);
182 		kthread_queue_work(gpu->worker, &gpu->recover_work);
183 		return;
184 	}
185 
186 	a5xx_gpu->cur_ring = a5xx_gpu->next_ring;
187 	a5xx_gpu->next_ring = NULL;
188 
189 	update_wptr(gpu, a5xx_gpu->cur_ring);
190 
191 	set_preempt_state(a5xx_gpu, PREEMPT_NONE);
192 }
193 
194 void a5xx_preempt_hw_init(struct msm_gpu *gpu)
195 {
196 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
197 	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
198 	int i;
199 
200 	/* Always come up on rb 0 */
201 	a5xx_gpu->cur_ring = gpu->rb[0];
202 
203 	/* No preemption if we only have one ring */
204 	if (gpu->nr_rings == 1)
205 		return;
206 
207 	for (i = 0; i < gpu->nr_rings; i++) {
208 		a5xx_gpu->preempt[i]->wptr = 0;
209 		a5xx_gpu->preempt[i]->rptr = 0;
210 		a5xx_gpu->preempt[i]->rbase = gpu->rb[i]->iova;
211 	}
212 
213 	/* Write a 0 to signal that we aren't switching pagetables */
214 	gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_SMMU_INFO_LO,
215 		REG_A5XX_CP_CONTEXT_SWITCH_SMMU_INFO_HI, 0);
216 
217 	/* Reset the preemption state */
218 	set_preempt_state(a5xx_gpu, PREEMPT_NONE);
219 }
220 
221 static int preempt_init_ring(struct a5xx_gpu *a5xx_gpu,
222 		struct msm_ringbuffer *ring)
223 {
224 	struct adreno_gpu *adreno_gpu = &a5xx_gpu->base;
225 	struct msm_gpu *gpu = &adreno_gpu->base;
226 	struct a5xx_preempt_record *ptr;
227 	void *counters;
228 	struct drm_gem_object *bo = NULL, *counters_bo = NULL;
229 	u64 iova = 0, counters_iova = 0;
230 
231 	ptr = msm_gem_kernel_new(gpu->dev,
232 		A5XX_PREEMPT_RECORD_SIZE + A5XX_PREEMPT_COUNTER_SIZE,
233 		MSM_BO_WC | MSM_BO_MAP_PRIV, gpu->aspace, &bo, &iova);
234 
235 	if (IS_ERR(ptr))
236 		return PTR_ERR(ptr);
237 
238 	/* The buffer to store counters needs to be unprivileged */
239 	counters = msm_gem_kernel_new(gpu->dev,
240 		A5XX_PREEMPT_COUNTER_SIZE,
241 		MSM_BO_WC, gpu->aspace, &counters_bo, &counters_iova);
242 	if (IS_ERR(counters)) {
243 		msm_gem_kernel_put(bo, gpu->aspace);
244 		return PTR_ERR(counters);
245 	}
246 
247 	msm_gem_object_set_name(bo, "preempt");
248 	msm_gem_object_set_name(counters_bo, "preempt_counters");
249 
250 	a5xx_gpu->preempt_bo[ring->id] = bo;
251 	a5xx_gpu->preempt_counters_bo[ring->id] = counters_bo;
252 	a5xx_gpu->preempt_iova[ring->id] = iova;
253 	a5xx_gpu->preempt[ring->id] = ptr;
254 
255 	/* Set up the defaults on the preemption record */
256 
257 	ptr->magic = A5XX_PREEMPT_RECORD_MAGIC;
258 	ptr->info = 0;
259 	ptr->data = 0;
260 	ptr->cntl = MSM_GPU_RB_CNTL_DEFAULT | AXXX_CP_RB_CNTL_NO_UPDATE;
261 
262 	ptr->rptr_addr = shadowptr(a5xx_gpu, ring);
263 	ptr->counter = counters_iova;
264 
265 	return 0;
266 }
267 
268 void a5xx_preempt_fini(struct msm_gpu *gpu)
269 {
270 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
271 	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
272 	int i;
273 
274 	for (i = 0; i < gpu->nr_rings; i++) {
275 		msm_gem_kernel_put(a5xx_gpu->preempt_bo[i], gpu->aspace);
276 		msm_gem_kernel_put(a5xx_gpu->preempt_counters_bo[i], gpu->aspace);
277 	}
278 }
279 
280 void a5xx_preempt_init(struct msm_gpu *gpu)
281 {
282 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
283 	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
284 	int i;
285 
286 	/* No preemption if we only have one ring */
287 	if (gpu->nr_rings <= 1)
288 		return;
289 
290 	for (i = 0; i < gpu->nr_rings; i++) {
291 		if (preempt_init_ring(a5xx_gpu, gpu->rb[i])) {
292 			/*
293 			 * On any failure our adventure is over. Clean up and
294 			 * set nr_rings to 1 to force preemption off
295 			 */
296 			a5xx_preempt_fini(gpu);
297 			gpu->nr_rings = 1;
298 
299 			return;
300 		}
301 	}
302 
303 	timer_setup(&a5xx_gpu->preempt_timer, a5xx_preempt_timer, 0);
304 }
305