drm/msm: Implement preemption for A5XX targets

Implement preemption for A5XX targets - this allows multiple
ringbuffers for different priorities with automatic preemption
of a lower priority ringbuffer if a higher one is ready.

Signed-off-by: Jordan Crouse <[e-mail]>
Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/Makefile

···
 	adreno/a4xx_gpu.o \
 	adreno/a5xx_gpu.o \
 	adreno/a5xx_power.o \
+	adreno/a5xx_preempt.o \
 	hdmi/hdmi.o \
 	hdmi/hdmi_audio.o \
 	hdmi/hdmi_bridge.o \

drivers/gpu/drm/msm/adreno/a5xx_gpu.c

···
 	return ret;
 }
 
+static void a5xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	uint32_t wptr;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ring->lock, flags);
+
+	/* Copy the shadow to the actual register */
+	ring->cur = ring->next;
+
+	/* Make sure to wrap wptr if we need to */
+	wptr = get_wptr(ring);
+
+	spin_unlock_irqrestore(&ring->lock, flags);
+
+	/* Make sure everything is posted before making a decision */
+	mb();
+
+	/* Update HW if this is the current ring and we are not in preempt */
+	if (a5xx_gpu->cur_ring == ring && !a5xx_in_preempt(a5xx_gpu))
+		gpu_write(gpu, REG_A5XX_CP_RB_WPTR, wptr);
+}
+
 static void a5xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit,
 	struct msm_file_private *ctx)
 {
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
 	struct msm_drm_private *priv = gpu->dev->dev_private;
 	struct msm_ringbuffer *ring = submit->ring;
 	unsigned int i, ibs = 0;
 
+	OUT_PKT7(ring, CP_PREEMPT_ENABLE_GLOBAL, 1);
+	OUT_RING(ring, 0x02);
+
+	/* Turn off protected mode to write to special registers */
+	OUT_PKT7(ring, CP_SET_PROTECTED_MODE, 1);
+	OUT_RING(ring, 0);
+
+	/* Set the save preemption record for the ring/command */
+	OUT_PKT4(ring, REG_A5XX_CP_CONTEXT_SWITCH_SAVE_ADDR_LO, 2);
+	OUT_RING(ring, lower_32_bits(a5xx_gpu->preempt_iova[submit->ring->id]));
+	OUT_RING(ring, upper_32_bits(a5xx_gpu->preempt_iova[submit->ring->id]));
+
+	/* Turn back on protected mode */
+	OUT_PKT7(ring, CP_SET_PROTECTED_MODE, 1);
+	OUT_RING(ring, 1);
+
+	/* Enable local preemption for finegrain preemption */
+	OUT_PKT7(ring, CP_PREEMPT_ENABLE_GLOBAL, 1);
+	OUT_RING(ring, 0x02);
+
+	/* Allow CP_CONTEXT_SWITCH_YIELD packets in the IB2 */
+	OUT_PKT7(ring, CP_YIELD_ENABLE, 1);
+	OUT_RING(ring, 0x02);
+
+	/* Submit the commands */
 	for (i = 0; i < submit->nr_cmds; i++) {
 		switch (submit->cmd[i].type) {
 		case MSM_SUBMIT_CMD_IB_TARGET_BUF:
···
 		}
 	}
 
+	/*
+	 * Write the render mode to NULL (0) to indicate to the CP that the IBs
+	 * are done rendering - otherwise a lucky preemption would start
+	 * replaying from the last checkpoint
+	 */
+	OUT_PKT7(ring, CP_SET_RENDER_MODE, 5);
+	OUT_RING(ring, 0);
+	OUT_RING(ring, 0);
+	OUT_RING(ring, 0);
+	OUT_RING(ring, 0);
+	OUT_RING(ring, 0);
+
+	/* Turn off IB level preemptions */
+	OUT_PKT7(ring, CP_YIELD_ENABLE, 1);
+	OUT_RING(ring, 0x01);
+
+	/* Write the fence to the scratch register */
 	OUT_PKT4(ring, REG_A5XX_CP_SCRATCH_REG(2), 1);
 	OUT_RING(ring, submit->seqno);
 
+	/*
+	 * Execute a CACHE_FLUSH_TS event. This will ensure that the
+	 * timestamp is written to the memory and then triggers the interrupt
+	 */
 	OUT_PKT7(ring, CP_EVENT_WRITE, 4);
 	OUT_RING(ring, CACHE_FLUSH_TS | (1 << 31));
 	OUT_RING(ring, lower_32_bits(rbmemptr(ring, fence)));
 	OUT_RING(ring, upper_32_bits(rbmemptr(ring, fence)));
 	OUT_RING(ring, submit->seqno);
 
-	gpu->funcs->flush(gpu, ring);
+	/* Yield the floor on command completion */
+	OUT_PKT7(ring, CP_CONTEXT_SWITCH_YIELD, 4);
+	/*
+	 * If dword[2:1] are non zero, they specify an address for the CP to
+	 * write the value of dword[3] to on preemption complete. Write 0 to
+	 * skip the write
+	 */
+	OUT_RING(ring, 0x00);
+	OUT_RING(ring, 0x00);
+	/* Data value - not used if the address above is 0 */
+	OUT_RING(ring, 0x01);
+	/* Set bit 0 to trigger an interrupt on preempt complete */
+	OUT_RING(ring, 0x01);
+
+	a5xx_flush(gpu, ring);
+
+	/* Check to see if we need to start preemption */
+	a5xx_preempt_trigger(gpu);
 }
 
 static const struct {
···
 	return a5xx_idle(gpu, ring) ? 0 : -EINVAL;
 }
 
+static int a5xx_preempt_start(struct msm_gpu *gpu)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	struct msm_ringbuffer *ring = gpu->rb[0];
+
+	if (gpu->nr_rings == 1)
+		return 0;
+
+	/* Turn off protected mode to write to special registers */
+	OUT_PKT7(ring, CP_SET_PROTECTED_MODE, 1);
+	OUT_RING(ring, 0);
+
+	/* Set the save preemption record for the ring/command */
+	OUT_PKT4(ring, REG_A5XX_CP_CONTEXT_SWITCH_SAVE_ADDR_LO, 2);
+	OUT_RING(ring, lower_32_bits(a5xx_gpu->preempt_iova[ring->id]));
+	OUT_RING(ring, upper_32_bits(a5xx_gpu->preempt_iova[ring->id]));
+
+	/* Turn back on protected mode */
+	OUT_PKT7(ring, CP_SET_PROTECTED_MODE, 1);
+	OUT_RING(ring, 1);
+
+	OUT_PKT7(ring, CP_PREEMPT_ENABLE_GLOBAL, 1);
+	OUT_RING(ring, 0x00);
+
+	OUT_PKT7(ring, CP_PREEMPT_ENABLE_LOCAL, 1);
+	OUT_RING(ring, 0x01);
+
+	OUT_PKT7(ring, CP_YIELD_ENABLE, 1);
+	OUT_RING(ring, 0x01);
+
+	/* Yield the floor on command completion */
+	OUT_PKT7(ring, CP_CONTEXT_SWITCH_YIELD, 4);
+	OUT_RING(ring, 0x00);
+	OUT_RING(ring, 0x00);
+	OUT_RING(ring, 0x01);
+	OUT_RING(ring, 0x01);
+
+	gpu->funcs->flush(gpu, ring);
+
+	return a5xx_idle(gpu, ring) ? 0 : -EINVAL;
+}
+
+
 static struct drm_gem_object *a5xx_ucode_load_bo(struct msm_gpu *gpu,
 		const struct firmware *fw, u64 *iova)
 {
···
 	  A5XX_RBBM_INT_0_MASK_RBBM_ATB_ASYNC_OVERFLOW | \
 	  A5XX_RBBM_INT_0_MASK_CP_HW_ERROR | \
 	  A5XX_RBBM_INT_0_MASK_MISC_HANG_DETECT | \
+	  A5XX_RBBM_INT_0_MASK_CP_SW | \
 	  A5XX_RBBM_INT_0_MASK_CP_CACHE_FLUSH_TS | \
 	  A5XX_RBBM_INT_0_MASK_UCHE_OOB_ACCESS | \
 	  A5XX_RBBM_INT_0_MASK_GPMU_VOLTAGE_DROOP)
···
 	if (ret)
 		return ret;
 
+	a5xx_preempt_hw_init(gpu);
+
 	a5xx_gpmu_ucode_init(gpu);
 
 	ret = a5xx_ucode_init(gpu);
···
 		gpu_write(gpu, REG_A5XX_RBBM_SECVID_TRUST_CNTL, 0x0);
 	}
 
+	/* Last step - yield the ringbuffer */
+	a5xx_preempt_start(gpu);
+
 	return 0;
 }
 
···
 	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
 
 	DBG("%s", gpu->name);
+
+	a5xx_preempt_fini(gpu);
 
 	if (a5xx_gpu->pm4_bo) {
 		if (a5xx_gpu->pm4_iova)
···
 
 bool a5xx_idle(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
 {
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+
+	if (ring != a5xx_gpu->cur_ring) {
+		WARN(1, "Tried to idle a non-current ringbuffer\n");
+		return false;
+	}
+
 	/* wait for CP to drain ringbuffer: */
 	if (!adreno_idle(gpu, ring))
 		return false;
···
 	if (status & A5XX_RBBM_INT_0_MASK_GPMU_VOLTAGE_DROOP)
 		a5xx_gpmu_err_irq(gpu);
 
-	if (status & A5XX_RBBM_INT_0_MASK_CP_CACHE_FLUSH_TS)
+	if (status & A5XX_RBBM_INT_0_MASK_CP_CACHE_FLUSH_TS) {
+		a5xx_preempt_trigger(gpu);
 		msm_gpu_retire(gpu);
+	}
+
+	if (status & A5XX_RBBM_INT_0_MASK_CP_SW)
+		a5xx_preempt_irq(gpu);
 
 	return IRQ_HANDLED;
 }
···
 }
 #endif
 
+static struct msm_ringbuffer *a5xx_active_ring(struct msm_gpu *gpu)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+
+	return a5xx_gpu->cur_ring;
+}
+
 static const struct adreno_gpu_funcs funcs = {
 	.base = {
 		.get_param = adreno_get_param,
···
 		.pm_resume = a5xx_pm_resume,
 		.recover = a5xx_recover,
 		.submit = a5xx_submit,
-		.flush = adreno_flush,
-		.active_ring = adreno_active_ring,
+		.flush = a5xx_flush,
+		.active_ring = a5xx_active_ring,
 		.irq = a5xx_irq,
 		.destroy = a5xx_destroy,
 #ifdef CONFIG_DEBUG_FS
···
 
 	a5xx_gpu->lm_leakage = 0x4E001A;
 
-	ret = adreno_gpu_init(dev, pdev, adreno_gpu, &funcs, 1);
+	ret = adreno_gpu_init(dev, pdev, adreno_gpu, &funcs, 4);
 	if (ret) {
 		a5xx_destroy(&(a5xx_gpu->base.base));
 		return ERR_PTR(ret);
···
 
 	if (gpu->aspace)
 		msm_mmu_set_fault_handler(gpu->aspace->mmu, gpu, a5xx_fault_handler);
+
+	/* Set up the preemption specific bits and pieces for each ringbuffer */
+	a5xx_preempt_init(gpu);
 
 	return gpu;
 }

drivers/gpu/drm/msm/adreno/a5xx_gpu.h

···
-/* Copyright (c) 2016 The Linux Foundation. All rights reserved.
+/* Copyright (c) 2016-2017 The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
···
 	uint32_t gpmu_dwords;
 
 	uint32_t lm_leakage;
+
+	struct msm_ringbuffer *cur_ring;
+	struct msm_ringbuffer *next_ring;
+
+	struct drm_gem_object *preempt_bo[MSM_GPU_MAX_RINGS];
+	struct a5xx_preempt_record *preempt[MSM_GPU_MAX_RINGS];
+	uint64_t preempt_iova[MSM_GPU_MAX_RINGS];
+
+	atomic_t preempt_state;
+	struct timer_list preempt_timer;
 };
 
 #define to_a5xx_gpu(x) container_of(x, struct a5xx_gpu, base)
+
+/*
+ * In order to do lockless preemption we use a simple state machine to progress
+ * through the process.
+ *
+ * PREEMPT_NONE - no preemption in progress.  Next state START.
+ * PREEMPT_START - The trigger is evaulating if preemption is possible. Next
+ * states: TRIGGERED, NONE
+ * PREEMPT_ABORT - An intermediate state before moving back to NONE. Next
+ * state: NONE.
+ * PREEMPT_TRIGGERED: A preemption has been executed on the hardware. Next
+ * states: FAULTED, PENDING
+ * PREEMPT_FAULTED: A preemption timed out (never completed). This will trigger
+ * recovery.  Next state: N/A
+ * PREEMPT_PENDING: Preemption complete interrupt fired - the callback is
+ * checking the success of the operation. Next state: FAULTED, NONE.
+ */
+
+enum preempt_state {
+	PREEMPT_NONE = 0,
+	PREEMPT_START,
+	PREEMPT_ABORT,
+	PREEMPT_TRIGGERED,
+	PREEMPT_FAULTED,
+	PREEMPT_PENDING,
+};
+
+/*
+ * struct a5xx_preempt_record is a shared buffer between the microcode and the
+ * CPU to store the state for preemption. The record itself is much larger
+ * (64k) but most of that is used by the CP for storage.
+ *
+ * There is a preemption record assigned per ringbuffer. When the CPU triggers a
+ * preemption, it fills out the record with the useful information (wptr, ring
+ * base, etc) and the microcode uses that information to set up the CP following
+ * the preemption.  When a ring is switched out, the CP will save the ringbuffer
+ * state back to the record. In this way, once the records are properly set up
+ * the CPU can quickly switch back and forth between ringbuffers by only
+ * updating a few registers (often only the wptr).
+ *
+ * These are the CPU aware registers in the record:
+ * @magic: Must always be 0x27C4BAFC
+ * @info: Type of the record - written 0 by the CPU, updated by the CP
+ * @data: Data field from SET_RENDER_MODE or a checkpoint. Written and used by
+ * the CP
+ * @cntl: Value of RB_CNTL written by CPU, save/restored by CP
+ * @rptr: Value of RB_RPTR written by CPU, save/restored by CP
+ * @wptr: Value of RB_WPTR written by CPU, save/restored by CP
+ * @rptr_addr: Value of RB_RPTR_ADDR written by CPU, save/restored by CP
+ * @rbase: Value of RB_BASE written by CPU, save/restored by CP
+ * @counter: GPU address of the storage area for the performance counters
+ */
+struct a5xx_preempt_record {
+	uint32_t magic;
+	uint32_t info;
+	uint32_t data;
+	uint32_t cntl;
+	uint32_t rptr;
+	uint32_t wptr;
+	uint64_t rptr_addr;
+	uint64_t rbase;
+	uint64_t counter;
+};
+
+/* Magic identifier for the preemption record */
+#define A5XX_PREEMPT_RECORD_MAGIC 0x27C4BAFCUL
+
+/*
+ * Even though the structure above is only a few bytes, we need a full 64k to
+ * store the entire preemption record from the CP
+ */
+#define A5XX_PREEMPT_RECORD_SIZE (64 * 1024)
+
+/*
+ * The preemption counter block is a storage area for the value of the
+ * preemption counters that are saved immediately before context switch. We
+ * append it on to the end of the allocation for the preemption record.
+ */
+#define A5XX_PREEMPT_COUNTER_SIZE (16 * 4)
+
 
 int a5xx_power_init(struct msm_gpu *gpu);
 void a5xx_gpmu_ucode_init(struct msm_gpu *gpu);
···
 
 bool a5xx_idle(struct msm_gpu *gpu, struct msm_ringbuffer *ring);
 void a5xx_set_hwcg(struct msm_gpu *gpu, bool state);
+
+void a5xx_preempt_init(struct msm_gpu *gpu);
+void a5xx_preempt_hw_init(struct msm_gpu *gpu);
+void a5xx_preempt_trigger(struct msm_gpu *gpu);
+void a5xx_preempt_irq(struct msm_gpu *gpu);
+void a5xx_preempt_fini(struct msm_gpu *gpu);
+
+/* Return true if we are in a preempt state */
+static inline bool a5xx_in_preempt(struct a5xx_gpu *a5xx_gpu)
+{
+	int preempt_state = atomic_read(&a5xx_gpu->preempt_state);
+
+	return !(preempt_state == PREEMPT_NONE ||
+			preempt_state == PREEMPT_ABORT);
+}
 
 #endif /* __A5XX_GPU_H__ */

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

···
+/* Copyright (c) 2017 The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include "msm_gem.h"
+#include "a5xx_gpu.h"
+
+/*
+ * Try to transition the preemption state from old to new. Return
+ * true on success or false if the original state wasn't 'old'
+ */
+static inline bool try_preempt_state(struct a5xx_gpu *a5xx_gpu,
+		enum preempt_state old, enum preempt_state new)
+{
+	enum preempt_state cur = atomic_cmpxchg(&a5xx_gpu->preempt_state,
+		old, new);
+
+	return (cur == old);
+}
+
+/*
+ * Force the preemption state to the specified state.  This is used in cases
+ * where the current state is known and won't change
+ */
+static inline void set_preempt_state(struct a5xx_gpu *gpu,
+		enum preempt_state new)
+{
+	/*
+	 * preempt_state may be read by other cores trying to trigger a
+	 * preemption or in the interrupt handler so barriers are needed
+	 * before...
+	 */
+	smp_mb__before_atomic();
+	atomic_set(&gpu->preempt_state, new);
+	/* ... and after*/
+	smp_mb__after_atomic();
+}
+
+/* Write the most recent wptr for the given ring into the hardware */
+static inline void update_wptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
+{
+	unsigned long flags;
+	uint32_t wptr;
+
+	if (!ring)
+		return;
+
+	spin_lock_irqsave(&ring->lock, flags);
+	wptr = get_wptr(ring);
+	spin_unlock_irqrestore(&ring->lock, flags);
+
+	gpu_write(gpu, REG_A5XX_CP_RB_WPTR, wptr);
+}
+
+/* Return the highest priority ringbuffer with something in it */
+static struct msm_ringbuffer *get_next_ring(struct msm_gpu *gpu)
+{
+	unsigned long flags;
+	int i;
+
+	for (i = 0; i < gpu->nr_rings; i++) {
+		bool empty;
+		struct msm_ringbuffer *ring = gpu->rb[i];
+
+		spin_lock_irqsave(&ring->lock, flags);
+		empty = (get_wptr(ring) == ring->memptrs->rptr);
+		spin_unlock_irqrestore(&ring->lock, flags);
+
+		if (!empty)
+			return ring;
+	}
+
+	return NULL;
+}
+
+static void a5xx_preempt_timer(unsigned long data)
+{
+	struct a5xx_gpu *a5xx_gpu = (struct a5xx_gpu *) data;
+	struct msm_gpu *gpu = &a5xx_gpu->base.base;
+	struct drm_device *dev = gpu->dev;
+	struct msm_drm_private *priv = dev->dev_private;
+
+	if (!try_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED, PREEMPT_FAULTED))
+		return;
+
+	dev_err(dev->dev, "%s: preemption timed out\n", gpu->name);
+	queue_work(priv->wq, &gpu->recover_work);
+}
+
+/* Try to trigger a preemption switch */
+void a5xx_preempt_trigger(struct msm_gpu *gpu)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	unsigned long flags;
+	struct msm_ringbuffer *ring;
+
+	if (gpu->nr_rings == 1)
+		return;
+
+	/*
+	 * Try to start preemption by moving from NONE to START. If
+	 * unsuccessful, a preemption is already in flight
+	 */
+	if (!try_preempt_state(a5xx_gpu, PREEMPT_NONE, PREEMPT_START))
+		return;
+
+	/* Get the next ring to preempt to */
+	ring = get_next_ring(gpu);
+
+	/*
+	 * If no ring is populated or the highest priority ring is the current
+	 * one do nothing except to update the wptr to the latest and greatest
+	 */
+	if (!ring || (a5xx_gpu->cur_ring == ring)) {
+		/*
+		 * Its possible that while a preemption request is in progress
+		 * from an irq context, a user context trying to submit might
+		 * fail to update the write pointer, because it determines
+		 * that the preempt state is not PREEMPT_NONE.
+		 *
+		 * Close the race by introducing an intermediate
+		 * state PREEMPT_ABORT to let the submit path
+		 * know that the ringbuffer is not going to change
+		 * and can safely update the write pointer.
+		 */
+
+		set_preempt_state(a5xx_gpu, PREEMPT_ABORT);
+		update_wptr(gpu, a5xx_gpu->cur_ring);
+		set_preempt_state(a5xx_gpu, PREEMPT_NONE);
+		return;
+	}
+
+	/* Make sure the wptr doesn't update while we're in motion */
+	spin_lock_irqsave(&ring->lock, flags);
+	a5xx_gpu->preempt[ring->id]->wptr = get_wptr(ring);
+	spin_unlock_irqrestore(&ring->lock, flags);
+
+	/* Set the address of the incoming preemption record */
+	gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_LO,
+		REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_HI,
+		a5xx_gpu->preempt_iova[ring->id]);
+
+	a5xx_gpu->next_ring = ring;
+
+	/* Start a timer to catch a stuck preemption */
+	mod_timer(&a5xx_gpu->preempt_timer, jiffies + msecs_to_jiffies(10000));
+
+	/* Set the preemption state to triggered */
+	set_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED);
+
+	/* Make sure everything is written before hitting the button */
+	wmb();
+
+	/* And actually start the preemption */
+	gpu_write(gpu, REG_A5XX_CP_CONTEXT_SWITCH_CNTL, 1);
+}
+
+void a5xx_preempt_irq(struct msm_gpu *gpu)
+{
+	uint32_t status;
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	struct drm_device *dev = gpu->dev;
+	struct msm_drm_private *priv = dev->dev_private;
+
+	if (!try_preempt_state(a5xx_gpu, PREEMPT_TRIGGERED, PREEMPT_PENDING))
+		return;
+
+	/* Delete the preemption watchdog timer */
+	del_timer(&a5xx_gpu->preempt_timer);
+
+	/*
+	 * The hardware should be setting CP_CONTEXT_SWITCH_CNTL to zero before
+	 * firing the interrupt, but there is a non zero chance of a hardware
+	 * condition or a software race that could set it again before we have a
+	 * chance to finish. If that happens, log and go for recovery
+	 */
+	status = gpu_read(gpu, REG_A5XX_CP_CONTEXT_SWITCH_CNTL);
+	if (unlikely(status)) {
+		set_preempt_state(a5xx_gpu, PREEMPT_FAULTED);
+		dev_err(dev->dev, "%s: Preemption failed to complete\n",
+			gpu->name);
+		queue_work(priv->wq, &gpu->recover_work);
+		return;
+	}
+
+	a5xx_gpu->cur_ring = a5xx_gpu->next_ring;
+	a5xx_gpu->next_ring = NULL;
+
+	update_wptr(gpu, a5xx_gpu->cur_ring);
+
+	set_preempt_state(a5xx_gpu, PREEMPT_NONE);
+}
+
+void a5xx_preempt_hw_init(struct msm_gpu *gpu)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	int i;
+
+	for (i = 0; i < gpu->nr_rings; i++) {
+		a5xx_gpu->preempt[i]->wptr = 0;
+		a5xx_gpu->preempt[i]->rptr = 0;
+		a5xx_gpu->preempt[i]->rbase = gpu->rb[i]->iova;
+	}
+
+	/* Write a 0 to signal that we aren't switching pagetables */
+	gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_SMMU_INFO_LO,
+		REG_A5XX_CP_CONTEXT_SWITCH_SMMU_INFO_HI, 0);
+
+	/* Reset the preemption state */
+	set_preempt_state(a5xx_gpu, PREEMPT_NONE);
+
+	/* Always come up on rb 0 */
+	a5xx_gpu->cur_ring = gpu->rb[0];
+}
+
+static int preempt_init_ring(struct a5xx_gpu *a5xx_gpu,
+		struct msm_ringbuffer *ring)
+{
+	struct adreno_gpu *adreno_gpu = &a5xx_gpu->base;
+	struct msm_gpu *gpu = &adreno_gpu->base;
+	struct a5xx_preempt_record *ptr;
+	struct drm_gem_object *bo = NULL;
+	u64 iova = 0;
+
+	ptr = msm_gem_kernel_new(gpu->dev,
+		A5XX_PREEMPT_RECORD_SIZE + A5XX_PREEMPT_COUNTER_SIZE,
+		MSM_BO_UNCACHED, gpu->aspace, &bo, &iova);
+
+	if (IS_ERR(ptr))
+		return PTR_ERR(ptr);
+
+	a5xx_gpu->preempt_bo[ring->id] = bo;
+	a5xx_gpu->preempt_iova[ring->id] = iova;
+	a5xx_gpu->preempt[ring->id] = ptr;
+
+	/* Set up the defaults on the preemption record */
+
+	ptr->magic = A5XX_PREEMPT_RECORD_MAGIC;
+	ptr->info = 0;
+	ptr->data = 0;
+	ptr->cntl = MSM_GPU_RB_CNTL_DEFAULT;
+	ptr->rptr_addr = rbmemptr(ring, rptr);
+	ptr->counter = iova + A5XX_PREEMPT_RECORD_SIZE;
+
+	return 0;
+}
+
+void a5xx_preempt_fini(struct msm_gpu *gpu)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	int i;
+
+	for (i = 0; i < gpu->nr_rings; i++) {
+		if (!a5xx_gpu->preempt_bo[i])
+			continue;
+
+		msm_gem_put_vaddr(a5xx_gpu->preempt_bo[i]);
+
+		if (a5xx_gpu->preempt_iova[i])
+			msm_gem_put_iova(a5xx_gpu->preempt_bo[i], gpu->aspace);
+
+		drm_gem_object_unreference(a5xx_gpu->preempt_bo[i]);
+		a5xx_gpu->preempt_bo[i] = NULL;
+	}
+}
+
+void a5xx_preempt_init(struct msm_gpu *gpu)
+{
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	int i;
+
+	/* No preemption if we only have one ring */
+	if (gpu->nr_rings <= 1)
+		return;
+
+	for (i = 0; i < gpu->nr_rings; i++) {
+		if (preempt_init_ring(a5xx_gpu, gpu->rb[i])) {
+			/*
+			 * On any failure our adventure is over. Clean up and
+			 * set nr_rings to 1 to force preemption off
+			 */
+			a5xx_preempt_fini(gpu);
+			gpu->nr_rings = 1;
+
+			return;
+		}
+	}
+
+	setup_timer(&a5xx_gpu->preempt_timer, a5xx_preempt_timer,
+		(unsigned long) a5xx_gpu);
+}

drivers/gpu/drm/msm/adreno/adreno_gpu.c

···
 	return 0;
 }
 
-static uint32_t get_wptr(struct msm_ringbuffer *ring)
-{
-	return ring->cur - ring->start;
-}
-
 /* Use this helper to read rptr, since a430 doesn't update rptr in memory */
 static uint32_t get_rptr(struct adreno_gpu *adreno_gpu,
 		struct msm_ringbuffer *ring)
···
 		case MSM_SUBMIT_CMD_BUF:
 			OUT_PKT3(ring, adreno_is_a430(adreno_gpu) ?
 				CP_INDIRECT_BUFFER_PFE : CP_INDIRECT_BUFFER_PFD, 2);
-			OUT_RING(ring, submit->cmd[i].iova);
+			OUT_RING(ring, lower_32_bits(submit->cmd[i].iova));
 			OUT_RING(ring, submit->cmd[i].size);
 			OUT_PKT2(ring);
 			break;
···
 	 * to account for the possibility that the last command fit exactly into
 	 * the ringbuffer and rb->next hasn't wrapped to zero yet
 	 */
-	wptr = (ring->cur - ring->start) % (MSM_GPU_RINGBUFFER_SZ >> 2);
+	wptr = get_wptr(ring);
 
 	/* ensure writes to ringbuffer have hit system memory: */
 	mb();
···
 		return true;
 
 	/* TODO maybe we need to reset GPU here to recover from hang? */
-	DRM_ERROR("%s: timeout waiting to drain ringbuffer %d!\n", gpu->name,
-		ring->id);
+	DRM_ERROR("%s: timeout waiting to drain ringbuffer %d rptr/wptr = %X/%X\n",
+		gpu->name, ring->id, get_rptr(adreno_gpu, ring), wptr);
+
 	return false;
 }
 

drivers/gpu/drm/msm/adreno/adreno_gpu.h

···
  * Copyright (C) 2013 Red Hat
  * Author: Rob Clark <[e-mail]>
  *
- * Copyright (c) 2014 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2014,2017 The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 as published by
···
 {
 	adreno_gpu_write(gpu, lo, lower_32_bits(data));
 	adreno_gpu_write(gpu, hi, upper_32_bits(data));
+}
+
+static inline uint32_t get_wptr(struct msm_ringbuffer *ring)
+{
+	return (ring->cur - ring->start) % (MSM_GPU_RINGBUFFER_SZ >> 2);
 }
 
 /*

drivers/gpu/drm/msm/msm_drv.h

···
 	spinlock_t lock;
 };
 
-#define MSM_GPU_MAX_RINGS 1
+#define MSM_GPU_MAX_RINGS 4
 
 struct msm_drm_private {
 

drivers/gpu/drm/msm/msm_gpu.c

···
 		 * Replay all remaining submits starting with highest priority
 		 * ring
 		 */
-
-		for (i = gpu->nr_rings - 1; i >= 0; i--) {
+		for (i = 0; i < gpu->nr_rings; i++) {
 			struct msm_ringbuffer *ring = gpu->rb[i];
 
 			list_for_each_entry(submit, &ring->submits, node)
···
 	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
 
 	/* Retire the commits starting with highest priority */
-	for (i = gpu->nr_rings - 1; i >= 0; i--) {
+	for (i = 0; i < gpu->nr_rings; i++) {
 		struct msm_ringbuffer *ring = gpu->rb[i];
 
 		list_for_each_entry_safe(submit, tmp, &ring->submits, node) {

drivers/gpu/drm/msm/msm_ringbuffer.c

···
 	ring->memptrs_iova = memptrs_iova;
 
 	INIT_LIST_HEAD(&ring->submits);
+	spin_lock_init(&ring->lock);
 
 	snprintf(name, sizeof(name), "gpu-ring-%d", ring->id);
 

drivers/gpu/drm/msm/msm_ringbuffer.h

···
 	struct msm_rbmemptrs *memptrs;
 	uint64_t memptrs_iova;
 	struct msm_fence_context *fctx;
+	spinlock_t lock;
 };
 
 struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,