Re: [PATCH 3/3] drm/amdgpu: busywait KIQ register accessing v2

["Christian König" <christian.koenig-5C7GfCeVMHo@public.gmane.org>]

Am 17.10.2017 um 08:37 schrieb Pixel Ding:
> From: pding <Pixel.Ding@amd.com>
>
> Register accessing is performed when IRQ is disabled. Never sleep in
> this function.
>
> Known issue: dead sleep in many use cases of index/data registers.
>
> v2: wrap polling fence functions. don't trigger IRQ for polling in
> case of wrongly fence signal.
>
> Signed-off-by: pding <Pixel.Ding@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu.h               |  2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v8.c |  4 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v9.c |  4 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c        |  8 +---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c         | 53 +++++++++++++++++++++++
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c           |  2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h          |  4 ++
>   drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c          | 30 ++++++-------
>   8 files changed, 78 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index ca212ef..cc06e62 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -885,7 +885,7 @@ struct amdgpu_mec {
>   struct amdgpu_kiq {
>   	u64			eop_gpu_addr;
>   	struct amdgpu_bo	*eop_obj;
> -	struct mutex		ring_mutex;
> +	spinlock_t              ring_lock;
>   	struct amdgpu_ring	ring;
>   	struct amdgpu_irq_src	irq;
>   };
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v8.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v8.c
> index 9d9965d..6d83573 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v8.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v8.c
> @@ -788,7 +788,7 @@ static int invalidate_tlbs_with_kiq(struct amdgpu_device *adev, uint16_t pasid)
>   	struct dma_fence *f;
>   	struct amdgpu_ring *ring = &adev->gfx.kiq.ring;
>   
> -	mutex_lock(&adev->gfx.kiq.ring_mutex);
> +	spin_lock(&adev->gfx.kiq.ring_lock);
>   	amdgpu_ring_alloc(ring, 12); /* fence + invalidate_tlbs package*/
>   	amdgpu_ring_write(ring, PACKET3(PACKET3_INVALIDATE_TLBS, 0));
>   	amdgpu_ring_write(ring,
> @@ -796,7 +796,7 @@ static int invalidate_tlbs_with_kiq(struct amdgpu_device *adev, uint16_t pasid)
>   			PACKET3_INVALIDATE_TLBS_PASID(pasid));
>   	amdgpu_fence_emit(ring, &f);
>   	amdgpu_ring_commit(ring);
> -	mutex_unlock(&adev->gfx.kiq.ring_mutex);
> +	spin_unlock(&adev->gfx.kiq.ring_lock);
>   
>   	r = dma_fence_wait(f, false);
>   	if (r)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v9.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v9.c
> index edbae19..c92217f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v9.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gfx_v9.c
> @@ -973,7 +973,7 @@ static int invalidate_tlbs_with_kiq(struct amdgpu_device *adev, uint16_t pasid)
>   	struct dma_fence *f;
>   	struct amdgpu_ring *ring = &adev->gfx.kiq.ring;
>   
> -	mutex_lock(&adev->gfx.kiq.ring_mutex);
> +	spin_lock(&adev->gfx.kiq.ring_lock);
>   	amdgpu_ring_alloc(ring, 12); /* fence + invalidate_tlbs package*/
>   	amdgpu_ring_write(ring, PACKET3(PACKET3_INVALIDATE_TLBS, 0));
>   	amdgpu_ring_write(ring,
> @@ -983,7 +983,7 @@ static int invalidate_tlbs_with_kiq(struct amdgpu_device *adev, uint16_t pasid)
>   			PACKET3_INVALIDATE_TLBS_FLUSH_TYPE(2));
>   	amdgpu_fence_emit(ring, &f);
>   	amdgpu_ring_commit(ring);
> -	mutex_unlock(&adev->gfx.kiq.ring_mutex);
> +	spin_unlock(&adev->gfx.kiq.ring_lock);
>   
>   	r = dma_fence_wait(f, false);
>   	if (r)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index ab8f0d6..1197274 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -109,10 +109,8 @@ uint32_t amdgpu_mm_rreg(struct amdgpu_device *adev, uint32_t reg,
>   {
>   	uint32_t ret;
>   
> -	if (!(acc_flags & AMDGPU_REGS_NO_KIQ) && amdgpu_sriov_runtime(adev)) {
> -		BUG_ON(in_interrupt());
> +	if (!(acc_flags & AMDGPU_REGS_NO_KIQ) && amdgpu_sriov_runtime(adev))
>   		return amdgpu_virt_kiq_rreg(adev, reg);
> -	}
>   
>   	if ((reg * 4) < adev->rmmio_size && !(acc_flags & AMDGPU_REGS_IDX))
>   		ret = readl(((void __iomem *)adev->rmmio) + (reg * 4));
> @@ -137,10 +135,8 @@ void amdgpu_mm_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v,
>   		adev->last_mm_index = v;
>   	}
>   
> -	if (!(acc_flags & AMDGPU_REGS_NO_KIQ) && amdgpu_sriov_runtime(adev)) {
> -		BUG_ON(in_interrupt());
> +	if (!(acc_flags & AMDGPU_REGS_NO_KIQ) && amdgpu_sriov_runtime(adev))
>   		return amdgpu_virt_kiq_wreg(adev, reg, v);
> -	}
>   
>   	if ((reg * 4) < adev->rmmio_size && !(acc_flags & AMDGPU_REGS_IDX))
>   		writel(v, ((void __iomem *)adev->rmmio) + (reg * 4));
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> index 688740e..68a5e90 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> @@ -169,6 +169,32 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f)
>   }
>   
>   /**
> + * amdgpu_fence_emit_polling - emit a fence on the requeste ring
> + *
> + * @ring: ring the fence is associated with
> + * @s: resulting sequence number
> + *
> + * Emits a fence command on the requested ring (all asics).
> + * Used For polling fence.
> + * Returns 0 on success, -ENOMEM on failure.
> + */
> +int amdgpu_fence_emit_polling(struct amdgpu_ring *ring, uint32_t *s)
> +{
> +	uint32_t seq;
> +
> +	if (!s)
> +		return -EINVAL;
> +
> +	seq = ++ring->fence_drv.sync_seq;
> +	amdgpu_ring_emit_fence(ring, ring->fence_drv.gpu_addr,
> +			       seq, AMDGPU_FENCE_FLAG_INT);
> +
> +	*s = seq;
> +
> +	return 0;
> +}
> +
> +/**
>    * amdgpu_fence_schedule_fallback - schedule fallback check
>    *
>    * @ring: pointer to struct amdgpu_ring
> @@ -281,6 +307,33 @@ int amdgpu_fence_wait_empty(struct amdgpu_ring *ring)
>   	return r;
>   }
>   

Please add some documentation here that timeout is in usec.

> +signed long amdgpu_fence_wait_polling(struct amdgpu_ring *ring,
> +				      uint32_t wait_seq,
> +				      signed long timeout)
> +{
> +	uint32_t seq, last_seq;
> +	struct amdgpu_fence_driver *drv = &ring->fence_drv;
> +
> +	last_seq = atomic_read(&ring->fence_drv.last_seq);
> +
> +	do {
> +		seq = amdgpu_fence_read(ring);
> +
> +		if (unlikely(seq == last_seq))
> +			break;

That doesn't look correct to me, it will abort the busy wait as soon as 
we see the last value we have seen.

> +		if (seq >= wait_seq && wait_seq >= last_seq)
> +			break;
> +		if (seq <= last_seq &&
> +		    (wait_seq <= seq || wait_seq >= last_seq))
> +			break;

Why not just "(int32_t)(wait_seq - seq) > 0" ? IIRC that should be 
sufficient for a wrap around test.

Regards,
Christian.

> +		udelay(5);
> +		timeout -= 5;
> +	} while (timeout > 0);
> +
> +	atomic_cmpxchg(&drv->last_seq, last_seq, wait_seq);
> +
> +	return timeout;
> +}
>   /**
>    * amdgpu_fence_count_emitted - get the count of emitted fences
>    *
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> index 4f6c68f..e5a9077 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> @@ -185,7 +185,7 @@ int amdgpu_gfx_kiq_init_ring(struct amdgpu_device *adev,
>   	struct amdgpu_kiq *kiq = &adev->gfx.kiq;
>   	int r = 0;
>   
> -	mutex_init(&kiq->ring_mutex);
> +	spin_lock_init(&kiq->ring_lock);
>   
>   	r = amdgpu_wb_get(adev, &adev->virt.reg_val_offs);
>   	if (r)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> index af8e544..9de89ea 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> @@ -89,8 +89,12 @@ int amdgpu_fence_driver_start_ring(struct amdgpu_ring *ring,
>   void amdgpu_fence_driver_suspend(struct amdgpu_device *adev);
>   void amdgpu_fence_driver_resume(struct amdgpu_device *adev);
>   int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **fence);
> +int amdgpu_fence_emit_polling(struct amdgpu_ring *ring, uint32_t *s);
>   void amdgpu_fence_process(struct amdgpu_ring *ring);
>   int amdgpu_fence_wait_empty(struct amdgpu_ring *ring);
> +signed long amdgpu_fence_wait_polling(struct amdgpu_ring *ring,
> +				      uint32_t wait_seq,
> +				      signed long timeout);
>   unsigned amdgpu_fence_count_emitted(struct amdgpu_ring *ring);
>   
>   /*
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
> index ab05121..177fe10 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
> @@ -22,7 +22,7 @@
>    */
>   
>   #include "amdgpu.h"
> -#define MAX_KIQ_REG_WAIT	100000
> +#define MAX_KIQ_REG_WAIT	100000000 /* in usecs */
>   
>   int amdgpu_allocate_static_csa(struct amdgpu_device *adev)
>   {
> @@ -114,27 +114,24 @@ void amdgpu_virt_init_setting(struct amdgpu_device *adev)
>   uint32_t amdgpu_virt_kiq_rreg(struct amdgpu_device *adev, uint32_t reg)
>   {
>   	signed long r;
> -	uint32_t val;
> -	struct dma_fence *f;
> +	uint32_t val, seq;
>   	struct amdgpu_kiq *kiq = &adev->gfx.kiq;
>   	struct amdgpu_ring *ring = &kiq->ring;
>   
>   	BUG_ON(!ring->funcs->emit_rreg);
>   
> -	mutex_lock(&kiq->ring_mutex);
> +	spin_lock(&kiq->ring_lock);
>   	amdgpu_ring_alloc(ring, 32);
>   	amdgpu_ring_emit_rreg(ring, reg);
> -	amdgpu_fence_emit(ring, &f);
> +	amdgpu_fence_emit_polling(ring, &seq);
>   	amdgpu_ring_commit(ring);
> -	mutex_unlock(&kiq->ring_mutex);
> +	spin_unlock(&kiq->ring_lock);
>   
> -	r = dma_fence_wait_timeout(f, false, msecs_to_jiffies(MAX_KIQ_REG_WAIT));
> -	dma_fence_put(f);
> +	r = amdgpu_fence_wait_polling(ring, seq, MAX_KIQ_REG_WAIT);
>   	if (r < 1) {
> -		DRM_ERROR("wait for kiq fence error: %ld.\n", r);
> +		DRM_ERROR("wait for kiq fence error: %ld\n", r);
>   		return ~0;
>   	}
> -
>   	val = adev->wb.wb[adev->virt.reg_val_offs];
>   
>   	return val;
> @@ -143,23 +140,22 @@ uint32_t amdgpu_virt_kiq_rreg(struct amdgpu_device *adev, uint32_t reg)
>   void amdgpu_virt_kiq_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v)
>   {
>   	signed long r;
> -	struct dma_fence *f;
> +	uint32_t seq;
>   	struct amdgpu_kiq *kiq = &adev->gfx.kiq;
>   	struct amdgpu_ring *ring = &kiq->ring;
>   
>   	BUG_ON(!ring->funcs->emit_wreg);
>   
> -	mutex_lock(&kiq->ring_mutex);
> +	spin_lock(&kiq->ring_lock);
>   	amdgpu_ring_alloc(ring, 32);
>   	amdgpu_ring_emit_wreg(ring, reg, v);
> -	amdgpu_fence_emit(ring, &f);
> +	amdgpu_fence_emit_polling(ring, &seq);
>   	amdgpu_ring_commit(ring);
> -	mutex_unlock(&kiq->ring_mutex);
> +	spin_unlock(&kiq->ring_lock);
>   
> -	r = dma_fence_wait_timeout(f, false, msecs_to_jiffies(MAX_KIQ_REG_WAIT));
> +	r = amdgpu_fence_wait_polling(ring, seq, MAX_KIQ_REG_WAIT);
>   	if (r < 1)
> -		DRM_ERROR("wait for kiq fence error: %ld.\n", r);
> -	dma_fence_put(f);
> +		DRM_ERROR("wait for kiq fence error: %ld\n", r);
>   }
>   
>   /**


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