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Date:   Mon, 5 Oct 2020 08:22:26 -0600
From:   Jordan Crouse <jcrouse@codeaurora.org>
To:     Rob Clark <robdclark@gmail.com>
Cc:     dri-devel@lists.freedesktop.org,
        Rob Clark <robdclark@chromium.org>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Eric Anholt <eric@anholt.net>,
        Emil Velikov <emil.velikov@collabora.com>,
        AngeloGioacchino Del Regno <kholk11@gmail.com>,
        Ben Dooks <ben.dooks@codethink.co.uk>,
        Jonathan Marek <jonathan@marek.ca>,
        Akhil P Oommen <akhilpo@codeaurora.org>,
        Sharat Masetty <smasetty@codeaurora.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@vger.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/14] drm/msm: Document and rename preempt_lock
Message-ID: <20201005142226.GD4204@jcrouse1-lnx.qualcomm.com>
Mail-Followup-To: Rob Clark <robdclark@gmail.com>,
        dri-devel@lists.freedesktop.org, Rob Clark <robdclark@chromium.org>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Eric Anholt <eric@anholt.net>,
        Emil Velikov <emil.velikov@collabora.com>,
        AngeloGioacchino Del Regno <kholk11@gmail.com>,
        Ben Dooks <ben.dooks@codethink.co.uk>,
        Jonathan Marek <jonathan@marek.ca>,
        Akhil P Oommen <akhilpo@codeaurora.org>,
        Sharat Masetty <smasetty@codeaurora.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" <linux-arm-msm@vger.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" <freedreno@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>
References: <20201004192152.3298573-1-robdclark@gmail.com>
 <20201004192152.3298573-6-robdclark@gmail.com>
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On Sun, Oct 04, 2020 at 12:21:37PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> Before adding another lock, give ring->lock a more descriptive name.

Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>

> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  drivers/gpu/drm/msm/adreno/a5xx_gpu.c     |  4 ++--
>  drivers/gpu/drm/msm/adreno/a5xx_preempt.c | 12 ++++++------
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c     |  4 ++--
>  drivers/gpu/drm/msm/msm_ringbuffer.c      |  2 +-
>  drivers/gpu/drm/msm/msm_ringbuffer.h      |  7 ++++++-
>  5 files changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> index c941c8138f25..543437a2186e 100644
> --- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> @@ -36,7 +36,7 @@ void a5xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>  		OUT_RING(ring, upper_32_bits(shadowptr(a5xx_gpu, ring)));
>  	}
>  
> -	spin_lock_irqsave(&ring->lock, flags);
> +	spin_lock_irqsave(&ring->preempt_lock, flags);
>  
>  	/* Copy the shadow to the actual register */
>  	ring->cur = ring->next;
> @@ -44,7 +44,7 @@ void a5xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>  	/* Make sure to wrap wptr if we need to */
>  	wptr = get_wptr(ring);
>  
> -	spin_unlock_irqrestore(&ring->lock, flags);
> +	spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  	/* Make sure everything is posted before making a decision */
>  	mb();
> diff --git a/drivers/gpu/drm/msm/adreno/a5xx_preempt.c b/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
> index 7e04509c4e1f..183de1139eeb 100644
> --- a/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
> +++ b/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
> @@ -45,9 +45,9 @@ static inline void update_wptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
>  	if (!ring)
>  		return;
>  
> -	spin_lock_irqsave(&ring->lock, flags);
> +	spin_lock_irqsave(&ring->preempt_lock, flags);
>  	wptr = get_wptr(ring);
> -	spin_unlock_irqrestore(&ring->lock, flags);
> +	spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  	gpu_write(gpu, REG_A5XX_CP_RB_WPTR, wptr);
>  }
> @@ -62,9 +62,9 @@ static struct msm_ringbuffer *get_next_ring(struct msm_gpu *gpu)
>  		bool empty;
>  		struct msm_ringbuffer *ring = gpu->rb[i];
>  
> -		spin_lock_irqsave(&ring->lock, flags);
> +		spin_lock_irqsave(&ring->preempt_lock, flags);
>  		empty = (get_wptr(ring) == ring->memptrs->rptr);
> -		spin_unlock_irqrestore(&ring->lock, flags);
> +		spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  		if (!empty)
>  			return ring;
> @@ -132,9 +132,9 @@ void a5xx_preempt_trigger(struct msm_gpu *gpu)
>  	}
>  
>  	/* Make sure the wptr doesn't update while we're in motion */
> -	spin_lock_irqsave(&ring->lock, flags);
> +	spin_lock_irqsave(&ring->preempt_lock, flags);
>  	a5xx_gpu->preempt[ring->id]->wptr = get_wptr(ring);
> -	spin_unlock_irqrestore(&ring->lock, flags);
> +	spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  	/* Set the address of the incoming preemption record */
>  	gpu_write64(gpu, REG_A5XX_CP_CONTEXT_SWITCH_RESTORE_ADDR_LO,
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 8915882e4444..fc85f008d69d 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -65,7 +65,7 @@ static void a6xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
>  		OUT_RING(ring, upper_32_bits(shadowptr(a6xx_gpu, ring)));
>  	}
>  
> -	spin_lock_irqsave(&ring->lock, flags);
> +	spin_lock_irqsave(&ring->preempt_lock, flags);
>  
>  	/* Copy the shadow to the actual register */
>  	ring->cur = ring->next;
> @@ -73,7 +73,7 @@ static void a6xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
>  	/* Make sure to wrap wptr if we need to */
>  	wptr = get_wptr(ring);
>  
> -	spin_unlock_irqrestore(&ring->lock, flags);
> +	spin_unlock_irqrestore(&ring->preempt_lock, flags);
>  
>  	/* Make sure everything is posted before making a decision */
>  	mb();
> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> index 935bf9b1d941..1b6958e908dc 100644
> --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
> @@ -46,7 +46,7 @@ struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
>  	ring->memptrs_iova = memptrs_iova;
>  
>  	INIT_LIST_HEAD(&ring->submits);
> -	spin_lock_init(&ring->lock);
> +	spin_lock_init(&ring->preempt_lock);
>  
>  	snprintf(name, sizeof(name), "gpu-ring-%d", ring->id);
>  
> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.h b/drivers/gpu/drm/msm/msm_ringbuffer.h
> index 0987d6bf848c..4956d1bc5d0e 100644
> --- a/drivers/gpu/drm/msm/msm_ringbuffer.h
> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.h
> @@ -46,7 +46,12 @@ struct msm_ringbuffer {
>  	struct msm_rbmemptrs *memptrs;
>  	uint64_t memptrs_iova;
>  	struct msm_fence_context *fctx;
> -	spinlock_t lock;
> +
> +	/*
> +	 * preempt_lock protects preemption and serializes wptr updates against
> +	 * preemption.  Can be aquired from irq context.
> +	 */
> +	spinlock_t preempt_lock;
>  };
>  
>  struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
> -- 
> 2.26.2
> 

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