linux-kernel - Re: [PATCH v8 4/4] drm/vc4: Allocate binner bo when starting to use the V3D

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Date:   Thu, 09 May 2019 11:39:17 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Eben Upton <eben@...pberrypi.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Subject: Re: [PATCH v8 4/4] drm/vc4: Allocate binner bo when starting to use the V3D

Paul Kocialkowski <paul.kocialkowski@...tlin.com> writes:

> The binner BO is not required until the V3D is in use, so avoid
> allocating it at probe and do it on the first non-dumb BO allocation.
>
> Keep track of which clients are using the V3D and liberate the buffer
> when there is none left, using a kref. Protect the logic with a
> mutex to avoid race conditions.
>
> The binner BO is created at the time of the first render ioctl and is
> destroyed when there is no client and no exec job using it left.
>
> The Out-Of-Memory (OOM) interrupt also gets some tweaking, to avoid
> enabling it before having allocated a binner bo.
>
> We also want to keep the BO alive during runtime suspend/resume to avoid
> failing to allocate it at resume. This happens when the CMA pool is
> full at that point and results in a hard crash.
>
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>

> @@ -313,6 +321,49 @@ static int bin_bo_alloc(struct vc4_dev *vc4)
>  	return ret;
>  }
>  
> +int vc4_v3d_bin_bo_get(struct vc4_dev *vc4, bool *used)
> +{
> +	int ret = 0;
> +
> +	mutex_lock(&vc4->bin_bo_lock);
> +
> +	if (used && *used)
> +		goto complete;



> +
> +	if (used)
> +		*used = true;
> +
> +	if (vc4->bin_bo) {
> +		kref_get(&vc4->bin_bo_kref);
> +		goto complete;
> +	}
> +
> +	ret = bin_bo_alloc(vc4);

I think this block wants to be:

if (vc4->bin_bo)
	kref_get(&vc4->bin_bo_kref);
else
	ret = bin_bo_alloc(vc4);

if (ret == 0 && used)
	*used = true;

(so we don't flag used if bin_bo_alloc fails)

If you agree, then the series is:

Reviewed-by: Eric Anholt <eric@...olt.net>

> +
> +complete:
> +	mutex_unlock(&vc4->bin_bo_lock);
> +
> +	return ret;
> +}


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