Re: Fw: [Intel-gfx] [PATCH] intel: add a timed wait function

From: Eric Anholt <eric@anholt.net>
To: Ben Widawsky <ben@bwidawsk.net>,
	dri-devel@lists.freedesktop.org, mesa-dev@lists.freedesktop.org
Subject: Re: Fw: [Intel-gfx] [PATCH] intel: add a timed wait function
Date: Wed, 30 May 2012 10:41:20 -0700	[thread overview]
Message-ID: <87vcjdk1mn.fsf@eliezer.anholt.net> (raw)
In-Reply-To: <20120527131654.4501e518@bwidawsk.net>

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On Sun, 27 May 2012 13:16:54 -0700, Ben Widawsky <ben@bwidawsk.net> wrote:
> diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
> index b776d2f..695a449 100644
> --- a/intel/intel_bufmgr_gem.c
> +++ b/intel/intel_bufmgr_gem.c
> @@ -1478,6 +1478,32 @@ drm_intel_gem_bo_wait_rendering(drm_intel_bo *bo)
>  	drm_intel_gem_bo_start_gtt_access(bo, 1);
>  }
>  
> +int drm_intel_gem_bo_wait(drm_intel_bo *bo, uint64_t *timeout_ns)
> +{
> +	drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)
> bo->bufmgr;
> +	drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *) bo;
> +	struct drm_i915_gem_wait wait;
> +	int ret;
> +
> +	if (!timeout_ns)
> +		return -EINVAL;

At least for the GL case, timeout of 0 ns wants to turn into
GL_TIMEOUT_EXPIRED or GL_ALREADY_SIGNALED.  -EINVAL doesn't sound like
translating into either of those -- are you thinking that GL will
special case 0 ns to not call this function?

> +
> +	wait.bo_handle = bo_gem->gem_handle;
> +	wait.timeout_ns = *timeout_ns;
> +	wait.flags = 0;
> +	ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_I915_GEM_WAIT, &wait);
> +	if (ret)
> +		return ret;
> +
> +	if (wait.timeout_ns == 0) {
> +		DBG("Wait timed out on buffer %d\n",
> bo_gem->gem_handle);
> +		*timeout_ns = 0;
> +	} else
> +		*timeout_ns = wait.timeout_ns;
> +
> +	return ret;
> +}

Do we see any consumers wanting the unslept time?  GL doesn't care, and
not passing a pointer would be more convenient for the caller.

I guess GL_ALREADY_SIGNALED handling will be done using a check for
bo_busy() before calling this.

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