[PATCH 5/9] drm/i915: Enable i915 perf stream for Haswell OA unit

[Chris Wilson]

On Wed, Apr 20, 2016 at 03:23:10PM +0100, Robert Bragg wrote:
> +static void gen7_init_oa_buffer(struct drm_i915_private *dev_priv)
> +{
> +	/* Pre-DevBDW: OABUFFER must be set with counters off,
> +	 * before OASTATUS1, but after OASTATUS2
> +	 */
> +	I915_WRITE(GEN7_OASTATUS2, dev_priv->perf.oa.oa_buffer.gtt_offset |
> +		   OA_MEM_SELECT_GGTT); /* head */
> +	I915_WRITE(GEN7_OABUFFER, dev_priv->perf.oa.oa_buffer.gtt_offset);
> +	I915_WRITE(GEN7_OASTATUS1, dev_priv->perf.oa.oa_buffer.gtt_offset |
> +		   OABUFFER_SIZE_16M); /* tail */
> +
> +	/* On Haswell we have to track which OASTATUS1 flags we've
> +	 * already seen since they can't be cleared while periodic
> +	 * sampling is enabled.
> +	 */
> +	dev_priv->perf.oa.gen7_latched_oastatus1 = 0;
> +
> +	/* We have a sanity check in gen7_append_oa_reports() that
> +	 * looks at the report-id field to make sure it's non-zero
> +	 * which relies on the assumption that new reports are
> +	 * being written to zeroed memory...
> +	 */
> +	memset(dev_priv->perf.oa.oa_buffer.addr, 0, SZ_16M);

You allocated zeroed memory.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre