From mboxrd@z Thu Jan  1 00:00:00 1970
From: Damien Lespiau <damien.lespiau@intel.com>
Subject: Re: [PATCH] drm/i915: debugfs: Add support for probing
	DP sink CRC.
Date: Fri, 24 Jan 2014 12:40:21 +0000
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	<1390565132-25100-1-git-send-email-rodrigo.vivi@gmail.com>
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To: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Cc: Jani Nikula <jani.nikula@intel.com>, Daniel Vetter <daniel.vetter@ffwll.ch>, intel-gfx@lists.freedesktop.org
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On Fri, Jan 24, 2014 at 10:05:32AM -0200, Rodrigo Vivi wrote:
> +int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
> +{
> +	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> +	struct drm_device *dev = intel_dig_port->base.base.dev;
> +	struct intel_crtc *intel_crtc =
> +		to_intel_crtc(intel_dig_port->base.base.crtc);
> +	u8 buf[1];
> +
> +	if (!intel_dp_aux_native_read(intel_dp, DP_TEST_SINK_MISC, buf, 1))
> +		return -EAGAIN;
> +
> +	if (!(buf[0] & DP_TEST_CRC_SUPPORTED))
> +		return -ENOTTY;
> +
> +	if (!intel_dp_aux_native_write_1(intel_dp, DP_TEST_SINK,
> +					 DP_TEST_SINK_START))
> +		return -EAGAIN;
> +
> +	/* Wait 2 vblanks to be sure we will have the correct CRC value */
> +	intel_wait_for_vblank(dev, intel_crtc->pipe);
> +	intel_wait_for_vblank(dev, intel_crtc->pipe);
> +
> +	if (!intel_dp_aux_native_read_retry(intel_dp, DP_TEST_CRC_R_CR, crc, 6))
> +		return -EAGAIN;

There's still one retry hidden here.

-- 
Damien