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Commit 6ec3d0c0 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/crt: Use a DDC probe on 0xA0 before load-detect 



The BIOS writer's guide suggests that a VGA connection will ACK a write
to address 0xA0 and that this should be used before doing legacy
load-detection. Considering the extreme cost of load-detection,
performing an extra DDC seems a risk worth taking.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
parent a5cad620

drivers/gpu/drm/i915/intel_crt.c

+35 −4
Original line number Diff line number Diff line
@@ -261,6 +261,21 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector) 
	return ret;

}



static bool intel_crt_ddc_probe(struct drm_i915_private *dev_priv, int ddc_bus)

{

	u8 buf;

	struct i2c_msg msgs[] = {

		{

			.addr = 0xA0,

			.flags = 0,

			.len = 1,

			.buf = &buf,

		},

	};

	/* DDC monitor detect: Does it ACK a write to 0xA0? */

	return i2c_transfer(&dev_priv->gmbus[ddc_bus].adapter, msgs, 1) == 1;

}



static bool intel_crt_detect_ddc(struct drm_encoder *encoder)

{

	struct intel_encoder *intel_encoder = to_intel_encoder(encoder);
@@ -270,7 +285,17 @@ static bool intel_crt_detect_ddc(struct drm_encoder *encoder) 
	if (intel_encoder->type != INTEL_OUTPUT_ANALOG)

		return false;



	return intel_ddc_probe(intel_encoder, dev_priv->crt_ddc_pin);

	if (intel_crt_ddc_probe(dev_priv, dev_priv->crt_ddc_pin)) {

		DRM_DEBUG_KMS("CRT detected via DDC:0xa0\n");

		return true;

	}



	if (intel_ddc_probe(intel_encoder, dev_priv->crt_ddc_pin)) {

		DRM_DEBUG_KMS("CRT detected via DDC:0x50 [EDID]\n");

		return true;

	}



	return false;

}



static enum drm_connector_status
@@ -296,6 +321,8 @@ intel_crt_load_detect(struct drm_crtc *crtc, struct intel_encoder *intel_encoder 
	uint8_t	st00;

	enum drm_connector_status status;



	DRM_DEBUG_KMS("starting load-detect on CRT\n");



	if (pipe == 0) {

		bclrpat_reg = BCLRPAT_A;

		vtotal_reg = VTOTAL_A;
@@ -412,9 +439,10 @@ intel_crt_detect(struct drm_connector *connector, bool force) 
	enum drm_connector_status status;



	if (I915_HAS_HOTPLUG(dev)) {

		if (intel_crt_detect_hotplug(connector))

		if (intel_crt_detect_hotplug(connector)) {

			DRM_DEBUG_KMS("CRT detected via hotplug\n");

			return connector_status_connected;

		else

		} else

			return connector_status_disconnected;

	}
@@ -431,6 +459,9 @@ intel_crt_detect(struct drm_connector *connector, bool force) 
		crtc = intel_get_load_detect_pipe(encoder, connector,

						  NULL, &dpms_mode);

		if (crtc) {

			if (intel_crt_detect_ddc(&encoder->base))

				status = connector_status_connected;

			else

				status = intel_crt_load_detect(crtc, encoder);

			intel_release_load_detect_pipe(encoder,

						       connector, dpms_mode);