Commit 8102e126 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/tv: Use polling rather than interrupt-based hotplug 



The documentation recommends that we should use a polling method for TV
detection as this is more power efficient than the interrupt based
mechanism (as the encoder can be completely switched off). A secondary
effect is that leaving the hotplug enabled seems to be causing pipe
underruns as reported by Hugh Dickins on his Crestline.

Tested-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
[This is a candidate for stable, but needs minor porting to 2.6.37]
parent 1aad7ac0

drivers/gpu/drm/i915/intel_tv.c

+30 −13
Original line number Diff line number Diff line
@@ -1234,7 +1234,8 @@ static const struct drm_display_mode reported_modes[] = { 
 * \return false if TV is disconnected.

 */

static int

intel_tv_detect_type (struct intel_tv *intel_tv)

intel_tv_detect_type (struct intel_tv *intel_tv,

		      struct drm_connector *connector)

{

	struct drm_encoder *encoder = &intel_tv->base.base;

	struct drm_device *dev = encoder->dev;
@@ -1245,11 +1246,13 @@ intel_tv_detect_type (struct intel_tv *intel_tv) 
	int type;



	/* Disable TV interrupts around load detect or we'll recurse */

	if (connector->polled & DRM_CONNECTOR_POLL_HPD) {

		spin_lock_irqsave(&dev_priv->irq_lock, irqflags);

		i915_disable_pipestat(dev_priv, 0,

				      PIPE_HOTPLUG_INTERRUPT_ENABLE |

				      PIPE_HOTPLUG_TV_INTERRUPT_ENABLE);

		spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);

	}



	save_tv_dac = tv_dac = I915_READ(TV_DAC);

	save_tv_ctl = tv_ctl = I915_READ(TV_CTL);
@@ -1302,11 +1305,13 @@ intel_tv_detect_type (struct intel_tv *intel_tv) 
	I915_WRITE(TV_CTL, save_tv_ctl);



	/* Restore interrupt config */

	if (connector->polled & DRM_CONNECTOR_POLL_HPD) {

		spin_lock_irqsave(&dev_priv->irq_lock, irqflags);

		i915_enable_pipestat(dev_priv, 0,

				     PIPE_HOTPLUG_INTERRUPT_ENABLE |

				     PIPE_HOTPLUG_TV_INTERRUPT_ENABLE);

		spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);

	}



	return type;

}
@@ -1356,7 +1361,7 @@ intel_tv_detect(struct drm_connector *connector, bool force) 
	drm_mode_set_crtcinfo(&mode, CRTC_INTERLACE_HALVE_V);



	if (intel_tv->base.base.crtc && intel_tv->base.base.crtc->enabled) {

		type = intel_tv_detect_type(intel_tv);

		type = intel_tv_detect_type(intel_tv, connector);

	} else if (force) {

		struct drm_crtc *crtc;

		int dpms_mode;
@@ -1364,7 +1369,7 @@ intel_tv_detect(struct drm_connector *connector, bool force) 
		crtc = intel_get_load_detect_pipe(&intel_tv->base, connector,

						  &mode, &dpms_mode);

		if (crtc) {

			type = intel_tv_detect_type(intel_tv);

			type = intel_tv_detect_type(intel_tv, connector);

			intel_release_load_detect_pipe(&intel_tv->base, connector,

						       dpms_mode);

		} else
@@ -1658,6 +1663,18 @@ intel_tv_init(struct drm_device *dev) 
	intel_encoder = &intel_tv->base;

	connector = &intel_connector->base;



	/* The documentation, for the older chipsets at least, recommend

	 * using a polling method rather than hotplug detection for TVs.

	 * This is because in order to perform the hotplug detection, the PLLs

	 * for the TV must be kept alive increasing power drain and starving

	 * bandwidth from other encoders. Notably for instance, it causes

	 * pipe underruns on Crestline when this encoder is supposedly idle.

	 *

	 * More recent chipsets favour HDMI rather than integrated S-Video.

	 */

	connector->polled =

		DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;



	drm_connector_init(dev, connector, &intel_tv_connector_funcs,

			   DRM_MODE_CONNECTOR_SVIDEO);

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