drm/i915: Fixup hpd irq register setup ordering

For GMCH platforms we set up the hpd irq registers in the irq
postinstall hook. But since we only enable the irq sources we actually
need in PORT_HOTPLUG_EN/STATUS, taking dev_priv->hotplug_supported_mask
into account, no hpd interrupt sources is enabled since

commit 52d7ecedac3f96fb562cb482c139015372728638
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sat Dec 1 21:03:22 2012 +0100

    drm/i915: reorder setup sequence to have irqs for output setup

Wrongly set-up interrupts also lead to broken hw-based load-detection
on at least GM45, resulting in ghost VGA/TV-out outputs.

To fix this, delay the hotplug register setup until after all outputs
are set up, by moving it into a new dev_priv->display.hpd_irq_callback.
We might also move the PCH_SPLIT platforms to such a setup eventually.

Another funny part is that we need to delay the fbdev initial config
probing until after the hpd regs are setup, for otherwise it'll detect
ghost outputs. But we can only enable the hpd interrupt handling
itself (and the output polling) _after_ that initial scan, due to
massive locking brain-damage in the fbdev setup code. Add a big
comment to explain this cute little dragon lair.

v2: Encapsulate all the fbdev handling by wrapping the move call into
intel_fbdev_initial_config in intel_fb.c. Requested by Chris Wilson.

v3: Applied bikeshed from Jesse Barnes.

v4: Imre Deak noticed that we also need to call intel_hpd_init after
the drm_irqinstall calls in the gpu reset and resume paths - otherwise
hotplug will be broken. Also improve the comment a bit about why
hpd_init needs to be called before we set up the initial fbdev config.

Bugzilla: Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=54943
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org> (v3)
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 93630669c6dc..0c2ab40ab2ed 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1319,6 +1319,21 @@ static int i915_load_modeset_init(struct drm_device *dev)
 		goto cleanup_gem;
 
 	/* Only enable hotplug handling once the fbdev is fully set up. */
+	intel_hpd_init(dev);
+
+	/*
+	 * Some ports require correctly set-up hpd registers for detection to
+	 * work properly (leading to ghost connected connector status), e.g. VGA
+	 * on gm45.  Hence we can only set up the initial fbdev config after hpd
+	 * irqs are fully enabled. Now we should scan for the initial config
+	 * only once hotplug handling is enabled, but due to screwed-up locking
+	 * around kms/fbdev init we can't protect the fdbev initial config
+	 * scanning against hotplug events. Hence do this first and ignore the
+	 * tiny window where we will loose hotplug notifactions.
+	 */
+	intel_fbdev_initial_config(dev);
+
+	/* Only enable hotplug handling once the fbdev is fully set up. */
 	dev_priv->enable_hotplug_processing = true;
 
 	drm_kms_helper_poll_init(dev);