[PATCH] drm/i915: Ensure proper HDA suspend/resume ordering with a device link

[Imre Deak <imre.deak@intel.com>]

In order to ensure that our system suspend and resume callbacks are
called in the correct order wrt. those of the HDA driver add a device
link to the HDA driver during audio component binding time. With i915 as
the supplier and HDA as the consumer the PM framework will guarantee
the HDA->i915 suspend (and shutdown) and i915->HDA resume order.

Atm, the lack of this ordering is not a problem, since all the i915
suspend/resume steps that need to be ordered wrt. the HDA driver's
suspend/resume steps are separated out to the i915
suspend_late/resume_early hooks. That will change in a follow-up
patchset where we'll need this ordering guarantee for steps that are in
the i915 suspend/resume hooks (and which can't be moved to
suspend_late/resume_early for other reasons). So this patch is a
preparation for that follow-up patchset.

The change also allows us to move towards removing the i915
suspend_late/resume_early hooks alltogether.

Since we only need to ensure the ordering during suspend/resume and not
during driver probing create the link with DL_FLAG_STATELESS. Since the
probe time ordering has to be optional we use the component framework
for that.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/intel_audio.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
index 769f3f586661..391b88701610 100644
--- a/drivers/gpu/drm/i915/intel_audio.c
+++ b/drivers/gpu/drm/i915/intel_audio.c
@@ -921,6 +921,8 @@ static int i915_audio_component_bind(struct device *i915_kdev,
 	dev_priv->audio_component = acomp;
 	drm_modeset_unlock_all(&dev_priv->drm);
 
+	WARN_ON(!device_link_add(hda_kdev, i915_kdev, DL_FLAG_STATELESS));
+
 	return 0;
 }
 
@@ -930,6 +932,8 @@ static void i915_audio_component_unbind(struct device *i915_kdev,
 	struct i915_audio_component *acomp = data;
 	struct drm_i915_private *dev_priv = kdev_to_i915(i915_kdev);
 
+	device_link_remove(hda_kdev, i915_kdev);
+
 	drm_modeset_lock_all(&dev_priv->drm);
 	acomp->base.ops = NULL;
 	acomp->base.dev = NULL;
-- 
2.13.2

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