drm/i915/gen9: Fix runtime PM refcounting in case DMC firmware isn't loaded

While we disable runtime PM and with that display power well support if
the DMC firmware isn't loaded, we still want to disable power wells
during system suspend and driver unload. So drop/reacquire the
corresponding power refcount during suspend/resume and driver unloading.
This also means we have to check if DMC is not loaded and skip enabling
DC states in the power well code.

v2:
- Reuse intel_csr_ucode_suspend() in intel_csr_ucode_fini() instead of
  opencoding the former. (Chris)
- Add docbook comment to the public resume and suspend functions.

CC: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460980101-14713-1-git-send-email-imre.deak@intel.com

1 files changed, 42 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index d57b00ed5e5e..a34c23eceba0 100644
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -467,10 +467,50 @@ void intel_csr_ucode_init(struct drm_i915_private *dev_priv)
 }
 
 /**
+ * intel_csr_ucode_suspend() - prepare CSR firmware before system suspend
+ * @dev_priv: i915 drm device
+ *
+ * Prepare the DMC firmware before entering system suspend. This includes
+ * flushing pending work items and releasing any resources acquired during
+ * init.
+ */
+void intel_csr_ucode_suspend(struct drm_i915_private *dev_priv)
+{
+	if (!HAS_CSR(dev_priv))
+		return;
+
+	flush_work(&dev_priv->csr.work);
+
+	/* Drop the reference held in case DMC isn't loaded. */
+	if (!dev_priv->csr.dmc_payload)
+		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
+}
+
+/**
+ * intel_csr_ucode_resume() - init CSR firmware during system resume
+ * @dev_priv: i915 drm device
+ *
+ * Reinitialize the DMC firmware during system resume, reacquiring any
+ * resources released in intel_csr_ucode_suspend().
+ */
+void intel_csr_ucode_resume(struct drm_i915_private *dev_priv)
+{
+	if (!HAS_CSR(dev_priv))
+		return;
+
+	/*
+	 * Reacquire the reference to keep RPM disabled in case DMC isn't
+	 * loaded.
+	 */
+	if (!dev_priv->csr.dmc_payload)
+		intel_display_power_get(dev_priv, POWER_DOMAIN_INIT);
+}
+
+/**
  * intel_csr_ucode_fini() - unload the CSR firmware.
  * @dev_priv: i915 drm device.
  *
- * Firmmware unloading includes freeing the internal momory and reset the
+ * Firmmware unloading includes freeing the internal memory and reset the
  * firmware loading status.
  */
 void intel_csr_ucode_fini(struct drm_i915_private *dev_priv)
@@ -478,7 +518,7 @@ void intel_csr_ucode_fini(struct drm_i915_private *dev_priv)
 	if (!HAS_CSR(dev_priv))
 		return;
 
-	flush_work(&dev_priv->csr.work);
+	intel_csr_ucode_suspend(dev_priv);
 
 	kfree(dev_priv->csr.dmc_payload);
 }