drm/i915: send PCI_D3hot adapter opregion message on BDW RPM suspend

On BDW we're seeing a problem that after we runtime resume, the
outputs connected to DDI C are not detected: they don't appear in the
SDEISR register and GMBUS transactions don't work. They stop working
at the moment we call intel_opregion_notify_adapter() during runtime
suspend, but they don't go back to work when we call the same function
during runtime resume. They only work after we do a modeset and call
intel_opregion_notify_encoder(), but this point is already too late.

While debugging, I tried to pass PCI_D3hot which is the value that
matches the spec, and it seems to have solved the problem. I couldn't
find any explanation of why this solves the problem, but there's also
no documented explanation - besides our code and git log - of why
Haswell should use PCI_D1, so keep this for now in order to keep BDW
runtime PM working.

Also add a comment to point the fact that there's no spec documenting
all the weirdness involved here.

Cc: kristen.c.accardi@intel.com
Testcase: igt/pm_rpm/drm-resources-equal
Testcase: igt/pm_rpm/i2c
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 683be99117c64192b8a5c643b81e55cbdf62b991..d02398720237c9e9d85ecf604b8e93478d63b895 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1462,13 +1462,29 @@ static int intel_runtime_suspend(struct device *device)
        dev_priv->pm.suspended = true;
 
        /*
-        * current versions of firmware which depend on this opregion
-        * notification have repurposed the D1 definition to mean
-        * "runtime suspended" vs. what you would normally expect (D3)
-        * to distinguish it from notifications that might be sent
-        * via the suspend path.
+        * FIXME: We really should find a document that references the arguments
+        * used below!
         */
-       intel_opregion_notify_adapter(dev, PCI_D1);
+       if (IS_HASWELL(dev)) {
+               /*
+                * current versions of firmware which depend on this opregion
+                * notification have repurposed the D1 definition to mean
+                * "runtime suspended" vs. what you would normally expect (D3)
+                * to distinguish it from notifications that might be sent via
+                * the suspend path.
+                */
+               intel_opregion_notify_adapter(dev, PCI_D1);
+       } else {
+               /*
+                * On Broadwell, if we use PCI_D1 the PCH DDI ports will stop
+                * being detected, and the call we do at intel_runtime_resume()
+                * won't be able to restore them. Since PCI_D3hot matches the
+                * actual specification and appears to be working, use it. Let's
+                * assume the other non-Haswell platforms will stay the same as
+                * Broadwell.
+                */
+               intel_opregion_notify_adapter(dev, PCI_D3hot);
+       }
 
        DRM_DEBUG_KMS("Device suspended\n");
        return 0;