drm/i915/vlv: Disable HPD in valleyview_crt_detect_hotplug()
One of the things preventing us from using polling is the fact that
calling valleyview_crt_detect_hotplug() when there's a VGA cable
connected results in sending another hotplug. With polling enabled when
HPD is disabled, this results in a scenario like this:
- We enable power wells and reset the ADPA
- output_poll_exec does force probe on VGA, triggering a hpd
- HPD handler waits for poll to unlock dev->mode_config.mutex
- output_poll_exec shuts off the ADPA, unlocks dev->mode_config.mutex
- HPD handler runs, resets ADPA and brings us back to the start
This results in an endless irq storm getting sent from the ADPA
whenever a VGA connector gets detected in the middle of polling.
Somewhat based off of the "drm/i915: Disable CRT HPD around force
trigger" patch Ville Syrjälä sent a while back
Cc: stable@vger.kernel.org
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Lyude <cpaul@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index d172930a..827b6ef 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -329,10 +329,25 @@
struct drm_device *dev = connector->dev;
struct intel_crt *crt = intel_attached_crt(connector);
struct drm_i915_private *dev_priv = to_i915(dev);
+ bool reenable_hpd;
u32 adpa;
bool ret;
u32 save_adpa;
+ /*
+ * Doing a force trigger causes a hpd interrupt to get sent, which can
+ * get us stuck in a loop if we're polling:
+ * - We enable power wells and reset the ADPA
+ * - output_poll_exec does force probe on VGA, triggering a hpd
+ * - HPD handler waits for poll to unlock dev->mode_config.mutex
+ * - output_poll_exec shuts off the ADPA, unlocks
+ * dev->mode_config.mutex
+ * - HPD handler runs, resets ADPA and brings us back to the start
+ *
+ * Just disable HPD interrupts here to prevent this
+ */
+ reenable_hpd = intel_hpd_disable(dev_priv, crt->base.hpd_pin);
+
save_adpa = adpa = I915_READ(crt->adpa_reg);
DRM_DEBUG_KMS("trigger hotplug detect cycle: adpa=0x%x\n", adpa);
@@ -357,6 +372,9 @@
DRM_DEBUG_KMS("valleyview hotplug adpa=0x%x, result %d\n", adpa, ret);
+ if (reenable_hpd)
+ intel_hpd_enable(dev_priv, crt->base.hpd_pin);
+
return ret;
}