drm/i915: allow package C8+ states on Haswell (disabled)

This patch allows PC8+ states on Haswell. These states can only be
reached when all the display outputs are disabled, and they allow some
more power savings.

The fact that the graphics device is allowing PC8+ doesn't mean that
the machine will actually enter PC8+: all the other devices also need
to allow PC8+.

For now this option is disabled by default. You need i915.allow_pc8=1
if you want it.

This patch adds a big comment inside i915_drv.h explaining how it
works and how it tracks things. Read it.

v2: (this is not really v2, many previous versions were already sent,
     but they had different names)
    - Use the new functions to enable/disable GTIMR and GEN6_PMIMR
    - Rename almost all variables and functions to names suggested by
      Chris
    - More WARNs on the IRQ handling code
    - Also disable PC8 when there's GPU work to do (thanks to Ben for
      the help on this), so apps can run caster
    - Enable PC8 on a delayed work function that is delayed for 5
      seconds. This makes sure we only enable PC8+ if we're really
      idle
    - Make sure we're not in PC8+ when suspending
v3: - WARN if IRQs are disabled on __wait_seqno
    - Replace some DRM_ERRORs with WARNs
    - Fix calls to restore GT and PM interrupts
    - Use intel_mark_busy instead of intel_ring_advance to disable PC8
v4: - Use the force_wake, Luke!
v5: - Remove the "IIR is not zero" WARNs
    - Move the force_wake chunk to its own patch
    - Only restore what's missing from RC6, not everything

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index cbab95dce352..0150ba598bf0 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3607,7 +3607,7 @@ static void gen6_enable_rps(struct drm_device *dev)
 	gen6_gt_force_wake_put(dev_priv);
 }
 
-static void gen6_update_ring_freq(struct drm_device *dev)
+void gen6_update_ring_freq(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int min_freq = 15;
@@ -5398,6 +5398,17 @@ void intel_init_power_well(struct drm_device *dev)
 		I915_WRITE(HSW_PWR_WELL_BIOS, 0);
 }
 
+/* Disables PC8 so we can use the GMBUS and DP AUX interrupts. */
+void intel_aux_display_runtime_get(struct drm_i915_private *dev_priv)
+{
+	hsw_disable_package_c8(dev_priv);
+}
+
+void intel_aux_display_runtime_put(struct drm_i915_private *dev_priv)
+{
+	hsw_enable_package_c8(dev_priv);
+}
+
 /* Set up chip specific power management-related functions */
 void intel_init_pm(struct drm_device *dev)
 {