[Intel-gfx] [PATCH v4 0/5] HPD support during suspend for BXT/APL.

[Animesh Manna]

Along with below patches sharing some background details/design.
- On BXT, Display cannot generate an interrupt when in D3.
- Without display in D3, S0ix can be achieved, Power impact will be zero if d3 is blocked. PMCSR for Graphics/Display is irrelevant, as the power management for them is taken care by the PUNIT using RC6/DC9 hints and *not* through PMCSR write trigger.

So solution is based on below principles:
- Display should not be put into D3 for HPD to work.
- With D0+DC9 we can achieve S0ix and at the same time helps to get the interrupt.
- Using pci_save_state() during suspend to take control from OSPM and blocking D3, while resuming, giving back to OSPM by pci_restore_state(). 
- _DSM method is used to program pmc hpd control register to enable hpd during suspend.

Please have a look and send your comments/suggestions.

v1: Initial version sent as RFC.

v2: Updated version after addressing review comments from Imre,David.

v3: Updated version after addressing review commnets from Imre, Ville,
    Chris.

v4: New version updated after bios changes on APL platform.

Animesh Manna (5):
  drm/i915/bxt: Corrected the guid for bxt.
  drm/i915/bxt: VBT changes for hpd as wakeup feature
  drm/i915/bxt: Added _DSM call to set HPD_CTL.
  drm/i915/bxt: Block D3 during suspend.
  drm/i915: Enable HPD interrupts with master ctl interrupt

 drivers/gpu/drm/i915/i915_drv.c         |  5 +++
 drivers/gpu/drm/i915/i915_drv.h         |  3 ++
 drivers/gpu/drm/i915/i915_irq.c         | 69 +++++++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/i915_reg.h         |  8 ++++
 drivers/gpu/drm/i915/intel_acpi.c       | 59 ++++++++++++++++++++++++----
 drivers/gpu/drm/i915/intel_bios.c       |  4 ++
 drivers/gpu/drm/i915/intel_runtime_pm.c |  3 +-
 drivers/gpu/drm/i915/intel_vbt_defs.h   |  3 +-
 8 files changed, 141 insertions(+), 13 deletions(-)

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1.9.1