drm/i915/hsw, bdw: Add an ID for the global display power well

Add an ID for the HSW/BDW global display power well for consistency. The
ID is selected so that it can be used to get at the HW request and
status flags with the corresponding GEN9+ macros. Unifying the HSW/BDW
and GEN9+ versions of these macros and the power well ops using them
will be done in follow-up patches.

v2:
- Rebased on v2 of patch 2.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170711204236.5618-3-imre.deak@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -1097,6 +1097,12 @@ enum i915_power_well_id {
 	/*  - custom power well */
 	CHV_DISP_PW_PIPE_A,			/* 13 */
 
+	/*
+	 * HSW/BDW
+	 *  - HSW_PWR_WELL_DRIVER (status bit: id*2, req bit: id*2+1)
+	 */
+	HSW_DISP_PW_GLOBAL = 15,
+
 	/*
 	 * GEN9+
 	 *  - HSW_PWR_WELL_DRIVER (status bit: id*2, req bit: id*2+1)

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -2080,6 +2080,7 @@ static struct i915_power_well hsw_power_wells[] = {
 		.name = "display",
 		.domains = HSW_DISPLAY_POWER_DOMAINS,
 		.ops = &hsw_power_well_ops,
+		.id = HSW_DISP_PW_GLOBAL,
 	},
 };
 
@@ -2095,6 +2096,7 @@ static struct i915_power_well bdw_power_wells[] = {
 		.name = "display",
 		.domains = BDW_DISPLAY_POWER_DOMAINS,
 		.ops = &hsw_power_well_ops,
+		.id = HSW_DISP_PW_GLOBAL,
 	},
 };