drm/i915/vlv: Turn off power gate for BIOS-less system.

During system boot up, by default, the power gate for render, media and
display well still power gated.  Normally, BIOS will turn off the power
gate.  In the BIOS-less system, the driver need to turn off the power
gate very early during driver load.

v2: Move this to intel_uncore_sanitize to allow it to get call during
resume path. (Daniel)
v3: Remove redundant write 0 to DPIO_CTL, and use DPIO_RESET instead of
just 0x1 (Ville)
    Add turn of power gate for display 2d/render well/media well.
v4: Remove toggle cmnreset in intel_uncore_sanitize.  Cmnreset should
toggle after CRI clock source has been selected.  Jesse DPIO reset patch
which toggle the cmnreset in intel_modeset_init_hw() should handle it.
(Ville)

Signed-off-by: Chon Ming Lee <chon.ming.lee@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -361,6 +361,15 @@
 #define PUNIT_OPCODE_REG_READ			6
 #define PUNIT_OPCODE_REG_WRITE			7
 
+#define PUNIT_REG_PWRGT_CTRL			0x60
+#define PUNIT_REG_PWRGT_STATUS			0x61
+#define	  PUNIT_CLK_GATE			1
+#define	  PUNIT_PWR_RESET			2
+#define	  PUNIT_PWR_GATE			3
+#define	  RENDER_PWRGT				(PUNIT_PWR_GATE << 0)
+#define	  MEDIA_PWRGT				(PUNIT_PWR_GATE << 2)
+#define	  DISP2D_PWRGT				(PUNIT_PWR_GATE << 6)
+
 #define PUNIT_REG_GPU_LFM			0xd3
 #define PUNIT_REG_GPU_FREQ_REQ			0xd4
 #define PUNIT_REG_GPU_FREQ_STS			0xd8

drivers/gpu/drm/i915/intel_uncore.c

@@ -301,10 +301,26 @@ static void intel_uncore_forcewake_reset(struct drm_device *dev)
 
 void intel_uncore_sanitize(struct drm_device *dev)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 reg_val;
+
 	intel_uncore_forcewake_reset(dev);
 
 	/* BIOS often leaves RC6 enabled, but disable it for hw init */
 	intel_disable_gt_powersave(dev);
+
+	/* Turn off power gate, require especially for the BIOS less system */
+	if (IS_VALLEYVIEW(dev)) {
+
+		mutex_lock(&dev_priv->rps.hw_lock);
+		reg_val = vlv_punit_read(dev_priv, PUNIT_REG_PWRGT_STATUS);
+
+		if (reg_val & (RENDER_PWRGT | MEDIA_PWRGT | DISP2D_PWRGT))
+			vlv_punit_write(dev_priv, PUNIT_REG_PWRGT_CTRL, 0x0);
+
+		mutex_unlock(&dev_priv->rps.hw_lock);
+
+	}
 }
 
 /*