drm/i915: make DP work on LPT-LP machines

We need to enable a special bit, otherwise none of the DP functions
requiring the PCH will work.

Version 2: store the PCH ID inside dev_priv, as suggested by Daniel
Vetter.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -396,13 +396,6 @@ static const struct pci_device_id pciidlist[] = {		/* aka */
 MODULE_DEVICE_TABLE(pci, pciidlist);
 #endif
 
-#define INTEL_PCH_DEVICE_ID_MASK	0xff00
-#define INTEL_PCH_IBX_DEVICE_ID_TYPE	0x3b00
-#define INTEL_PCH_CPT_DEVICE_ID_TYPE	0x1c00
-#define INTEL_PCH_PPT_DEVICE_ID_TYPE	0x1e00
-#define INTEL_PCH_LPT_DEVICE_ID_TYPE	0x8c00
-#define INTEL_PCH_LPT_LP_DEVICE_ID_TYPE	0x9c00
-
 void intel_detect_pch(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -417,8 +410,9 @@ void intel_detect_pch(struct drm_device *dev)
 	pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);
 	if (pch) {
 		if (pch->vendor == PCI_VENDOR_ID_INTEL) {
-			int id;
+			unsigned short id;
 			id = pch->device & INTEL_PCH_DEVICE_ID_MASK;
+			dev_priv->pch_id = id;
 
 			if (id == INTEL_PCH_IBX_DEVICE_ID_TYPE) {
 				dev_priv->pch_type = PCH_IBX;

drivers/gpu/drm/i915/i915_drv.h

@@ -737,6 +737,7 @@ typedef struct drm_i915_private {
 
 	/* PCH chipset type */
 	enum intel_pch pch_type;
+	unsigned short pch_id;
 
 	unsigned long quirks;
 
@@ -1205,6 +1206,13 @@ struct drm_i915_file_private {
 
 #define HAS_PIPE_CONTROL(dev) (INTEL_INFO(dev)->gen >= 5)
 
+#define INTEL_PCH_DEVICE_ID_MASK		0xff00
+#define INTEL_PCH_IBX_DEVICE_ID_TYPE		0x3b00
+#define INTEL_PCH_CPT_DEVICE_ID_TYPE		0x1c00
+#define INTEL_PCH_PPT_DEVICE_ID_TYPE		0x1e00
+#define INTEL_PCH_LPT_DEVICE_ID_TYPE		0x8c00
+#define INTEL_PCH_LPT_LP_DEVICE_ID_TYPE		0x9c00
+
 #define INTEL_PCH_TYPE(dev) (((struct drm_i915_private *)(dev)->dev_private)->pch_type)
 #define HAS_PCH_LPT(dev) (INTEL_PCH_TYPE(dev) == PCH_LPT)
 #define HAS_PCH_CPT(dev) (INTEL_PCH_TYPE(dev) == PCH_CPT)

drivers/gpu/drm/i915/i915_reg.h

@@ -3851,6 +3851,7 @@
 
 #define SOUTH_DSPCLK_GATE_D	0xc2020
 #define  PCH_DPLSUNIT_CLOCK_GATE_DISABLE (1<<29)
+#define  PCH_LP_PARTITION_LEVEL_DISABLE  (1<<12)
 
 /* CPU: FDI_TX */
 #define _FDI_TXA_CTL             0x60100

drivers/gpu/drm/i915/intel_pm.c

@@ -3549,6 +3549,20 @@ static void gen7_setup_fixed_func_scheduler(struct drm_i915_private *dev_priv)
 	I915_WRITE(GEN7_FF_THREAD_MODE, reg);
 }
 
+static void lpt_init_clock_gating(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	/*
+	 * TODO: this bit should only be enabled when really needed, then
+	 * disabled when not needed anymore in order to save power.
+	 */
+	if (dev_priv->pch_id == INTEL_PCH_LPT_LP_DEVICE_ID_TYPE)
+		I915_WRITE(SOUTH_DSPCLK_GATE_D,
+			   I915_READ(SOUTH_DSPCLK_GATE_D) |
+			   PCH_LP_PARTITION_LEVEL_DISABLE);
+}
+
 static void haswell_init_clock_gating(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -3600,6 +3614,7 @@ static void haswell_init_clock_gating(struct drm_device *dev)
 			WM_DBG_DISALLOW_SPRITE |
 			WM_DBG_DISALLOW_MAXFIFO);
 
+	lpt_init_clock_gating(dev);
 }
 
 static void ivybridge_init_clock_gating(struct drm_device *dev)