drm/i915: Try to reset gen2 devices.

So far only found registers for i830, i845, i865 and one of those has no
effect on i865!

At this moment in time, attempting to reset i8xx is a little
optimistic...
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.c

@@ -342,6 +342,36 @@ int i915_resume(struct drm_device *dev)
 	return 0;
 }
 
+static int i8xx_do_reset(struct drm_device *dev, u8 flags)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (IS_I85X(dev))
+		return -ENODEV;
+
+	I915_WRITE(D_STATE, I915_READ(D_STATE) | DSTATE_GFX_RESET_I830);
+	POSTING_READ(D_STATE);
+
+	if (IS_I830(dev) || IS_845G(dev)) {
+		I915_WRITE(DEBUG_RESET_I830,
+			   DEBUG_RESET_DISPLAY |
+			   DEBUG_RESET_RENDER |
+			   DEBUG_RESET_FULL);
+		POSTING_READ(DEBUG_RESET_I830);
+		msleep(1);
+
+		I915_WRITE(DEBUG_RESET_I830, 0);
+		POSTING_READ(DEBUG_RESET_I830);
+	}
+
+	msleep(1);
+
+	I915_WRITE(D_STATE, I915_READ(D_STATE) & ~DSTATE_GFX_RESET_I830);
+	POSTING_READ(D_STATE);
+
+	return 0;
+}
+
 static int i965_reset_complete(struct drm_device *dev)
 {
 	u8 gdrst;
@@ -410,6 +440,9 @@ int i915_reset(struct drm_device *dev, u8 flags)
 	case 4:
 		ret = i965_do_reset(dev, flags);
 		break;
+	case 2:
+		ret = i8xx_do_reset(dev, flags);
+		break;
 	}
 	if (ret) {
 		DRM_ERROR("Failed to reset chip.\n");

drivers/gpu/drm/i915/i915_reg.h

@@ -216,6 +216,16 @@
 #define   PIPE_CONTROL_GLOBAL_GTT (1<<2) /* in addr dword */
 #define   PIPE_CONTROL_STALL_EN	(1<<1) /* in addr word, Ironlake+ only */
 
+
+/*
+ * Reset registers
+ */
+#define DEBUG_RESET_I830		0x6070
+#define  DEBUG_RESET_FULL		(1<<7)
+#define  DEBUG_RESET_RENDER		(1<<8)
+#define  DEBUG_RESET_DISPLAY		(1<<9)
+
+
 /*
  * Fence registers
  */
@@ -763,6 +773,7 @@
 #define   DPLLA_TEST_M_BYPASS		(1 << 2)
 #define   DPLLA_INPUT_BUFFER_ENABLE	(1 << 0)
 #define D_STATE		0x6104
+#define  DSTATE_GFX_RESET_I830			(1<<6)
 #define  DSTATE_PLL_D3_OFF			(1<<3)
 #define  DSTATE_GFX_CLOCK_GATING		(1<<1)
 #define  DSTATE_DOT_CLOCK_GATING		(1<<0)