[Intel-gfx] [PATCH V2] drm/i915: Disable VGA plane reliably

[ling.ma at intel.com]

VGA random hang on recent G45/43 board. From spec, SR01
bit 5 should be set before VGA plane disable through
control register, otherwise we might get random crash
and lockups.

sync up with 2D driver which fixed freedesktop.org bug #17235

Signed-off-by: Ma Ling <ling.ma at intel.com>
---
clean up work in this version

 drivers/gpu/drm/i915/i915_reg.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |   30 +++++++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 897a116..563e01c 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1767,6 +1767,7 @@
 # define VGA_DISP_DISABLE			(1 << 31)
 # define VGA_2X_MODE				(1 << 30)
 # define VGA_PIPE_B_SELECT			(1 << 29)
+# define VGA_CENTER_ENABLE			(3 << 24)
 
 /* IGDNG */
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a58bfad..a10a303 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1281,6 +1281,34 @@ static void igdng_crtc_dpms(struct drm_crtc *crtc, int mode)
 	}
 }
 
+static void
+intel_crtc_disable_vga_plane(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int vgacntrl = I915_READ(VGACNTRL);
+	uint8_t sr01;
+
+	if (vgacntrl & VGA_DISP_DISABLE)
+		return;
+	/*
+	 * Set SR01_SCREEN_OFF of SR1 register;
+	 * Wait 30us;
+	 */
+
+	I915_WRITE8(SRX_INDEX, SR01);
+	sr01 = I915_READ8(SRX_DATA);
+	I915_WRITE8(SRX_DATA, sr01 | SR01_SCREEN_OFF);
+	udelay(30);
+	/* disable center mode on 965GM and G4X platform */
+	if (IS_I965GM(dev) || IS_G4X(dev))
+		vgacntrl &= ~VGA_CENTER_ENABLE;
+	vgacntrl |= VGA_DISP_DISABLE;
+
+	I915_WRITE(VGACNTRL, vgacntrl);
+	intel_wait_for_vblank(dev);
+}
+
+
 static void i9xx_crtc_dpms(struct drm_crtc *crtc, int mode)
 {
 	struct drm_device *dev = crtc->dev;
@@ -1342,7 +1370,7 @@ static void i9xx_crtc_dpms(struct drm_crtc *crtc, int mode)
 		//intel_crtc_dpms_video(crtc, FALSE); TODO
 
 		/* Disable the VGA plane that we never use */
-		I915_WRITE(VGACNTRL, VGA_DISP_DISABLE);
+		intel_crtc_disable_vga_plane(dev);
 
 		/* Disable display plane */
 		temp = I915_READ(dspcntr_reg);
-- 
1.5.4.4