drm/i915: disable VGA plane reliably

This does VGA disable like DDX driver. SR01 bit 5 should be set
before VGA plane disable through control register, otherwise we
might get random crash and lockups.

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 25 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a58bfadabd6..b06364ed259 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -998,6 +998,29 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
         return 0;
 }
 
+/* Disable the VGA plane that we never use */
+static void i915_disable_vga (struct drm_device *dev)
+{
+        struct drm_i915_private *dev_priv = dev->dev_private;
+        u8 sr1;
+        u32 vga_reg;
+
+        if (IS_IGDNG(dev))
+                vga_reg = CPU_VGACNTRL;
+        else
+                vga_reg = VGACNTRL;
+
+        if (I915_READ(vga_reg) & VGA_DISP_DISABLE)
+                return;
+
+        I915_WRITE8(VGA_SR_INDEX, 1);
+        sr1 = I915_READ8(VGA_SR_DATA);
+        I915_WRITE8(VGA_SR_DATA, sr1 | (1 << 5));
+        udelay(100);
+
+        I915_WRITE(vga_reg, VGA_DISP_DISABLE);
+}
+
 static void igdng_crtc_dpms(struct drm_crtc *crtc, int mode)
 {
         struct drm_device *dev = crtc->dev;
@@ -1200,8 +1223,7 @@ static void igdng_crtc_dpms(struct drm_crtc *crtc, int mode)
         case DRM_MODE_DPMS_OFF:
                 DRM_DEBUG("crtc %d dpms off\n", pipe);
 
-                /* Disable the VGA plane that we never use */
-                I915_WRITE(CPU_VGACNTRL, VGA_DISP_DISABLE);
+                i915_disable_vga(dev);
 
                 /* Disable display plane */
                 temp = I915_READ(dspcntr_reg);
@@ -1342,7 +1364,7 @@ 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);
+                i915_disable_vga(dev);
 
                 /* Disable display plane */
                 temp = I915_READ(dspcntr_reg);