[PATCH] i915: ensure that VGA plane is disabled

[PATCH] i915: ensure that VGA plane is disabled

[Krzysztof Mazur]

Some broken systems (like HP nc6120) in some cases, usually after LID
close/open, enable VGA plane, making display unusable (black screen on LVDS,
some strange mode on VGA output). We used to disable VGA plane only once at
startup. Now we also check, if VGA plane is still disabled while changing
mode, and fix that if something changed it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=57434
Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
---
 drivers/gpu/drm/i915/intel_display.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 437b56a..ffc9715 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8712,6 +8712,23 @@ static void intel_sanitize_encoder(struct intel_encoder *encoder)
 	 * the crtc fixup. */
 }
 
+static void i915_redisable_vga(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 vga_reg;
+
+	if (HAS_PCH_SPLIT(dev))
+		vga_reg = CPU_VGACNTRL;
+	else
+		vga_reg = VGACNTRL;
+
+	if (I915_READ(vga_reg) != VGA_DISP_DISABLE) {
+		DRM_DEBUG_KMS("Something enabled VGA plane, disabling it\n");
+		I915_WRITE(vga_reg, VGA_DISP_DISABLE);
+		POSTING_READ(vga_reg);
+	}
+}
+
 /* Scan out the current hw modeset state, sanitizes it and maps it into the drm
  * and i915 state tracking structures. */
 void intel_modeset_setup_hw_state(struct drm_device *dev,
@@ -8820,6 +8837,8 @@ void intel_modeset_setup_hw_state(struct drm_device *dev,
 			intel_set_mode(&crtc->base, &crtc->base.mode,
 				       crtc->base.x, crtc->base.y, crtc->base.fb);
 		}
+
+		i915_redisable_vga(dev);
 	} else {
 		intel_modeset_update_staged_output_state(dev);
 	}
-- 
1.8.1.rc2

Re: [PATCH] i915: ensure that VGA plane is disabled

[Daniel Vetter]

On Wed, Dec 19, 2012 at 11:03:41AM +0100, Krzysztof Mazur wrote:
> Some broken systems (like HP nc6120) in some cases, usually after LID
> close/open, enable VGA plane, making display unusable (black screen on LVDS,
> some strange mode on VGA output). We used to disable VGA plane only once at
> startup. Now we also check, if VGA plane is still disabled while changing
> mode, and fix that if something changed it.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=57434
> Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>

*insert laments about BIOSen doing horrible things*

Thanks a lot for digging into this and coming up with the patch, merged to
-fixes for 3.8 with a cc: stable, so should show up reasonable quickly in
a stable kernel near you.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch