[PATCH 1/5] drm/i915: redisable VGA when we disable the power well

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

VGA whack-a-mole!

We need VGA to be disabled whenever our driver is working. So even
without reproducible bugs this patch makes sense, but we do have a bug
solved by this patch.

If you boot a Haswell machine with eDP+HDMI, then kill your display
manager and run:
    echo 0 > /sys/class/vtconsole/vtcon1/bind
you'll get thousands of "unclaimed register" messages. Notice that
since we have eDP+HDMI, the power well is *enabled* when we run the
command, but if you look at dmesg you'll see that at some point during
the boot we disabled it and then reenabled it. This patch solves this
problem.

I didn't do a deep analysis of the problem, but I guess vgacon gets
seriously confused when it sees that the VGA plane is enabled.

Besides the command above, this problem can also be reproduced by the
"module_reload" test from intel-gpu-tools.

Fixes regression introduced by:
    commit bf51d5e2cda5d36d98e4b46ac7fca9461e512c41
    Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
        drm/i915: switch disable_power_well default value to 1

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67813
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 2 +-
 drivers/gpu/drm/i915/intel_drv.h     | 1 +
 drivers/gpu/drm/i915/intel_pm.c      | 6 ++++++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 665fa8f..065ffed 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10232,7 +10232,7 @@ static void intel_init_quirks(struct drm_device *dev)
 }
 
 /* Disable the VGA plane that we never use */
-static void i915_disable_vga(struct drm_device *dev)
+void i915_disable_vga(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u8 sr1;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index a17a86a..e63646a 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -678,6 +678,7 @@ void
 ironlake_check_encoder_dotclock(const struct intel_crtc_config *pipe_config,
 				int dotclock);
 bool intel_crtc_active(struct drm_crtc *crtc);
+void i915_disable_vga(struct drm_device *dev);
 void i915_disable_vga_mem(struct drm_device *dev);
 
 
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2ac1c2f..7a8af95 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5329,6 +5329,12 @@ static void __intel_set_power_well(struct drm_device *dev, bool enable)
 			if (wait_for((I915_READ(HSW_PWR_WELL_DRIVER) &
 				      HSW_PWR_WELL_STATE_ENABLED), 20))
 				DRM_ERROR("Timeout enabling power well\n");
+
+			if (I915_READ(i915_vgacntrl_reg(dev)) !=
+			    VGA_DISP_DISABLE) {
+				i915_disable_vga(dev);
+				i915_disable_vga_mem(dev);
+			}
 		}
 	} else {
 		if (enable_requested) {
-- 
1.8.3.1