drm/i915: Ensure the HW is powered when disabling VGA

The assumption when adding the intel_display_power_is_enabled() checks
was that if it returns success the power can't be turned off afterwards
during the HW access, which is guaranteed by modeset locks. This isn't
always true, so make sure we hold a dedicated reference for the time of
the access.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1455296121-4742-5-git-send-email-imre.deak@intel.com
(cherry picked from commit 6392f8478e6f119467b1ad06e30e1f078e62efc1)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 46a84bb9ca1fe50784c9e1d5402748c7d76255ac..7934c45366ff26e92fec0c4d9811bbe591e8cbcc 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15599,10 +15599,12 @@ void i915_redisable_vga(struct drm_device *dev)
         * level, just check if the power well is enabled instead of trying to
         * follow the "don't touch the power well if we don't need it" policy
         * the rest of the driver uses. */
-       if (!intel_display_power_is_enabled(dev_priv, POWER_DOMAIN_VGA))
+       if (!intel_display_power_get_if_enabled(dev_priv, POWER_DOMAIN_VGA))
                return;
 
        i915_redisable_vga_power_on(dev);
+
+       intel_display_power_put(dev_priv, POWER_DOMAIN_VGA);
 }
 
 static bool primary_get_hw_state(struct intel_plane *plane)