drm/i915/lvds: Ensure the HW is powered during HW state readout

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/1455296121-4742-13-git-send-email-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 811ddf7799f0c0f381ac650f64b166c2a17c812a..30a8403a8f4fbaa25e8f55ca3655596bc298768e 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -76,22 +76,30 @@ static bool intel_lvds_get_hw_state(struct intel_encoder *encoder,
        struct intel_lvds_encoder *lvds_encoder = to_lvds_encoder(&encoder->base);
        enum intel_display_power_domain power_domain;
        u32 tmp;
+       bool ret;
 
        power_domain = intel_display_port_power_domain(encoder);
-       if (!intel_display_power_is_enabled(dev_priv, power_domain))
+       if (!intel_display_power_get_if_enabled(dev_priv, power_domain))
                return false;
 
+       ret = false;
+
        tmp = I915_READ(lvds_encoder->reg);
 
        if (!(tmp & LVDS_PORT_EN))
-               return false;
+               goto out;
 
        if (HAS_PCH_CPT(dev))
                *pipe = PORT_TO_PIPE_CPT(tmp);
        else
                *pipe = PORT_TO_PIPE(tmp);
 
-       return true;
+       ret = true;
+
+out:
+       intel_display_power_put(dev_priv, power_domain);
+
+       return ret;
 }
 
 static void intel_lvds_get_config(struct intel_encoder *encoder,