From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: intel_pre_enable_dp
Date: Mon, 30 Sep 2013 01:48:13 +0200
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To: jbarnes@virtuousgeek.org
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Jesse,

I was playing with a static analyzer and it flagged the following
code of yours.

Is the val = 0 directly after the register read correct and intended?

commit 89b667f86a62a99a7b484a7e1b3f8f7a108a7dee
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Thu Apr 18 14:51:36 2013 -0700

    drm/i915: update VLV PLL and DPIO code v11
...

 static void intel_pre_enable_dp(struct intel_encoder *encoder)
 {
        struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
        struct drm_device *dev = encoder->base.dev;
+       struct drm_i915_private *dev_priv = dev->dev_private;
 
        if (is_cpu_edp(intel_dp) && !IS_VALLEYVIEW(dev))
                ironlake_edp_pll_on(intel_dp);
+
+       if (IS_VALLEYVIEW(dev)) {
+               struct intel_digital_port *dport = enc_to_dig_port(&encoder->base);
+               struct intel_crtc *intel_crtc =
+                       to_intel_crtc(encoder->base.crtc);
+               int port = vlv_dport_to_channel(dport);
+               int pipe = intel_crtc->pipe;
+               u32 val;
+
+               WARN_ON(!mutex_is_locked(&dev_priv->dpio_lock));
+
+               val = intel_dpio_read(dev_priv, DPIO_DATA_LANE_A(port));
+               val = 0;      <------------- val is directly overriden, previous value is ignored
+               if (pipe)
+                       val |= (1<<21);
+               else
+                       val &= ~(1<<21);





-- 
ak@linux.intel.com -- Speaking for myself only.