drm/i915: Warn if a pipe is enabled with a bogus port

If TRANS_DDI_FUNC_CTL has been wrongly programmed with an incorrect
port, we are currently trying to read PORT_CLK_SEL(port) with an
uninitialized value.

Handle that case by returning PORT_CLK_SEL_NONE and warning about it.

v2: Move the warning inside intel_ddi_get_crtc_pll (Paulo Zanoni)

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index d26147c..258e38e 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1160,7 +1160,7 @@ static uint32_t intel_ddi_get_crtc_pll(struct drm_i915_private *dev_priv,
                                       enum pipe pipe)
 {
        uint32_t temp, ret;
-       enum port port;
+       enum port port = I915_MAX_PORTS;
        enum transcoder cpu_transcoder = intel_pipe_to_cpu_transcoder(dev_priv,
                                                                      pipe);
        int i;
@@ -1176,10 +1176,16 @@ static uint32_t intel_ddi_get_crtc_pll(struct drm_i915_private *dev_priv,
                                port = i;
        }
 
-       ret = I915_READ(PORT_CLK_SEL(port));
-
-       DRM_DEBUG_KMS("Pipe %c connected to port %c using clock 0x%08x\n",
-                     pipe_name(pipe), port_name(port), ret);
+       if (port == I915_MAX_PORTS) {
+               WARN(1, "Pipe %c enabled on an unknown port\n",
+                    pipe_name(pipe));
+               ret = PORT_CLK_SEL_NONE;
+       } else {
+               ret = I915_READ(PORT_CLK_SEL(port));
+               DRM_DEBUG_KMS("Pipe %c connected to port %c using clock "
+                             "0x%08x\n", pipe_name(pipe), port_name(port),
+                             ret);
+       }
 
        return ret;
 }