drm/i915: Fix psr sink status report.

First of all don't try to read dpcd if PSR is not even supported.

But also, if read failed return -EIO instead of reporting via a
backchannel.

v2: fix dev_priv: At this level m->private is the connector. (CI/DK)
    don't convert dpcd read errors to EIO. (DK)

Fixes: 5b7b30864d1d ("drm/i915/psr: Split sink status into a separate debugfs node")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180720003155.16290-1-rodrigo.vivi@intel.com
(cherry picked from commit 7a72c78bdd0a1ea1d879610542679cc680398220)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index b3aefd623557..59dc0610ea44 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2606,13 +2606,22 @@ static int i915_psr_sink_status_show(struct seq_file *m, void *data)
                 "sink internal error",
         };
         struct drm_connector *connector = m->private;
+        struct drm_i915_private *dev_priv = to_i915(connector->dev);
         struct intel_dp *intel_dp =
                 enc_to_intel_dp(&intel_attached_encoder(connector)->base);
+        int ret;
+
+        if (!CAN_PSR(dev_priv)) {
+                seq_puts(m, "PSR Unsupported\n");
+                return -ENODEV;
+        }
 
         if (connector->status != connector_status_connected)
                 return -ENODEV;
 
-        if (drm_dp_dpcd_readb(&intel_dp->aux, DP_PSR_STATUS, &val) == 1) {
+        ret = drm_dp_dpcd_readb(&intel_dp->aux, DP_PSR_STATUS, &val);
+
+        if (ret == 1) {
                 const char *str = "unknown";
 
                 val &= DP_PSR_SINK_STATE_MASK;
@@ -2620,7 +2629,7 @@ static int i915_psr_sink_status_show(struct seq_file *m, void *data)
                         str = sink_status[val];
                 seq_printf(m, "Sink PSR status: 0x%x [%s]\n", val, str);
         } else {
-                DRM_ERROR("dpcd read (at %u) failed\n", DP_PSR_STATUS);
+                return ret;
         }
 
         return 0;