Re: [PATCH] drm/i915/psr: Split sink status into a separate debugfs node

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Thu, 2018-07-19 at 07:18 +0100, Chris Wilson wrote:
> Quoting Dhinakaran Pandiyan (2018-07-05 01:31:21)
> > 
> > This allows to read i915_edp_psr_status from tests without
> > triggering
> > any AUX communication. Take this opportunity to move this under the
> > eDP-1 connector directory as the status we print is of the sink.
> > 
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: José Roberto de Souza <jose.souza@intel.com>
> > Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 69 +++++++++++++++++++++--
> > --------------
> >  1 file changed, 39 insertions(+), 30 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
> > b/drivers/gpu/drm/i915/i915_debugfs.c
> > index f6142d78ede4..5069d5dedafe 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -2592,6 +2592,41 @@ static const struct file_operations
> > i915_guc_log_relay_fops = {
> >         .release = i915_guc_log_relay_release,
> >  };
> >  
> > +static int i915_psr_sink_status_show(struct seq_file *m, void
> > *data)
> > +{
> > +       u8 val;
> > +       static const char * const sink_status[] = {
> > +               "inactive",
> > +               "transition to active, capture and display",
> > +               "active, display from RFB",
> > +               "active, capture and display on sink device
> > timings",
> > +               "transition to inactive, capture and display,
> > timing re-sync",
> > +               "reserved",
> > +               "reserved",
> > +               "sink internal error",
> > +       };
> > +       struct drm_connector *connector = m->private;
> > +       struct intel_dp *intel_dp =
> > +               enc_to_intel_dp(&intel_attached_encoder(connector)-
> > >base);
> > +
> > +       if (connector->status != connector_status_connected)
> > +               return -ENODEV;
> > +
> > +       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_PSR_STATUS, &val)
> > == 1) {
> > +               const char *str = "unknown";
> > +
> > +               val &= DP_PSR_SINK_STATE_MASK;
> > +               if (val < ARRAY_SIZE(sink_status))
> > +                       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);
> Why is this common occurrence (any DP that doesn't support PSR) an
> error?
We create this file only for eDPs and I did not think dpcd_read would
return an error if the panel did not support PSR. Do you happen to have
any logs?

> Why report it via a backchannel when you are already directly
> communicating with the user?!!!
> 
You are right, i915_dpcd_show() also has the same issue. How about
returning the error to the user?  

@@ -2595,6 +2595,7 @@ static const struct file_operations
i915_guc_log_relay_fops = {
 static int i915_psr_sink_status_show(struct seq_file *m, void *data)
 {
        u8 val;
+       int ret;
        static const char * const sink_status[] = {
                "inactive",
                "transition to active, capture and display",
@@ -2605,6 +2606,7 @@ static int i915_psr_sink_status_show(struct
seq_file *m, void *data)
                "reserved",
                "sink internal error",
        };
+       const char *str = "unknown";
        struct drm_connector *connector = m->private;
        struct intel_dp *intel_dp =
                enc_to_intel_dp(&intel_attached_encoder(connector)-
>base);
@@ -2612,17 +2614,16 @@ static int i915_psr_sink_status_show(struct
seq_file *m, void *data)
        if (connector->status != connector_status_connected)
                return -ENODEV;

-       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_PSR_STATUS, &val) ==
1) {
-               const char *str = "unknown";
+       ret = drm_dp_dpcd_readb(&intel_dp->aux, DP_PSR_STATUS, &val);

+       if (ret < 0) {
+               return ret;
+       } else if (ret == 1) {
                val &= DP_PSR_SINK_STATE_MASK;
                if (val < ARRAY_SIZE(sink_status))
                        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);
        }
-
+       seq_printf(m, "Sink PSR status: 0x%x [%s]\n", val, str);
        return 0;
 }

> Please fix this mess.
> -Chris
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