drm/i915: Improve DP downstream HPD handling
authorVille Syrjälä <ville.syrjala@linux.intel.com>
Fri, 27 Oct 2017 09:45:23 +0000 (12:45 +0300)
committerVille Syrjälä <ville.syrjala@linux.intel.com>
Fri, 27 Oct 2017 19:14:46 +0000 (22:14 +0300)
DP dongles may signal downstream HPD via short HPD pulses. Setting the
sink to DPMS off apparently kills the downstream HPD (at least on my
DP->VGA dongle), so skip the DPMS off for such dongles when we turn
off the port.

v2: Deal with DDI as well by moving the check into
    intel_dp_sink_dpms() (Dhinakaran)

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Pablo <pablodebiase@nanalysis.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103472
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99114
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027094523.9317-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
drivers/gpu/drm/i915/intel_dp.c

index 73b1ed8..8d25a01 100644 (file)
@@ -2505,6 +2505,21 @@ static void ironlake_edp_pll_off(struct intel_dp *intel_dp)
        udelay(200);
 }
 
+static bool downstream_hpd_needs_d0(struct intel_dp *intel_dp)
+{
+       /*
+        * DPCD 1.2+ should support BRANCH_DEVICE_CTRL, and thus
+        * be capable of signalling downstream hpd with a long pulse.
+        * Whether or not that means D3 is safe to use is not clear,
+        * but let's assume so until proven otherwise.
+        *
+        * FIXME should really check all downstream ports...
+        */
+       return intel_dp->dpcd[DP_DPCD_REV] == 0x11 &&
+               intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT &&
+               intel_dp->downstream_ports[0] & DP_DS_PORT_HPD;
+}
+
 /* If the sink supports it, try to set the power state appropriately */
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
 {
@@ -2515,6 +2530,9 @@ void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
                return;
 
        if (mode != DRM_MODE_DPMS_ON) {
+               if (downstream_hpd_needs_d0(intel_dp))
+                       return;
+
                ret = drm_dp_dpcd_writeb(&intel_dp->aux, DP_SET_POWER,
                                         DP_SET_POWER_D3);
        } else {