Re: [Intel-gfx] [PATCH 1/3] drm/i915: read sink_count dpcd always

[Sivakumar Thulasimani]

On 8/26/2015 3:17 PM, Jani Nikula wrote:

On Tue, 25 Aug 2015, Sivakumar Thulasimani <sivakumar.thulasim...@intel.com> 
wrote:

From: "Thulasimani,Sivakumar" <sivakumar.thulasim...@intel.com>

This patch reads sink_count dpcd always and removes its
read operation based on values in downstream port dpcd. Also
we should read it irrespective of current status of sink.

Having to write "also" in a commit message is a good hint to stop and
think about whether that should be a separate patch. Maybe it should be,
here too?

BR,
Jani.

:) i thought about it since that part of the message was added last, since
without those changes this patch will not be "read sink_count always".

will split it into two patches and rename them accordingly.

SINK_COUNT dpcd is not dependent on DOWNSTREAM_PORT_PRESENT dpcd.
SINK_COUNT denotes if a display is attached, while
DOWNSTREAM_PORT_PRESET indicates how many ports are available
in the dongle where display can be attached. so it is possible
for sink count to change irrespective of value in downstream
port dpcd.

Here is a table of possible values and scenarios

sink_count      downstream_port
                present
0               0               no display is attached
0               1               dongle is connected without display
1               0               display connected directly
1               1               display connected through dongle

Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasim...@intel.com>
---
  drivers/gpu/drm/i915/intel_dp.c |   33 ++++++++++++++-------------------
  1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8a66a44..9e4e27d 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3898,6 +3898,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
        struct drm_device *dev = dig_port->base.base.dev;
        struct drm_i915_private *dev_priv = dev->dev_private;
        uint8_t rev;
+       uint8_t reg;

if (intel_dp_dpcd_read_wake(&intel_dp->aux, 0x000, intel_dp->dpcd,

                                    sizeof(intel_dp->dpcd)) < 0)
@@ -3908,6 +3909,13 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
        if (intel_dp->dpcd[DP_DPCD_REV] == 0)
                return false; /* DPCD not present */

+ if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,

+                                           &reg, 1) < 0)
+                       return false;
+
+       if (!DP_GET_SINK_COUNT(reg))
+               return false;
+
        /* Check if the panel supports PSR */
        memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
        if (is_edp(intel_dp)) {
@@ -4374,12 +4382,6 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)

WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); - if (!intel_encoder->base.crtc)

-               return;
-
-       if (!to_intel_crtc(intel_encoder->base.crtc)->active)
-               return;
-
        /* Try to read receiver status if the link appears to be up */
        if (!intel_dp_get_link_status(intel_dp, link_status)) {
                return;
@@ -4390,6 +4392,12 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
                return;
        }

+ if (!intel_encoder->base.crtc)

+               return;
+
+       if (!to_intel_crtc(intel_encoder->base.crtc)->active)
+               return;
+
        /* Try to read the source of the interrupt */
        if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11 &&
            intel_dp_get_sink_irq(intel_dp, &sink_irq_vector)) {
@@ -4427,19 +4435,6 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
        if (!(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
                return connector_status_connected;

- /* If we're HPD-aware, SINK_COUNT changes dynamically */

-       if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11 &&
-           intel_dp->downstream_ports[0] & DP_DS_PORT_HPD) {
-               uint8_t reg;
-
-               if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
-                                           &reg, 1) < 0)
-                       return connector_status_unknown;
-
-               return DP_GET_SINK_COUNT(reg) ? connector_status_connected
-                                             : connector_status_disconnected;
-       }
-
        /* If no HPD, poke DDC gently */
        if (drm_probe_ddc(&intel_dp->aux.ddc))
                return connector_status_connected;
--
1.7.9.5

--
regards,
Sivakumar

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