Re: [PATCH] drm/amd/display: Add aconnector condition check for dpcd read

["Gravenor, Joseph" <Joseph.Gravenor@amd.com>]

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[AMD Official Use Only - Internal Distribution Only]

Reviewed-by: Joseph Gravenor <Joseph.Gravenor@amd.com>

________________________________
From: Liu, Zhan <Zhan.Liu@amd.com>
Sent: Monday, February 10, 2020 4:08 PM
To: amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; Liu, Zhan <Zhan.Liu@amd.com>; Gravenor, Joseph <Joseph.Gravenor@amd.com>
Subject: [PATCH] drm/amd/display: Add aconnector condition check for dpcd read

[Why]
core_link_read_dpcd() will invoke dm_helpers_dp_read_dpcd(),
which needs to read dpcd info with the help of aconnector.
If aconnector (dc->links[i]->prev) is NULL, then dpcd status
 cannot be read.

As a result, dpcd read fails and a line of error will be
printed out in dmesg.log as:
"*ERROR* Failed to found connector for link!"

[How]
Make sure that aconnector (dc->links[i]->prev) is not NULL,
then read dpcd status.

Signed-off-by: Zhan Liu <zhan.liu@amd.com>
---
 .../amd/display/dc/dcn10/dcn10_hw_sequencer.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
index 42fcfee2c31b..92e1574073fd 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
@@ -1331,11 +1331,20 @@ void dcn10_init_hw(struct dc *dc)
                         if (dc->links[i]->connector_signal != SIGNAL_TYPE_DISPLAY_PORT) {
                                 continue;
                         }
-                       /* if any of the displays are lit up turn them off */
-                       status = core_link_read_dpcd(dc->links[i], DP_SET_POWER,
-                                                    &dpcd_power_state, sizeof(dpcd_power_state));
-                       if (status == DC_OK && dpcd_power_state == DP_POWER_STATE_D0) {
-                               dp_receiver_power_ctrl(dc->links[i], false);
+
+                       /*
+                        * core_link_read_dpcd() will invoke dm_helpers_dp_read_dpcd(),
+                        * which needs to read dpcd info with the help of aconnector.
+                        * If aconnector (dc->links[i]->prev) is NULL, then dpcd status
+                        * cannot be read.
+                        */
+                       if (dc->links[i]->priv) {
+                               /* if any of the displays are lit up turn them off */
+                               status = core_link_read_dpcd(dc->links[i], DP_SET_POWER,
+                                                               &dpcd_power_state, sizeof(dpcd_power_state));
+                               if (status == DC_OK && dpcd_power_state == DP_POWER_STATE_D0) {
+                                       dp_receiver_power_ctrl(dc->links[i], false);
+                               }
                         }
                 }
         }
--
2.17.1


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