[PATCH 11/15] drm/amd/display: add a debug option to force dp2 lt fallback method

[Pavle Kotarac]

From: Wenjing Liu <wenjing....@amd.com>

[why]
A debug option is needed to temporarily force dp2 new link training
fallback method for debugging purpose.

Reviewed-by: George Shen <george.s...@amd.com>
Acked-by: Pavle Kotarac <pavle.kota...@amd.com>
Signed-off-by: Wenjing Liu <wenjing....@amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 9 ++++++---
 drivers/gpu/drm/amd/display/dc/dc.h              | 1 +
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c 
b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index f1898f1c9e22..56e141fb2694 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -100,6 +100,7 @@ static const struct dp_lt_fallback_entry dp_lt_fallbacks[] 
= {
 #endif
 
 static bool decide_fallback_link_setting(
+               struct dc_link *link,
                struct dc_link_settings initial_link_settings,
                struct dc_link_settings *current_link_setting,
                enum link_training_result training_result);
@@ -2609,7 +2610,7 @@ bool perform_link_training_with_retries(
                        uint32_t req_bw;
                        uint32_t link_bw;
 
-                       decide_fallback_link_setting(*link_setting, 
&current_setting, status);
+                       decide_fallback_link_setting(link, *link_setting, 
&current_setting, status);
                        /* Fail link training if reduced link bandwidth no 
longer meets
                         * stream requirements.
                         */
@@ -3124,7 +3125,7 @@ bool dp_verify_link_cap(
                 * based on the actual mode we're driving
                 */
                dp_disable_link_phy(link, link->connector_signal);
-       } while (!success && decide_fallback_link_setting(
+       } while (!success && decide_fallback_link_setting(link,
                        initial_link_settings, cur, status));
 
        /* Link Training failed for all Link Settings
@@ -3376,6 +3377,7 @@ static bool decide_fallback_link_setting_max_bw_policy(
  *                                     and no further fallback could be done
  */
 static bool decide_fallback_link_setting(
+               struct dc_link *link,
                struct dc_link_settings initial_link_settings,
                struct dc_link_settings *current_link_setting,
                enum link_training_result training_result)
@@ -3383,7 +3385,8 @@ static bool decide_fallback_link_setting(
        if (!current_link_setting)
                return false;
 #if defined(CONFIG_DRM_AMD_DC_DCN)
-       if (dp_get_link_encoding_format(&initial_link_settings) == 
DP_128b_132b_ENCODING)
+       if (dp_get_link_encoding_format(&initial_link_settings) == 
DP_128b_132b_ENCODING ||
+                       link->dc->debug.force_dp2_lt_fallback_method)
                return 
decide_fallback_link_setting_max_bw_policy(&initial_link_settings,
                                current_link_setting);
 #endif
diff --git a/drivers/gpu/drm/amd/display/dc/dc.h 
b/drivers/gpu/drm/amd/display/dc/dc.h
index 5c2cb892d993..a43c008bd0f2 100644
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -691,6 +691,7 @@ struct dc_debug_options {
        /* TODO - remove once tested */
        bool legacy_dp2_lt;
        bool set_mst_en_for_sst;
+       bool force_dp2_lt_fallback_method;
 #endif
        union mem_low_power_enable_options enable_mem_low_power;
        union root_clock_optimization_options root_clock_optimization;
-- 
2.32.0