[PATCH 12/16] drm/amd/display: Skip vendor specific LTTPR w/a outside link training

[Bhawanpreet Lakha]

From: George Shen <george.s...@amd.com>

[Why]
Vendor specific link rate toggle workaround should not be
applied outside of link training scenario, such as when
outputting PHY test pattern.

[How]
Add flag to indicate when link training is occuring.
Make workaround a no-op when flag is not set.

Reviewed-by: Jun Lei <jun....@amd.com>
Acked-by: Bhawanpreet Lakha <bhawanpreet.la...@amd.com>
Signed-off-by: George Shen <george.s...@amd.com>
---
 .../gpu/drm/amd/display/dc/core/dc_link_dp.c  | 44 +++++++++++--------
 drivers/gpu/drm/amd/display/dc/dc_link.h      |  1 +
 2 files changed, 26 insertions(+), 19 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 5eea4ec82f99..026ce0839719 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
@@ -444,24 +444,26 @@ static void vendor_specific_lttpr_wa_one_two(
        struct dc_link *link,
        const uint8_t rate)
 {
-       uint8_t toggle_rate = 0x0;
+       if (link->apply_vendor_specific_lttpr_link_rate_wa) {
+               uint8_t toggle_rate = 0x0;
 
-       if (rate == 0x6)
-               toggle_rate = 0xA;
-       else
-               toggle_rate = 0x6;
+               if (rate == 0x6)
+                       toggle_rate = 0xA;
+               else
+                       toggle_rate = 0x6;
 
-       if (link->vendor_specific_lttpr_link_rate_wa == rate) {
-               /* W/A for certain LTTPR to reset internal state for link 
training */
-               core_link_write_dpcd(
-                               link,
-                               DP_LINK_BW_SET,
-                               &toggle_rate,
-                               1);
-       }
+               if (link->vendor_specific_lttpr_link_rate_wa == rate) {
+                       /* W/A for certain LTTPR to reset internal state for 
link training */
+                       core_link_write_dpcd(
+                                       link,
+                                       DP_LINK_BW_SET,
+                                       &toggle_rate,
+                                       1);
+               }
 
-       /* Store the last attempted link rate for this link */
-       link->vendor_specific_lttpr_link_rate_wa = rate;
+               /* Store the last attempted link rate for this link */
+               link->vendor_specific_lttpr_link_rate_wa = rate;
+       }
 }
 
 static void vendor_specific_lttpr_wa_three(
@@ -2383,10 +2385,12 @@ enum link_training_result 
dc_link_dp_perform_link_training(
        /* reset previous training states */
        if (link->dc->debug.apply_vendor_specific_lttpr_wa &&
                        (link->chip_caps & 
EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN) &&
-                       link->lttpr_mode == LTTPR_MODE_TRANSPARENT)
+                       link->lttpr_mode == LTTPR_MODE_TRANSPARENT) {
+               link->apply_vendor_specific_lttpr_link_rate_wa = true;
                vendor_specific_lttpr_wa_four(link, true);
-       else
+       } else {
                dpcd_exit_training_mode(link);
+       }
 
        /* configure link prior to entering training mode */
        dpcd_configure_lttpr_mode(link, &lt_settings);
@@ -2409,10 +2413,12 @@ enum link_training_result 
dc_link_dp_perform_link_training(
        /* exit training mode */
        if (link->dc->debug.apply_vendor_specific_lttpr_wa &&
                        (link->chip_caps & 
EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN) &&
-                       link->lttpr_mode == LTTPR_MODE_TRANSPARENT)
+                       link->lttpr_mode == LTTPR_MODE_TRANSPARENT) {
+               link->apply_vendor_specific_lttpr_link_rate_wa = false;
                vendor_specific_lttpr_wa_four(link, (status != 
LINK_TRAINING_SUCCESS));
-       else
+       } else {
                dpcd_exit_training_mode(link);
+       }
 
        /* switch to video idle */
        if ((status == LINK_TRAINING_SUCCESS) || !skip_video_pattern)
diff --git a/drivers/gpu/drm/amd/display/dc/dc_link.h 
b/drivers/gpu/drm/amd/display/dc/dc_link.h
index a99950883e85..c0ee625aa357 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_link.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_link.h
@@ -188,6 +188,7 @@ struct dc_link {
 
        /* Vendor specific LTTPR workaround variables */
        uint8_t vendor_specific_lttpr_link_rate_wa;
+       bool apply_vendor_specific_lttpr_link_rate_wa;
 
        /* MST record stream using this link */
        struct link_flags {
-- 
2.25.1