drm/amd/display: initialize get_max_link_cap

[why]
usb3->usb2 switch system hang.
driver needs to limit the max sink cap based on DP4 mode.

[how]
based on s_dpalt check and DP4 check:
limit the USB-C DPALT DP maximum supported lane count.

Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Reviewed-by: Chris Park <Chris.Park@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_link_encoder.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_link_encoder.c
index e4ac730..15d513b 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_link_encoder.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_link_encoder.c
@@ -311,6 +311,28 @@ void enc2_hw_init(struct link_encoder *enc)
        dcn10_aux_initialize(enc10);
 }
 
+void dcn20_link_encoder_get_max_link_cap(struct link_encoder *enc,
+       struct dc_link_settings *link_settings)
+{
+       struct dcn10_link_encoder *enc10 = TO_DCN10_LINK_ENC(enc);
+       uint32_t value;
+
+       REG_GET(RDPCSTX_PHY_CNTL6, RDPCS_PHY_DPALT_DP4, &value);
+
+       if (!value && link_settings->lane_count > LANE_COUNT_TWO)
+               link_settings->lane_count = LANE_COUNT_TWO;
+}
+bool dcn20_link_encoder_is_in_alt_mode(struct link_encoder *enc)
+{
+       struct dcn10_link_encoder *enc10 = TO_DCN10_LINK_ENC(enc);
+       uint32_t value;
+
+       REG_GET(RDPCSTX_PHY_CNTL6, RDPCS_PHY_DPALT_DISABLE, &value);
+
+       // if value == 1 alt mode is disabled, otherwise it is enabled
+       return !value;
+}
+
 static const struct link_encoder_funcs dcn20_link_enc_funcs = {
        .read_state = link_enc2_read_state,
        .validate_output_with_stream =
@@ -338,6 +360,8 @@ static const struct link_encoder_funcs dcn20_link_enc_funcs = {
        .fec_is_active = enc2_fec_is_active,
        .get_dig_mode = dcn10_get_dig_mode,
        .get_dig_frontend = dcn10_get_dig_frontend,
+       .is_in_alt_mode = dcn20_link_encoder_is_in_alt_mode,
+       .get_max_link_cap = dcn20_link_encoder_get_max_link_cap,
 };
 
 void dcn20_link_encoder_construct(