[PATCH 09/23] drm/amd/display: Determine early if a link has supported encoders (v2)

["Timur Kristóf" <timur.kristof@gmail.com>]

Avoid initializing DDC, HPD, etc. when we know that the link is
not going to be constructed because it has no supported encoders.

This is mainly useful for old GPUs which may have encoders such
as TRAVIS and NUTMEG that are not yet supported by DC.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
---
 .../drm/amd/display/dc/link/link_factory.c    | 23 +++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/link/link_factory.c b/drivers/gpu/drm/amd/display/dc/link/link_factory.c
index 31a73867cd4c..dd636a994bd6 100644
--- a/drivers/gpu/drm/amd/display/dc/link/link_factory.c
+++ b/drivers/gpu/drm/amd/display/dc/link/link_factory.c
@@ -451,6 +451,14 @@ static enum channel_id get_ddc_line(struct dc_link *link)
 	return channel;
 }
 
+static bool transmitter_supported(const enum transmitter transmitter)
+{
+	return transmitter != TRANSMITTER_UNKNOWN &&
+		transmitter != TRANSMITTER_NUTMEG_CRT &&
+		transmitter != TRANSMITTER_TRAVIS_CRT &&
+		transmitter != TRANSMITTER_TRAVIS_LCD;
+}
+
 static bool construct_phy(struct dc_link *link,
 			      const struct link_init_data *init_params)
 {
@@ -482,6 +490,17 @@ static bool construct_phy(struct dc_link *link,
 	link->link_id =
 		bios->funcs->get_connector_id(bios, init_params->connector_index);
 
+	/* Determine early if the link has any supported encoders,
+	 * so that we avoid initializing DDC and HPD, etc.
+	 */
+	bp_funcs->get_src_obj(bios, link->link_id, 0, &enc_init_data.encoder);
+	enc_init_data.transmitter = translate_encoder_to_transmitter(enc_init_data.encoder);
+
+	if (!transmitter_supported(enc_init_data.transmitter)) {
+		DC_LOG_WARNING("link_id %d has unsupported encoder\n", link->link_id.id);
+		return false;
+	}
+
 	link->ep_type = DISPLAY_ENDPOINT_PHY;
 
 	DC_LOG_DC("BIOS object table - link_id: %d", link->link_id.id);
@@ -611,16 +630,12 @@ static bool construct_phy(struct dc_link *link,
 		dal_ddc_get_line(get_ddc_pin(link->ddc));
 
 	enc_init_data.ctx = dc_ctx;
-	bp_funcs->get_src_obj(dc_ctx->dc_bios, link->link_id, 0,
-			      &enc_init_data.encoder);
 	enc_init_data.connector = link->link_id;
 	enc_init_data.channel = get_ddc_line(link);
 	enc_init_data.hpd_source = get_hpd_line(link);
 
 	link->hpd_src = enc_init_data.hpd_source;
 
-	enc_init_data.transmitter =
-		translate_encoder_to_transmitter(enc_init_data.encoder);
 	link->link_enc =
 		link->dc->res_pool->funcs->link_enc_create(dc_ctx, &enc_init_data);
 
-- 
2.51.0