[PATCH 2/9] drm/i915/hdmi: Restructure the sink/output format selection

Ville Syrjala
2026-03-30T23:53:55Z

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

intel_hdmi_compute_output_format() is a bit of a mess. Try to
restructure it into a more readable form.

Right now we basically have two main code paths:
- YCbCr 4:2:0 only modes
- everything else including YCbCr 4:2:0 also modes

Those two basically do the same two steps (try 4:2:0 and try 4:4:4)
but in opposite orders. Let's write that out in a more explicit
if-else form. And since I'm running out of function names I'll
rename the function with that high level logic into
intel_hdmi_compute_formats() and it will call (the new) with
intel_hdmi_compute_output_format() with an explicit sink_format
as needed.

Cc: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/i915/display/intel_hdmi.c | 112 ++++++++++++++--------
1 file changed, 70 insertions(+), 42 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index 072b0554cc24..16873fc7bcb9 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2021,6 +2021,30 @@ intel_hdmi_mode_clock_valid(struct drm_connector *_connector, int clock,
return status;
}

+static enum drm_mode_status
+intel_hdmi_sink_format_valid(struct intel_connector *connector,
+ const struct drm_display_mode *mode,
+ bool has_hdmi_sink,
+ enum intel_output_format sink_format)
+{
+ const struct drm_display_info *info = &connector->base.display_info;
+
+ switch (sink_format) {
+ case INTEL_OUTPUT_FORMAT_YCBCR420:
+ if (!has_hdmi_sink ||
+ !connector->base.ycbcr_420_allowed ||
+ !drm_mode_is_420(info, mode))
+ return MODE_NO_420;
+
+ return MODE_OK;
+ case INTEL_OUTPUT_FORMAT_RGB:
+ return MODE_OK;
+ default:
+ MISSING_CASE(sink_format);
+ return MODE_BAD;
+ }
+}
+
static enum drm_mode_status
intel_hdmi_mode_valid(struct drm_connector *_connector,
const struct drm_display_mode *mode)
@@ -2246,20 +2270,6 @@ static bool intel_hdmi_has_audio(struct intel_encoder *encoder,
return intel_conn_state->force_audio == HDMI_AUDIO_ON;
}

-static enum intel_output_format
-intel_hdmi_sink_format(const struct intel_crtc_state *crtc_state,
- struct intel_connector *connector,
- bool ycbcr_420_output)
-{
- if (!crtc_state->has_hdmi_sink)
- return INTEL_OUTPUT_FORMAT_RGB;
-
- if (connector->base.ycbcr_420_allowed && ycbcr_420_output)
- return INTEL_OUTPUT_FORMAT_YCBCR420;
- else
- return INTEL_OUTPUT_FORMAT_RGB;
-}
-
static enum intel_output_format
intel_hdmi_output_format(const struct intel_crtc_state *crtc_state)
{
@@ -2268,37 +2278,55 @@ intel_hdmi_output_format(const struct intel_crtc_state *crtc_state)

static int intel_hdmi_compute_output_format(struct intel_encoder *encoder,
struct intel_crtc_state *crtc_state,
- const struct drm_connector_state *conn_state,
- bool respect_downstream_limits)
+ struct intel_connector *connector,
+ bool respect_downstream_limits,
+ enum intel_output_format sink_format)
{
- struct intel_display *display = to_intel_display(encoder);
- struct intel_connector *connector = to_intel_connector(conn_state->connector);
const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
- const struct drm_display_info *info = &connector->base.display_info;
- bool ycbcr_420_only = drm_mode_is_420_only(info, adjusted_mode);
- int ret;

- crtc_state->sink_format =
- intel_hdmi_sink_format(crtc_state, connector, ycbcr_420_only);
-
- if (ycbcr_420_only && crtc_state->sink_format != INTEL_OUTPUT_FORMAT_YCBCR420) {
- drm_dbg_kms(display->drm,
- "YCbCr 4:2:0 mode but YCbCr 4:2:0 output not possible. Falling back to RGB.\n");
- crtc_state->sink_format = INTEL_OUTPUT_FORMAT_RGB;
- }
+ if (intel_hdmi_sink_format_valid(connector, adjusted_mode,
+ crtc_state->has_hdmi_sink, sink_format) != MODE_OK)
+ return -EINVAL;

+ crtc_state->sink_format = sink_format;
crtc_state->output_format = intel_hdmi_output_format(crtc_state);
- ret = intel_hdmi_compute_clock(encoder, crtc_state, respect_downstream_limits);
- if (ret) {
- if (crtc_state->sink_format == INTEL_OUTPUT_FORMAT_YCBCR420 ||
- !crtc_state->has_hdmi_sink ||
- !connector->base.ycbcr_420_allowed ||
- !drm_mode_is_420_also(info, adjusted_mode))
- return ret;
-
- crtc_state->sink_format = INTEL_OUTPUT_FORMAT_YCBCR420;
- crtc_state->output_format = intel_hdmi_output_format(crtc_state);
- ret = intel_hdmi_compute_clock(encoder, crtc_state, respect_downstream_limits);
+
+ return intel_hdmi_compute_clock(encoder, crtc_state, respect_downstream_limits);
+}
+
+static int intel_hdmi_compute_formats(struct intel_encoder *encoder,
+ struct intel_crtc_state *crtc_state,
+ const struct drm_connector_state *conn_state,
+ bool respect_downstream_limits)
+{
+ struct intel_display *display = to_intel_display(encoder);
+ struct intel_connector *connector = to_intel_connector(conn_state->connector);
+ const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
+ const struct drm_display_info *info = &connector->base.display_info;
+ int ret;
+
+ if (drm_mode_is_420_only(info, adjusted_mode)) {
+ ret = intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+ respect_downstream_limits,
+ INTEL_OUTPUT_FORMAT_YCBCR420);
+
+ if (ret) {
+ drm_dbg_kms(display->drm,
+ "YCbCr 4:2:0 mode but YCbCr 4:2:0 output not possible. Falling back to RGB.\n");
+
+ ret = intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+ respect_downstream_limits,
+ INTEL_OUTPUT_FORMAT_RGB);
+ }
+ } else {
+ ret = intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+ respect_downstream_limits,
+ INTEL_OUTPUT_FORMAT_RGB);
+
+ if (ret && drm_mode_is_420_also(info, adjusted_mode))
+ ret = intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+ respect_downstream_limits,
+ INTEL_OUTPUT_FORMAT_YCBCR420);
}

return ret;
@@ -2375,9 +2403,9 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
* Try to respect downstream TMDS clock limits first, if
* that fails assume the user might know something we don't.
*/
- ret = intel_hdmi_compute_output_format(encoder, pipe_config, conn_state, true);
+ ret = intel_hdmi_compute_formats(encoder, pipe_config, conn_state, true);
if (ret)
- ret = intel_hdmi_compute_output_format(encoder, pipe_config, conn_state, false);
+ ret = intel_hdmi_compute_formats(encoder, pipe_config, conn_state, false);
if (ret) {
drm_dbg_kms(display->drm,
"unsupported HDMI clock (%d kHz), rejecting mode\n",
--
2.52.0