[PATCH v13 15/28] drm/connector: hdmi: Compute bpc and format automatically

Maxime Ripard
2024-05-07T14:31:25Z

Now that we have all the infrastructure needed, we can add some code
that will, for a given connector state and mode, compute the best output
format and bpc.

The algorithm is equivalent to the one already found in i915 and vc4.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
drivers/gpu/drm/display/drm_hdmi_state_helper.c | 199 ++++++++++++++++++++-
drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c | 25 ++-
2 files changed, 212 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index 063421835dba..f20dcfecb6b8 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -1,9 +1,11 @@
// SPDX-License-Identifier: MIT

#include <drm/drm_atomic.h>
#include <drm/drm_connector.h>
+#include <drm/drm_edid.h>
+#include <drm/drm_print.h>

#include <drm/display/drm_hdmi_helper.h>
#include <drm/display/drm_hdmi_state_helper.h>

/**
@@ -46,10 +48,112 @@ connector_state_get_mode(const struct drm_connector_state *conn_state)
return NULL;

return &crtc_state->mode;
}

+static bool
+sink_supports_format_bpc(const struct drm_connector *connector,
+ const struct drm_display_info *info,
+ const struct drm_display_mode *mode,
+ unsigned int format, unsigned int bpc)
+{
+ struct drm_device *dev = connector->dev;
+ u8 vic = drm_match_cea_mode(mode);
+
+ /*
+ * CTA-861-F, section 5.4 - Color Coding & Quantization states
+ * that the bpc must be 8, 10, 12 or 16 except for the default
+ * 640x480 VIC1 where the value must be 8.
+ *
+ * The definition of default here is ambiguous but the spec
+ * refers to VIC1 being the default timing in several occasions
+ * so our understanding is that for the default timing (ie,
+ * VIC1), the bpc must be 8.
+ */
+ if (vic == 1 && bpc != 8) {
+ drm_dbg_kms(dev, "VIC1 requires a bpc of 8, got %u\n", bpc);
+ return false;
+ }
+
+ if (!info->is_hdmi &&
+ (format != HDMI_COLORSPACE_RGB || bpc != 8)) {
+ drm_dbg_kms(dev, "DVI Monitors require an RGB output at 8 bpc\n");
+ return false;
+ }
+
+ if (!(connector->hdmi.supported_formats & BIT(format))) {
+ drm_dbg_kms(dev, "%s format unsupported by the connector.\n",
+ drm_hdmi_connector_get_output_format_name(format));
+ return false;
+ }
+
+ switch (format) {
+ case HDMI_COLORSPACE_RGB:
+ drm_dbg_kms(dev, "RGB Format, checking the constraints.\n");
+
+ if (!(info->color_formats & DRM_COLOR_FORMAT_RGB444)) {
+ drm_dbg_kms(dev, "Sink doesn't support RGB.\n");
+ return false;
+ }
+
+ if (bpc == 10 && !(info->edid_hdmi_rgb444_dc_modes & DRM_EDID_HDMI_DC_30)) {
+ drm_dbg_kms(dev, "10 BPC but sink doesn't support Deep Color 30.\n");
+ return false;
+ }
+
+ if (bpc == 12 && !(info->edid_hdmi_rgb444_dc_modes & DRM_EDID_HDMI_DC_36)) {
+ drm_dbg_kms(dev, "12 BPC but sink doesn't support Deep Color 36.\n");
+ return false;
+ }
+
+ drm_dbg_kms(dev, "RGB format supported in that configuration.\n");
+
+ return true;
+
+ case HDMI_COLORSPACE_YUV422:
+ drm_dbg_kms(dev, "YUV422 format, checking the constraints.\n");
+
+ if (!(info->color_formats & DRM_COLOR_FORMAT_YCBCR422)) {
+ drm_dbg_kms(dev, "Sink doesn't support YUV422.\n");
+ return false;
+ }
+
+ if (bpc != 12) {
+ drm_dbg_kms(dev, "YUV422 only supports 12 bpc.\n");
+ return false;
+ }
+
+ drm_dbg_kms(dev, "YUV422 format supported in that configuration.\n");
+
+ return true;
+
+ case HDMI_COLORSPACE_YUV444:
+ drm_dbg_kms(dev, "YUV444 format, checking the constraints.\n");
+
+ if (!(info->color_formats & DRM_COLOR_FORMAT_YCBCR444)) {
+ drm_dbg_kms(dev, "Sink doesn't support YUV444.\n");
+ return false;
+ }
+
+ if (bpc == 10 && !(info->edid_hdmi_ycbcr444_dc_modes & DRM_EDID_HDMI_DC_30)) {
+ drm_dbg_kms(dev, "10 BPC but sink doesn't support Deep Color 30.\n");
+ return false;
+ }
+
+ if (bpc == 12 && !(info->edid_hdmi_ycbcr444_dc_modes & DRM_EDID_HDMI_DC_36)) {
+ drm_dbg_kms(dev, "12 BPC but sink doesn't support Deep Color 36.\n");
+ return false;
+ }
+
+ drm_dbg_kms(dev, "YUV444 format supported in that configuration.\n");
+
+ return true;
+ }
+
+ return false;
+}
+
static enum drm_mode_status
hdmi_clock_valid(const struct drm_connector *connector,
const struct drm_display_mode *mode,
unsigned long long clock)
{
@@ -90,10 +194,101 @@ hdmi_compute_clock(const struct drm_connector *connector,
conn_state->hdmi.tmds_char_rate = clock;

return 0;
}

+static bool
+hdmi_try_format_bpc(const struct drm_connector *connector,
+ struct drm_connector_state *conn_state,
+ const struct drm_display_mode *mode,
+ unsigned int bpc, enum hdmi_colorspace fmt)
+{
+ const struct drm_display_info *info = &connector->display_info;
+ struct drm_device *dev = connector->dev;
+ int ret;
+
+ drm_dbg_kms(dev, "Trying %s output format\n",
+ drm_hdmi_connector_get_output_format_name(fmt));
+
+ if (!sink_supports_format_bpc(connector, info, mode, fmt, bpc)) {
+ drm_dbg_kms(dev, "%s output format not supported with %u bpc\n",
+ drm_hdmi_connector_get_output_format_name(fmt),
+ bpc);
+ return false;
+ }
+
+ ret = hdmi_compute_clock(connector, conn_state, mode, bpc, fmt);
+ if (ret) {
+ drm_dbg_kms(dev, "Couldn't compute clock for %s output format and %u bpc\n",
+ drm_hdmi_connector_get_output_format_name(fmt),
+ bpc);
+ return false;
+ }
+
+ drm_dbg_kms(dev, "%s output format supported with %u (TMDS char rate: %llu Hz)\n",
+ drm_hdmi_connector_get_output_format_name(fmt),
+ bpc, conn_state->hdmi.tmds_char_rate);
+
+ return true;
+}
+
+static int
+hdmi_compute_format(const struct drm_connector *connector,
+ struct drm_connector_state *conn_state,
+ const struct drm_display_mode *mode,
+ unsigned int bpc)
+{
+ struct drm_device *dev = connector->dev;
+
+ /*
+ * TODO: Add support for YCbCr420 output for HDMI 2.0 capable
+ * devices, for modes that only support YCbCr420.
+ */
+ if (hdmi_try_format_bpc(connector, conn_state, mode, bpc, HDMI_COLORSPACE_RGB)) {
+ conn_state->hdmi.output_format = HDMI_COLORSPACE_RGB;
+ return 0;
+ }
+
+ drm_dbg_kms(dev, "Failed. No Format Supported for that bpc count.\n");
+
+ return -EINVAL;
+}
+
+static int
+hdmi_compute_config(const struct drm_connector *connector,
+ struct drm_connector_state *conn_state,
+ const struct drm_display_mode *mode)
+{
+ struct drm_device *dev = connector->dev;
+ unsigned int max_bpc = clamp_t(unsigned int,
+ conn_state->max_bpc,
+ 8, connector->max_bpc);
+ unsigned int bpc;
+ int ret;
+
+ for (bpc = max_bpc; bpc >= 8; bpc -= 2) {
+ drm_dbg_kms(dev, "Trying with a %d bpc output\n", bpc);
+
+ ret = hdmi_compute_format(connector, conn_state, mode, bpc);
+ if (ret)
+ continue;
+
+ conn_state->hdmi.output_bpc = bpc;
+
+ drm_dbg_kms(dev,
+ "Mode %ux%u @ %uHz: Found configuration: bpc: %u, fmt: %s, clock: %llu\n",
+ mode->hdisplay, mode->vdisplay, drm_mode_vrefresh(mode),
+ conn_state->hdmi.output_bpc,
+ drm_hdmi_connector_get_output_format_name(conn_state->hdmi.output_format),
+ conn_state->hdmi.tmds_char_rate);
+
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
/**
* drm_atomic_helper_connector_hdmi_check() - Helper to check HDMI connector atomic state
* @connector: DRM Connector
* @state: the DRM State object
*
@@ -113,13 +308,11 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector,
drm_atomic_get_new_connector_state(state, connector);
const struct drm_display_mode *mode =
connector_state_get_mode(new_conn_state);
int ret;

- ret = hdmi_compute_clock(connector, new_conn_state, mode,
- new_conn_state->hdmi.output_bpc,
- new_conn_state->hdmi.output_format);
+ ret = hdmi_compute_config(connector, new_conn_state, mode);
if (ret)
return ret;

if (old_conn_state->hdmi.output_bpc != new_conn_state->hdmi.output_bpc ||
old_conn_state->hdmi.output_format != new_conn_state->hdmi.output_format) {
diff --git a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
index ead998a691e7..a49a544d7b49 100644
--- a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
+++ b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
@@ -70,13 +70,10 @@ static int light_up_connector(struct kunit *test,
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, state);

conn_state = drm_atomic_get_connector_state(state, connector);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, conn_state);

- conn_state->hdmi.output_bpc = connector->max_bpc;
- conn_state->hdmi.output_format = HDMI_COLORSPACE_RGB;
-
ret = drm_atomic_set_crtc_for_connector(conn_state, crtc);
KUNIT_EXPECT_EQ(test, ret, 0);

crtc_state = drm_atomic_get_crtc_state(state, crtc);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, crtc_state);
@@ -251,14 +248,19 @@ static void drm_test_check_output_bpc_crtc_mode_changed(struct kunit *test)
priv = drm_atomic_helper_connector_hdmi_init(test,
BIT(HDMI_COLORSPACE_RGB),
10);
KUNIT_ASSERT_NOT_NULL(test, priv);

+ conn = &priv->connector;
+ ret = set_connector_edid(test, conn,
+ test_edid_hdmi_1080p_rgb_yuv_dc_max_200mhz,
+ ARRAY_SIZE(test_edid_hdmi_1080p_rgb_yuv_dc_max_200mhz));
+ KUNIT_ASSERT_EQ(test, ret, 0);
+
ctx = drm_kunit_helper_acquire_ctx_alloc(test);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);

- conn = &priv->connector;
preferred = find_preferred_mode(conn);
KUNIT_ASSERT_NOT_NULL(test, preferred);

drm = &priv->drm;
crtc = priv->crtc;
@@ -272,15 +274,15 @@ static void drm_test_check_output_bpc_crtc_mode_changed(struct kunit *test)
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, new_conn_state);

old_conn_state = drm_atomic_get_old_connector_state(state, conn);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, old_conn_state);

- new_conn_state->hdmi.output_bpc = 8;
+ new_conn_state->max_requested_bpc = 8;

KUNIT_ASSERT_NE(test,
- old_conn_state->hdmi.output_bpc,
- new_conn_state->hdmi.output_bpc);
+ old_conn_state->max_requested_bpc,
+ new_conn_state->max_requested_bpc);

ret = drm_atomic_check_only(state);
KUNIT_ASSERT_EQ(test, ret, 0);

old_conn_state = drm_atomic_get_old_connector_state(state, conn);
@@ -320,14 +322,19 @@ static void drm_test_check_output_bpc_crtc_mode_not_changed(struct kunit *test)
priv = drm_atomic_helper_connector_hdmi_init(test,
BIT(HDMI_COLORSPACE_RGB),
10);
KUNIT_ASSERT_NOT_NULL(test, priv);

+ conn = &priv->connector;
+ ret = set_connector_edid(test, conn,
+ test_edid_hdmi_1080p_rgb_yuv_dc_max_200mhz,
+ ARRAY_SIZE(test_edid_hdmi_1080p_rgb_yuv_dc_max_200mhz));
+ KUNIT_ASSERT_EQ(test, ret, 0);
+
ctx = drm_kunit_helper_acquire_ctx_alloc(test);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);

- conn = &priv->connector;
preferred = find_preferred_mode(conn);
KUNIT_ASSERT_NOT_NULL(test, preferred);

drm = &priv->drm;
crtc = priv->crtc;
@@ -670,11 +677,11 @@ static void drm_test_check_format_value(struct kunit *test)
8);
KUNIT_ASSERT_NOT_NULL(test, priv);

conn = &priv->connector;
conn_state = conn->state;
- KUNIT_EXPECT_EQ(test, conn_state->hdmi.output_format, HDMI_COLORSPACE_RGB);
+ KUNIT_EXPECT_EQ(test, conn_state->hdmi.output_format, 0);
}

/*
* Test that the value of the output format property out of reset is set
* to 0, and will be computed at atomic_check time.