A lot of HDMI drivers have some variation of the formula to calculate
the TMDS character rate from a mode, but few of them actually take all
parameters into account.
Let's create a helper to provide that rate taking all parameters into
account.
Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
---
drivers/gpu/drm/drm_connector.c | 59 ++++++
drivers/gpu/drm/tests/drm_connector_test.c | 323 +++++++++++++++++++++++++++++
include/drm/drm_connector.h | 5 +
3 files changed, 387 insertions(+)
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index a72f38b6dbc8..667326b09acc 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -2973,6 +2973,65 @@ void drm_connector_update_privacy_screen(const struct drm_connector_state *conne
}
EXPORT_SYMBOL(drm_connector_update_privacy_screen);
+/**
+ * drm_connector_hdmi_compute_mode_clock() - Computes the TMDS Character Rate
+ * @mode: Display mode to compute the clock for
+ * @bpc: Bits per character
+ * @fmt: Output Pixel Format used
+ *
+ * Returns the TMDS Character Rate for a given mode, bpc count and output format.
+ *
+ * RETURNS:
+ * The TMDS Character Rate, in Hertz, or 0 on error.
+ */
+unsigned long long
+drm_connector_hdmi_compute_mode_clock(const struct drm_display_mode *mode,
+ unsigned int bpc,
+ enum hdmi_colorspace fmt)
+{
+ unsigned long long clock = mode->clock * 1000ULL;
+ unsigned int vic = drm_match_cea_mode(mode);
+
+ /*
+ * CTA-861-G Spec, section 5.4 - Color Coding and Quantization
+ * mandates that VIC 1 always uses 8 bpc.
+ */
+ if (vic == 1 && bpc != 8)
+ return 0;
+
+ /*
+ * HDMI 2.0 Spec, section 7.1 - YCbCr 4:2:0 Pixel Encoding
+ * specifies that YUV420 encoding is only available for those
+ * VICs.
+ */
+ if (fmt == HDMI_COLORSPACE_YUV420 &&
+ !(vic == 96 || vic == 97 || vic == 101 ||
+ vic == 102 || vic == 106 || vic == 107))
+ return 0;
+
+ /*
+ * HDMI 1.4b Spec, section 6.2.3 - Pixel Encoding Requirements
+ * specifies that YUV422 is 36-bit only.
+ */
+ if (fmt == HDMI_COLORSPACE_YUV422 && bpc != 12)
+ return 0;
+
+ if (fmt == HDMI_COLORSPACE_YUV420)
+ clock = clock / 2;
+
+ if (mode->flags & DRM_MODE_FLAG_DBLCLK)
+ clock = clock * 2;
+
+ if (fmt == HDMI_COLORSPACE_YUV422)
+ bpc = 8;
+
+ clock = clock * bpc;
+ do_div(clock, 8);
+
+ return clock;
+}
+EXPORT_SYMBOL(drm_connector_hdmi_compute_mode_clock);
+
int drm_connector_set_obj_prop(struct drm_mode_object *obj,
struct drm_property *property,
uint64_t value)
diff --git a/drivers/gpu/drm/tests/drm_connector_test.c b/drivers/gpu/drm/tests/drm_connector_test.c
index fa6fe8084107..0a838924a546 100644
--- a/drivers/gpu/drm/tests/drm_connector_test.c
+++ b/drivers/gpu/drm/tests/drm_connector_test.c
@@ -8,7 +8,9 @@
#include <drm/drm_atomic_state_helper.h>
#include <drm/drm_connector.h>
#include <drm/drm_drv.h>
+#include <drm/drm_edid.h>
#include <drm/drm_kunit_helpers.h>
+#include <drm/drm_modes.h>
#include <kunit/test.h>
@@ -719,10 +721,331 @@ static struct kunit_suite drm_connector_attach_broadcast_rgb_property_test_suite
.test_cases = drm_connector_attach_broadcast_rgb_property_tests,
};
+/*
+ * Test that for a given mode, with 8bpc and an RGB output the TMDS
+ * character rate is equal to the mode pixel clock.
+ */
+static void drm_test_drm_connector_hdmi_compute_mode_clock_rgb(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ unsigned long long rate;
+ struct drm_device *drm = &priv->drm;
+
+ mode = drm_display_mode_from_cea_vic(drm, 16);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_RGB);
+ KUNIT_ASSERT_GT(test, rate, 0);
+ KUNIT_EXPECT_EQ(test, mode->clock * 1000ULL, rate);
+}
+
+/*
+ * Test that for a given mode, with 10bpc and an RGB output the TMDS
+ * character rate is equal to 1.25 times the mode pixel clock.
+ */
+static void drm_test_drm_connector_hdmi_compute_mode_clock_rgb_10bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ unsigned long long rate;
+ struct drm_device *drm = &priv->drm;
+
+ mode = drm_display_mode_from_cea_vic(drm, 16);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 10, HDMI_COLORSPACE_RGB);
+ KUNIT_ASSERT_GT(test, rate, 0);
+ KUNIT_EXPECT_EQ(test, mode->clock * 1250, rate);
+}
+
+/*
+ * Test that for the VIC-1 mode, with 10bpc and an RGB output the TMDS
+ * character rate computation fails.
+ */
+static void drm_test_drm_connector_hdmi_compute_mode_clock_rgb_10bpc_vic_1(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ unsigned long long rate;
+ struct drm_device *drm = &priv->drm;
+
+ mode = drm_display_mode_from_cea_vic(drm, 1);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 10, HDMI_COLORSPACE_RGB);
+ KUNIT_EXPECT_EQ(test, rate, 0);
+}
+
+/*
+ * Test that for a given mode, with 12bpc and an RGB output the TMDS
+ * character rate is equal to 1.5 times the mode pixel clock.
+ */
+static void drm_test_drm_connector_hdmi_compute_mode_clock_rgb_12bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ unsigned long long rate;
+ struct drm_device *drm = &priv->drm;
+
+ mode = drm_display_mode_from_cea_vic(drm, 16);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 12, HDMI_COLORSPACE_RGB);
+ KUNIT_ASSERT_GT(test, rate, 0);
+ KUNIT_EXPECT_EQ(test, mode->clock * 1500, rate);
+}
+
+/*
+ * Test that for the VIC-1 mode, with 12bpc and an RGB output the TMDS
+ * character rate computation fails.
+ */
+static void drm_test_drm_connector_hdmi_compute_mode_clock_rgb_12bpc_vic_1(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ unsigned long long rate;
+ struct drm_device *drm = &priv->drm;
+
+ mode = drm_display_mode_from_cea_vic(drm, 1);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 12, HDMI_COLORSPACE_RGB);
+ KUNIT_EXPECT_EQ(test, rate, 0);
+}
+
+/*
+ * Test that for a mode with the pixel repetition flag, the TMDS
+ * character rate is indeed double the mode pixel clock.
+ */
+static void drm_test_drm_connector_hdmi_compute_mode_clock_rgb_double(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ unsigned long long rate;
+ struct drm_device *drm = &priv->drm;
+
+ mode = drm_display_mode_from_cea_vic(drm, 6);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_TRUE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_RGB);
+ KUNIT_ASSERT_GT(test, rate, 0);
+ KUNIT_EXPECT_EQ(test, (mode->clock * 1000ULL) * 2, rate);
+}
+
+/*
+ * Test that the TMDS character rate computation for the VIC modes
+ * explicitly listed in the spec as supporting YUV420 succeed and return
+ * half the mode pixel clock.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv420_valid(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned long long rate;
+ unsigned int vic = *(unsigned int *)test->param_value;
+
+ mode = drm_display_mode_from_cea_vic(drm, vic);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_YUV420);
+ KUNIT_ASSERT_GT(test, rate, 0);
+ KUNIT_EXPECT_EQ(test, (mode->clock * 1000ULL) / 2, rate);
+}
+
+static const unsigned int drm_connector_hdmi_compute_mode_clock_yuv420_vic_valid_tests[] = {
+ 96, 97, 101, 102, 106, 107,
+};
+
+static void drm_connector_hdmi_compute_mode_clock_yuv420_vic_desc(const unsigned int *vic, char *desc)
+{
+ sprintf(desc, "VIC %u", *vic);
+}
+
+KUNIT_ARRAY_PARAM(drm_connector_hdmi_compute_mode_clock_yuv420_valid,
+ drm_connector_hdmi_compute_mode_clock_yuv420_vic_valid_tests,
+ drm_connector_hdmi_compute_mode_clock_yuv420_vic_desc);
+
+/*
+ * Test that trying to compute the TMDS char rate with the YUV420 format
+ * for a mode that doesn't support the YUV420 encoding returns an error.
+ *
+ * TODO: We should probably test this with all the VIC but the
+ * explicitly supported ones. Since the list of VIC is quite long and
+ * not linear, the best way to support it at the moment would be to
+ * create a custom gen_params function that would only return valid
+ * VICs. At the moment, that function expects to get a pointer back
+ * however, and compilers don't really like casting between integer and
+ * pointers.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv420_invalid(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned long long rate;
+
+ mode = drm_display_mode_from_cea_vic(drm, 42);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_YUV420);
+ KUNIT_EXPECT_EQ(test, rate, 0);
+}
+
+/*
+ * Test that for a given mode listed supporting it and an YUV420 output
+ * with 10bpc, the TMDS character rate is equal to 0.625 times the mode
+ * pixel clock.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv420_10_bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned int vic =
+ drm_connector_hdmi_compute_mode_clock_yuv420_vic_valid_tests[0];
+ unsigned long long rate;
+
+ mode = drm_display_mode_from_cea_vic(drm, vic);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 10, HDMI_COLORSPACE_YUV420);
+ KUNIT_ASSERT_GT(test, rate, 0);
+
+ KUNIT_EXPECT_EQ(test, mode->clock * 625, rate);
+}
+
+/*
+ * Test that for a given mode listed supporting it and an YUV420 output
+ * with 12bpc, the TMDS character rate is equal to 0.75 times the mode
+ * pixel clock.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv420_12_bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned int vic =
+ drm_connector_hdmi_compute_mode_clock_yuv420_vic_valid_tests[0];
+ unsigned long long rate;
+
+ mode = drm_display_mode_from_cea_vic(drm, vic);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 12, HDMI_COLORSPACE_YUV420);
+ KUNIT_ASSERT_GT(test, rate, 0);
+
+ KUNIT_EXPECT_EQ(test, mode->clock * 750, rate);
+}
+
+/*
+ * Test that for a given mode, the computation of the TMDS character
+ * rate with 8bpc and a YUV422 output fails.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv422_8_bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned long long rate;
+
+ mode = drm_display_mode_from_cea_vic(drm, 16);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_YUV422);
+ KUNIT_EXPECT_EQ(test, rate, 0);
+}
+
+/*
+ * Test that for a given mode, the computation of the TMDS character
+ * rate with 10bpc and a YUV422 output fails.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv422_10_bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned long long rate;
+
+ mode = drm_display_mode_from_cea_vic(drm, 16);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 10, HDMI_COLORSPACE_YUV422);
+ KUNIT_EXPECT_EQ(test, rate, 0);
+}
+
+/*
+ * Test that for a given mode, the computation of the TMDS character
+ * rate with 12bpc and a YUV422 output succeeds and returns a rate equal
+ * to the mode pixel clock.
+ */
+static void drm_test_connector_hdmi_compute_mode_clock_yuv422_12_bpc(struct kunit *test)
+{
+ struct drm_connector_init_priv *priv = test->priv;
+ const struct drm_display_mode *mode;
+ struct drm_device *drm = &priv->drm;
+ unsigned long long rate;
+
+ mode = drm_display_mode_from_cea_vic(drm, 16);
+ KUNIT_ASSERT_NOT_NULL(test, mode);
+
+ KUNIT_ASSERT_FALSE(test, mode->flags & DRM_MODE_FLAG_DBLCLK);
+
+ rate = drm_connector_hdmi_compute_mode_clock(mode, 12, HDMI_COLORSPACE_YUV422);
+ KUNIT_ASSERT_GT(test, rate, 0);
+ KUNIT_EXPECT_EQ(test, mode->clock * 1000, rate);
+}
+
+static struct kunit_case drm_connector_hdmi_compute_mode_clock_tests[] = {
+ KUNIT_CASE(drm_test_drm_connector_hdmi_compute_mode_clock_rgb),
+ KUNIT_CASE(drm_test_drm_connector_hdmi_compute_mode_clock_rgb_10bpc),
+ KUNIT_CASE(drm_test_drm_connector_hdmi_compute_mode_clock_rgb_10bpc_vic_1),
+ KUNIT_CASE(drm_test_drm_connector_hdmi_compute_mode_clock_rgb_12bpc),
+ KUNIT_CASE(drm_test_drm_connector_hdmi_compute_mode_clock_rgb_12bpc_vic_1),
+ KUNIT_CASE(drm_test_drm_connector_hdmi_compute_mode_clock_rgb_double),
+ KUNIT_CASE_PARAM(drm_test_connector_hdmi_compute_mode_clock_yuv420_valid,
+ drm_connector_hdmi_compute_mode_clock_yuv420_valid_gen_params),
+ KUNIT_CASE(drm_test_connector_hdmi_compute_mode_clock_yuv420_invalid),
+ KUNIT_CASE(drm_test_connector_hdmi_compute_mode_clock_yuv420_10_bpc),
+ KUNIT_CASE(drm_test_connector_hdmi_compute_mode_clock_yuv420_12_bpc),
+ KUNIT_CASE(drm_test_connector_hdmi_compute_mode_clock_yuv422_8_bpc),
+ KUNIT_CASE(drm_test_connector_hdmi_compute_mode_clock_yuv422_10_bpc),
+ KUNIT_CASE(drm_test_connector_hdmi_compute_mode_clock_yuv422_12_bpc),
+ { }
+};
+
+static struct kunit_suite drm_connector_hdmi_compute_mode_clock_test_suite = {
+ .name = "drm_test_connector_hdmi_compute_mode_clock",
+ .init = drm_test_connector_init,
+ .test_cases = drm_connector_hdmi_compute_mode_clock_tests,
+};
+
kunit_test_suites(
&drmm_connector_hdmi_init_test_suite,
&drmm_connector_init_test_suite,
&drm_connector_attach_broadcast_rgb_property_test_suite,
+ &drm_connector_hdmi_compute_mode_clock_test_suite,
&drm_get_tv_mode_from_name_test_suite,
&drm_hdmi_connector_get_broadcast_rgb_name_test_suite,
&drm_hdmi_connector_get_output_format_name_test_suite
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 74db5ce47e01..0cc5a8732664 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -38,6 +38,7 @@ struct drm_connector_helper_funcs;
struct drm_modeset_acquire_ctx;
struct drm_device;
struct drm_crtc;
+struct drm_display_mode;
struct drm_encoder;
struct drm_panel;
struct drm_property;
@@ -2136,6 +2137,10 @@ void drm_connector_attach_privacy_screen_properties(struct drm_connector *conn);
void drm_connector_attach_privacy_screen_provider(
struct drm_connector *connector, struct drm_privacy_screen *priv);
void drm_connector_update_privacy_screen(const struct drm_connector_state *connector_state);
+unsigned long long
+drm_connector_hdmi_compute_mode_clock(const struct drm_display_mode *mode,
+ unsigned int bpc,
+ enum hdmi_colorspace fmt);
/**
* struct drm_tile_group - Tile group metadata
--
2.43.0
