Re: [PATCH v3 1/7] drm/display: hdmi: add generic mode_valid helper

[Maxime Ripard <mripard@kernel.org>]

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Hi,

On Sat, Nov 09, 2024 at 02:35:05PM +0200, Dmitry Baryshkov wrote:
> Add drm_hdmi_connector_mode_valid(), generic helper for HDMI connectors.
> It can be either used directly or as a part of the .mode_valid callback.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  drivers/gpu/drm/display/drm_hdmi_state_helper.c    |  21 +++
>  drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c | 181 ++++++++++++++++++++-
>  include/drm/display/drm_hdmi_state_helper.h        |   4 +
>  3 files changed, 204 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> index feb7a3a759811aed70c679be8704072093e2a79b..80bf2829ba89b5f84fed4fa9eb1d6302e10a4f9e 100644
> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> @@ -521,6 +521,27 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector,
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_check);
>  
> +/**
> + * drm_hdmi_connector_mode_valid() - Check if mode is valid for HDMI connector
> + * @connector: DRM connector to validate the mode
> + * @mode: Display mode to validate
> + *
> + * Generic .mode_valid implementation for HDMI connectors.
> + */
> +enum drm_mode_status
> +drm_hdmi_connector_mode_valid(struct drm_connector *connector,
> +			      struct drm_display_mode *mode)
> +{
> +	unsigned long long clock;
> +
> +	clock = drm_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_RGB);
> +	if (!clock)
> +		return MODE_ERROR;
> +
> +	return hdmi_clock_valid(connector, mode, clock);
> +}
> +EXPORT_SYMBOL(drm_hdmi_connector_mode_valid);
> +
>  static int clear_device_infoframe(struct drm_connector *connector,
>  				  enum hdmi_infoframe_type type)
>  {
> 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 294773342e710dc56772f839c2db9c2e487bbc1e..67c3e882592b00d803d8cba5d183aa90339a16b4 100644
> --- a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
> +++ b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
> @@ -43,10 +43,14 @@ struct drm_atomic_helper_connector_hdmi_priv {
>  static struct drm_display_mode *find_preferred_mode(struct drm_connector *connector)
>  {
>  	struct drm_device *drm = connector->dev;
> -	struct drm_display_mode *mode, *preferred;
> +	struct drm_display_mode *mode, *preferred = NULL;
>  
>  	mutex_lock(&drm->mode_config.mutex);
> -	preferred = list_first_entry(&connector->modes, struct drm_display_mode, head);
> +
> +	/* Handle the case when all modes were rejected by mode_valid() */
> +	if (!list_empty(&connector->modes))
> +		preferred = list_first_entry(&connector->modes, struct drm_display_mode, head);
> +

Sorry if it wasn't clear in my previous review, but I would have
expected a separate patch for that change.

>  	list_for_each_entry(mode, &connector->modes, head)
>  		if (mode->type & DRM_MODE_TYPE_PREFERRED)
>  			preferred = mode;
> @@ -125,6 +129,18 @@ static const struct drm_connector_hdmi_funcs reject_connector_hdmi_funcs = {
>  	.tmds_char_rate_valid	= reject_connector_tmds_char_rate_valid,
>  };
>  
> +static enum drm_mode_status
> +reject_100MHz_connector_tmds_char_rate_valid(const struct drm_connector *connector,
> +					     const struct drm_display_mode *mode,
> +					     unsigned long long tmds_rate)
> +{
> +	return (tmds_rate > 100ULL * 1000 * 1000) ? MODE_BAD : MODE_OK;
> +}
> +
> +static const struct drm_connector_hdmi_funcs reject_100_MHz_connector_hdmi_funcs = {
> +	.tmds_char_rate_valid	= reject_100MHz_connector_tmds_char_rate_valid,
> +};
> +
>  static int dummy_connector_get_modes(struct drm_connector *connector)
>  {
>  	struct drm_atomic_helper_connector_hdmi_priv *priv =
> @@ -147,6 +163,33 @@ static int dummy_connector_get_modes(struct drm_connector *connector)
>  static const struct drm_connector_helper_funcs dummy_connector_helper_funcs = {
>  	.atomic_check	= drm_atomic_helper_connector_hdmi_check,
>  	.get_modes	= dummy_connector_get_modes,
> +	.mode_valid	= drm_hdmi_connector_mode_valid,
> +};
> +
> +static int dummy_connector_get_modes_100MHz_max_clock(struct drm_connector *connector)
> +{
> +	struct drm_atomic_helper_connector_hdmi_priv *priv =
> +		connector_to_priv(connector);
> +	const struct drm_edid *edid;
> +	unsigned int num_modes;
> +
> +	edid = drm_edid_alloc(priv->current_edid, priv->current_edid_len);
> +	if (!edid)
> +		return -EINVAL;
> +
> +	drm_edid_connector_update(connector, edid);
> +	connector->display_info.max_tmds_clock = 100 * 1000;
> +	num_modes = drm_edid_connector_add_modes(connector);
> +
> +	drm_edid_free(edid);
> +
> +	return num_modes;
> +}

I'd rather create a new fake edid than mess with those fields directly.

> +static const struct drm_connector_helper_funcs dummy_connector_helper_funcs_max_tmds_clock = {
> +	.atomic_check	= drm_atomic_helper_connector_hdmi_check,
> +	.get_modes	= dummy_connector_get_modes_100MHz_max_clock,
> +	.mode_valid	= drm_hdmi_connector_mode_valid,
>  };
>  
>  static void dummy_hdmi_connector_reset(struct drm_connector *connector)
> @@ -1734,9 +1777,143 @@ static struct kunit_suite drm_atomic_helper_connector_hdmi_reset_test_suite = {
>  	.test_cases	= drm_atomic_helper_connector_hdmi_reset_tests,
>  };
>  
> +static void drm_test_check_mode_valid(struct kunit *test)
> +{
> +	struct drm_atomic_helper_connector_hdmi_priv *priv;
> +	struct drm_connector *conn;
> +	struct drm_display_mode *preferred;
> +
> +	priv = drm_atomic_helper_connector_hdmi_init(test,
> +						     BIT(HDMI_COLORSPACE_RGB),
> +						     8);
> +	KUNIT_ASSERT_NOT_NULL(test, priv);
> +
> +	conn = &priv->connector;
> +	preferred = find_preferred_mode(conn);
> +	KUNIT_ASSERT_NOT_NULL(test, preferred);
> +
> +	KUNIT_EXPECT_EQ(test, preferred->hdisplay, 1920);
> +	KUNIT_EXPECT_EQ(test, preferred->vdisplay, 1080);
> +	KUNIT_EXPECT_EQ(test, preferred->clock, 148500);
> +}

We need a comment on what that test tests, and expects.

> +/*
> + * Verify that tmds_char_rate_valid() can reject all modes.
> + */
> +static void drm_test_check_mode_valid_reject(struct kunit *test)
> +{
> +	struct drm_atomic_helper_connector_hdmi_priv *priv;
> +	struct drm_connector *conn;
> +	struct drm_display_mode *preferred;
> +	struct drm_device *drm;
> +	int ret;
> +
> +	priv = drm_atomic_helper_connector_hdmi_init(test,
> +						     BIT(HDMI_COLORSPACE_RGB),
> +						     8);
> +	KUNIT_ASSERT_NOT_NULL(test, priv);
> +
> +	conn = &priv->connector;
> +
> +	/* You shouldn't be doing that at home. */
> +	conn->hdmi.funcs = &reject_connector_hdmi_funcs;

Just make drm_atomic_helper_connector_hdmi_init take an extra pointer.
(Also, that's a super bad name, drm_kunit_helper_connector_hdmi_init or
something would probably be better)

> +	priv->current_edid = test_edid_hdmi_1080p_rgb_max_200mhz;
> +	priv->current_edid_len = ARRAY_SIZE(test_edid_hdmi_1080p_rgb_max_200mhz);
> +
> +	drm = &priv->drm;
> +
> +	mutex_lock(&drm->mode_config.mutex);
> +	ret = conn->funcs->fill_modes(conn, 4096, 4096);
> +	mutex_unlock(&drm->mode_config.mutex);
> +	KUNIT_ASSERT_EQ(test, ret, 0);
> +
> +	preferred = find_preferred_mode(conn);
> +	KUNIT_ASSERT_NULL(test, preferred);
> +}

Ditto, I can't really say what this test is doing. That's true for all the tests.

Maxime

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