linux-kernel - Re: [PATCH v4 23/23] drm/tests: hdmi: Add test for unsupported RGB/YUV420 mode

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Message-ID: <20250519-classy-millipede-of-competence-4bb6ad@houat>
Date: Mon, 19 May 2025 10:42:37 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Dave Stevenson <dave.stevenson@...pberrypi.com>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, Dmitry Baryshkov <lumag@...nel.org>, kernel@...labora.com, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 23/23] drm/tests: hdmi: Add test for unsupported
 RGB/YUV420 mode

Hi,

On Fri, Apr 25, 2025 at 01:27:14PM +0300, Cristian Ciocaltea wrote:
> Provide a test to verify that if both driver and screen support RGB and
> YUV420 formats, drm_atomic_helper_connector_hdmi_check() cannot succeed
> when trying to set a mode unsupported by the display.
> 
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
>  drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c | 66 ++++++++++++++++++++++
>  1 file changed, 66 insertions(+)
> 
> 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 d79084cfb516b69c4244098c0767d604ad02f2c3..6337a1c52b86810c638f446c4995e7ee63dbc084 100644
> --- a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
> +++ b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
> @@ -1622,6 +1622,71 @@ static void drm_test_check_driver_unsupported_fallback_yuv420(struct kunit *test
>  	drm_modeset_acquire_fini(&ctx);
>  }
>  
> +/*
> + * Test that if a driver and screen supports RGB and YUV420 formats, but the
> + * chosen mode cannot be supported by the screen, we end up with unsuccessful
> + * fallback attempts.
> + */
> +static void drm_test_check_display_unsupported_fallback_rgb_yuv420(struct kunit *test)
> +{
> +	struct drm_atomic_helper_connector_hdmi_priv *priv;
> +	struct drm_modeset_acquire_ctx ctx;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_atomic_state *state;
> +	struct drm_display_info *info;
> +	struct drm_display_mode *preferred, *unsupported_mode;
> +	struct drm_connector *conn;
> +	struct drm_device *drm;
> +	struct drm_crtc *crtc;
> +	int ret;
> +
> +	priv = drm_kunit_helper_connector_hdmi_init_with_edid_funcs(test,
> +				BIT(HDMI_COLORSPACE_RGB) |
> +				BIT(HDMI_COLORSPACE_YUV420),
> +				10,
> +				&dummy_connector_hdmi_funcs,
> +				test_edid_hdmi_4k_rgb_yuv420_dc_max_340mhz);
> +	KUNIT_ASSERT_NOT_NULL(test, priv);
> +
> +	drm = &priv->drm;
> +	crtc = priv->crtc;
> +	conn = &priv->connector;
> +	info = &conn->display_info;
> +	KUNIT_ASSERT_TRUE(test, info->is_hdmi);
> +	KUNIT_ASSERT_TRUE(test, conn->ycbcr_420_allowed);
> +
> +	preferred = find_preferred_mode(conn);
> +	KUNIT_ASSERT_NOT_NULL(test, preferred);
> +
> +	unsupported_mode = drm_kunit_display_mode_from_cea_vic(test, drm, 96);
> +	KUNIT_ASSERT_NOT_NULL(test, unsupported_mode);

I'm not sure what this one is supposed to test. If the mode is
unsupported by the screen, it will be for both YUV and RGB, right? So
what are we testing here?

Maxime

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