On 4/10/25 12:21 PM, Maxime Ripard wrote:
> Hi,
>
> On Wed, Mar 26, 2025 at 12:20:04PM +0200, Cristian Ciocaltea wrote:
>> Provide test to verify a forced fallback to YUV420 output cannot succeed
>> when driver doesn't advertise YUV420 support.
>>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocal...@collabora.com>
>> ---
>> drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c | 46
>> ++++++++++++++++++++++
>> 1 file changed, 46 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
>> 99bedb2d6f555b3b140256000dfa7491d2a8f515..c2976b42aa2aacd2a68a871bffe97e795ca713d4
>> 100644
>> --- a/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
>> +++ b/drivers/gpu/drm/tests/drm_hdmi_state_helper_test.c
>> @@ -1493,6 +1493,51 @@ static void
>> drm_test_check_max_tmds_rate_format_fallback_yuv420(struct kunit *te
>> drm_modeset_acquire_fini(&ctx);
>> }
>>
>> +/*
>> + * Test that if a driver supports only RGB, but the chosen mode can be
>> + * supported by the screen only in YUV420 output format, we end up with
>> + * an unsuccessful forced fallback attempt.
>
> What do you mean by "forced"?
I wanted to describe the context where there's no alternative other than
doing the fallback. Should we replace with "mandatory" maybe?
>> + */
>> +static void drm_test_check_driver_unsupported_fallback_yuv420(struct kunit
>> *test)
>> +{
>> + struct drm_atomic_helper_connector_hdmi_priv *priv;
>> + struct drm_modeset_acquire_ctx ctx;
>> + struct drm_display_info *info;
>> + struct drm_display_mode *yuv420_only_mode;
>> + struct drm_connector *conn;
>> + struct drm_device *drm;
>> + struct drm_crtc *crtc;
>> + int ret;
>> +
>> + priv = drm_kunit_helper_connector_hdmi_init_with_edid(test,
>> + BIT(HDMI_COLORSPACE_RGB),
>> + 12,
>> +
>> test_edid_hdmi_1080p_rgb_yuv_4k_yuv420_dc_max_200mhz);
>> + 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_FALSE(test, conn->ycbcr_420_allowed);
>> +
>> + yuv420_only_mode = drm_kunit_display_mode_from_cea_vic(test, drm, 95);
>> + KUNIT_ASSERT_NOT_NULL(test, yuv420_only_mode);
>> + KUNIT_ASSERT_TRUE(test, drm_mode_is_420_only(info, yuv420_only_mode));
>> +
>> + drm_modeset_acquire_init(&ctx, 0);
>> +
>> + ret = drm_kunit_helper_enable_crtc_connector(test, drm,
>> + crtc, conn,
>> + yuv420_only_mode,
>> + &ctx);
>> + KUNIT_EXPECT_LT(test, ret, 0);
>
> I think that's where your current approach falls a bit short. You should
> really craft the state yourself and check the returned value of
> drm_atomic_check_only(), not rely on
> drm_kunit_helper_enable_crtc_connector() doing the right thing, when it
> doesn't really tell you :)
Ack.
>
>> + drm_modeset_drop_locks(&ctx);
>> + drm_modeset_acquire_fini(&ctx);
>> +}
>> +
>
> We still need to do the same with a driver that supports both, but the
> monitor doesn't.
Ack.
Thanks,
Cristian
