[PATCH 29/37] drm/amd/display: Only use EETF when maxCL > max display

[sunpeng.li at amd.com]

From: Krunoslav Kovac <Krunoslav.Kovac at amd.com>

[Why&How]
BT.2390 EETF is used for tone mapping/range reduction.
Say display is 0.1 - 500 nits.
The problematic case is when content is 0-400. We apply EETF because
0<0.1 so we need to reduce the range by 0.1.

In the commit, we ignore the bottom range. Most displays map 0 to min and
then have a ramp to 0.1, so sending 0.1 is actually >0.1.
Furthermode, HW that uses 3D LUT also assumes min=0.

Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac at amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr at amd.com>
Acked-by: Leo Li <sunpeng.li at amd.com>
---
 drivers/gpu/drm/amd/display/modules/color/color_gamma.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/modules/color/color_gamma.c b/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
index 85dad356c9d5..1de4805cb8c7 100644
--- a/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
+++ b/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
@@ -959,11 +959,7 @@ static bool build_freesync_hdr(struct pwl_float_data_ex *rgb_regamma,
 	if (fs_params->max_display < 100) // cap at 100 at the top
 		max_display = dc_fixpt_from_int(100);
 
-	if (fs_params->min_content < fs_params->min_display)
-		use_eetf = true;
-	else
-		min_content = min_display;
-
+	// only max used, we don't adjust min luminance
 	if (fs_params->max_content > fs_params->max_display)
 		use_eetf = true;
 	else
-- 
2.23.0