drm/amd/display: add plane HDR multiplier driver-specific property

Multiplier to 'gain' the plane. When PQ is decoded using the fixed func
transfer function to the internal FP16 fb, 1.0 -> 80 nits (on AMD at
least) When sRGB is decoded, 1.0 -> 1.0.  Therefore, 1.0 multiplier = 80
nits for SDR content. So if you want, 203 nits for SDR content, pass in
(203.0 / 80.0).

v4:
- comment about the PQ TF need for L-to-NL (from Harry's review)

Reviewed-by: Harry Wentland <[email protected]>
Signed-off-by: Joshua Ashton <[email protected]>
Co-developed-by: Melissa Wen <[email protected]>
Signed-off-by: Melissa Wen <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index baa73a6f47a9..d36d68d517a8 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -55,6 +55,9 @@
 #define HDMI_AMD_VENDOR_SPECIFIC_DATA_BLOCK_IEEE_REGISTRATION_ID 0x00001A
 #define AMD_VSDB_VERSION_3_FEATURECAP_REPLAYMODE 0x40
 #define HDMI_AMD_VENDOR_SPECIFIC_DATA_BLOCK_VERSION_3 0x3
+
+#define AMDGPU_HDR_MULT_DEFAULT (0x100000000LL)
+
 /*
 #include "include/amdgpu_dal_power_if.h"
 #include "amdgpu_dm_irq.h"
@@ -767,6 +770,20 @@ struct dm_plane_state {
 	 * linearize.
 	 */
 	enum amdgpu_transfer_function degamma_tf;
+	/**
+	 * @hdr_mult:
+	 *
+	 * Multiplier to 'gain' the plane.  When PQ is decoded using the fixed
+	 * func transfer function to the internal FP16 fb, 1.0 -> 80 nits (on
+	 * AMD at least). When sRGB is decoded, 1.0 -> 1.0, obviously.
+	 * Therefore, 1.0 multiplier = 80 nits for SDR content.  So if you
+	 * want, 203 nits for SDR content, pass in (203.0 / 80.0).  Format is
+	 * S31.32 sign-magnitude.
+	 *
+	 * HDR multiplier can wide range beyond [0.0, 1.0]. This means that PQ
+	 * TF is needed for any subsequent linear-to-non-linear transforms.
+	 */
+	__u64 hdr_mult;
 };
 
 struct dm_crtc_state {