[PATCH 2/3] drm/komeda: Add drm_ctm_to_coeffs()

[james qian wang (Arm Technology China)]

This function is used to convert drm_color_ctm S31.32 sign-magnitude
value to komeda required Q2.12 2's complement

Signed-off-by: james qian wang (Arm Technology China) <james.qian.wang@xxxxxxx>
---
 .../arm/display/komeda/komeda_color_mgmt.c    | 27 +++++++++++++++++++
 .../arm/display/komeda/komeda_color_mgmt.h    |  1 +
 2 files changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c b/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c
index c180ce70c26c..c92c82eebddb 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c
@@ -117,3 +117,30 @@ void drm_lut_to_fgamma_coeffs(struct drm_property_blob *lut_blob, u32 *coeffs)
 {
 	drm_lut_to_coeffs(lut_blob, coeffs, sector_tbl, ARRAY_SIZE(sector_tbl));
 }
+
+/* Convert from S31.32 sign-magnitude to HW Q2.12 2's complement */
+static s32 drm_ctm_s31_32_to_q2_12(u64 input)
+{
+	u64 mag = (input & ~BIT_ULL(63)) >> 20;
+	bool negative = !!(input & BIT_ULL(63));
+	u32 val;
+
+	/* the range of signed 2s complement is [-2^n, 2^n - 1] */
+	val = clamp_val(mag, 0, negative ? BIT(14) : BIT(14) - 1);
+
+	return negative ? 0 - val : val;
+}
+
+void drm_ctm_to_coeffs(struct drm_property_blob *ctm_blob, u32 *coeffs)
+{
+	struct drm_color_ctm *ctm;
+	u32 i;
+
+	if (!ctm_blob)
+		return;
+
+	ctm = ctm_blob->data;
+
+	for (i = 0; i < KOMEDA_N_CTM_COEFFS; i++)
+		coeffs[i] = drm_ctm_s31_32_to_q2_12(ctm->matrix[i]);
+}
diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h b/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h
index 08ab69281648..2f4668466112 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h
@@ -18,6 +18,7 @@
 #define KOMEDA_N_CTM_COEFFS		9
 
 void drm_lut_to_fgamma_coeffs(struct drm_property_blob *lut_blob, u32 *coeffs);
+void drm_ctm_to_coeffs(struct drm_property_blob *ctm_blob, u32 *coeffs);
 
 const s32 *komeda_select_yuv2rgb_coeffs(u32 color_encoding, u32 color_range);
 
-- 
2.20.1