Add a new helper function drm_color_ctm_s31_32_to_qm_n() for driver to convert S31.32 sign-magnitude to Qm.n 2's complement that supported by hardware.
V4: Address Mihai, Daniel and Ilia's review comments. V5: Includes the sign bit in the value of m (Qm.n). V6: Allows m = 0 according to Mihail's comments. V7: Address Mihail's comments. V8: Use type 'u32' to replace 'uint32_t'
Signed-off-by: james qian wang (Arm Technology China) james.qian.wang@arm.com Reviewed-by: Mihail Atanassov mihail.atanassov@arm.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_color_mgmt.c | 34 ++++++++++++++++++++++++++++++++ include/drm/drm_color_mgmt.h | 1 + 2 files changed, 35 insertions(+)
diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c index 4ce5c6d8de99..ba71e3b827f1 100644 --- a/drivers/gpu/drm/drm_color_mgmt.c +++ b/drivers/gpu/drm/drm_color_mgmt.c @@ -132,6 +132,40 @@ uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision) } EXPORT_SYMBOL(drm_color_lut_extract);
+/** + * drm_color_ctm_s31_32_to_qm_n + * + * @user_input: input value + * @m: number of integer bits, only support m <= 32, include the sign-bit + * @n: number of fractional bits, only support n <= 32 + * + * Convert and clamp S31.32 sign-magnitude to Qm.n (signed 2's complement). + * The sign-bit BIT(m+n-1) and above are 0 for positive value and 1 for negative + * the range of value is [-2^(m-1), 2^(m-1) - 2^-n] + * + * For example + * A Q3.12 format number: + * - required bit: 3 + 12 = 15bits + * - range: [-2^2, 2^2 - 2^−15] + * + * NOTE: the m can be zero if all bit_precision are used to present fractional + * bits like Q0.32 + */ +u64 drm_color_ctm_s31_32_to_qm_n(u64 user_input, u32 m, u32 n) +{ + u64 mag = (user_input & ~BIT_ULL(63)) >> (32 - n); + bool negative = !!(user_input & BIT_ULL(63)); + s64 val; + + WARN_ON(m > 32 || n > 32); + + val = clamp_val(mag, 0, negative ? + BIT_ULL(n + m - 1) : BIT_ULL(n + m - 1) - 1); + + return negative ? -val : val; +} +EXPORT_SYMBOL(drm_color_ctm_s31_32_to_qm_n); + /** * drm_crtc_enable_color_mgmt - enable color management properties * @crtc: DRM CRTC diff --git a/include/drm/drm_color_mgmt.h b/include/drm/drm_color_mgmt.h index d1c662d92ab7..997a42ab29f5 100644 --- a/include/drm/drm_color_mgmt.h +++ b/include/drm/drm_color_mgmt.h @@ -30,6 +30,7 @@ struct drm_crtc; struct drm_plane;
uint32_t drm_color_lut_extract(uint32_t user_input, uint32_t bit_precision); +u64 drm_color_ctm_s31_32_to_qm_n(u64 user_input, u32 m, u32 n);
void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc, uint degamma_lut_size,