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drm: Add a new helper drm_color_ctm_s31_32_to_qm_n()

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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'
V9: Rebase.

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20191112110927.20931-2-james.qian.wang@arm.com
This commit is contained in:
james qian wang (Arm Technology China) 2019-11-12 11:09:59 +00:00
parent 4773483568
commit 7ca7fcef13
2 changed files with 35 additions and 0 deletions
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34
drivers/gpu/drm/drm_color_mgmt.c
View File

@ -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

1
include/drm/drm_color_mgmt.h
View File

@ -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,