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linux/include/drm/drm_fixed.h
Imre Deak 58cd0cba82 drm: Add helpers for q4 fixed point values
Add helpers to convert between q4 fixed point and integer/fraction
values. Also add the format/argument macros required to printk q4 fixed
point variables. The q4 notation is based on the short variant described
by

https://en.wikipedia.org/wiki/Q_(number_format)

where only the number of fraction bits in the fixed point value are
defined, while the full size is deducted from the container type, that
is the size of int for these helpers. Using the fxp_ prefix, which makes
moving these helpers outside of drm to a more generic place easier, if
they prove to be useful.

These are needed by later patches dumping the Display Stream Compression
configuration in DRM core and in the i915 driver to replace the
corresponding bpp_x16 helpers defined locally in the driver.

v2: Use the more generic/descriptive fxp_q4 prefix instead of drm_x16.
   (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240628164451.1177612-2-imre.deak@intel.com
2024-07-03 18:05:12 +03:00

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C

/*
* Copyright 2009 Red Hat Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* Authors: Dave Airlie
* Christian König
*/
#ifndef DRM_FIXED_H
#define DRM_FIXED_H
#include <linux/kernel.h>
#include <linux/math64.h>
typedef union dfixed {
u32 full;
} fixed20_12;
#define dfixed_const(A) (u32)(((A) << 12))/* + ((B + 0.000122)*4096)) */
#define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
#define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
#define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
#define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
#define dfixed_init(A) { .full = dfixed_const((A)) }
#define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
#define dfixed_trunc(A) ((A).full >> 12)
#define dfixed_frac(A) ((A).full & ((1 << 12) - 1))
static inline u32 dfixed_floor(fixed20_12 A)
{
u32 non_frac = dfixed_trunc(A);
return dfixed_const(non_frac);
}
static inline u32 dfixed_ceil(fixed20_12 A)
{
u32 non_frac = dfixed_trunc(A);
if (A.full > dfixed_const(non_frac))
return dfixed_const(non_frac + 1);
else
return dfixed_const(non_frac);
}
static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
{
u64 tmp = ((u64)A.full << 13);
do_div(tmp, B.full);
tmp += 1;
tmp /= 2;
return lower_32_bits(tmp);
}
#define DRM_FIXED_POINT 32
#define DRM_FIXED_ONE (1ULL << DRM_FIXED_POINT)
#define DRM_FIXED_DECIMAL_MASK (DRM_FIXED_ONE - 1)
#define DRM_FIXED_DIGITS_MASK (~DRM_FIXED_DECIMAL_MASK)
#define DRM_FIXED_EPSILON 1LL
#define DRM_FIXED_ALMOST_ONE (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
static inline s64 drm_int2fixp(int a)
{
return ((s64)a) << DRM_FIXED_POINT;
}
static inline int drm_fixp2int(s64 a)
{
return ((s64)a) >> DRM_FIXED_POINT;
}
static inline int drm_fixp2int_round(s64 a)
{
return drm_fixp2int(a + DRM_FIXED_ONE / 2);
}
static inline int drm_fixp2int_ceil(s64 a)
{
if (a >= 0)
return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
else
return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
}
static inline unsigned drm_fixp_msbset(s64 a)
{
unsigned shift, sign = (a >> 63) & 1;
for (shift = 62; shift > 0; --shift)
if (((a >> shift) & 1) != sign)
return shift;
return 0;
}
static inline s64 drm_fixp_mul(s64 a, s64 b)
{
unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
s64 result;
if (shift > 61) {
shift = shift - 61;
a >>= (shift >> 1) + (shift & 1);
b >>= shift >> 1;
} else
shift = 0;
result = a * b;
if (shift > DRM_FIXED_POINT)
return result << (shift - DRM_FIXED_POINT);
if (shift < DRM_FIXED_POINT)
return result >> (DRM_FIXED_POINT - shift);
return result;
}
static inline s64 drm_fixp_div(s64 a, s64 b)
{
unsigned shift = 62 - drm_fixp_msbset(a);
s64 result;
a <<= shift;
if (shift < DRM_FIXED_POINT)
b >>= (DRM_FIXED_POINT - shift);
result = div64_s64(a, b);
if (shift > DRM_FIXED_POINT)
return result >> (shift - DRM_FIXED_POINT);
return result;
}
static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
{
s64 res;
bool a_neg = a < 0;
bool b_neg = b < 0;
u64 a_abs = a_neg ? -a : a;
u64 b_abs = b_neg ? -b : b;
u64 rem;
/* determine integer part */
u64 res_abs = div64_u64_rem(a_abs, b_abs, &rem);
/* determine fractional part */
{
u32 i = DRM_FIXED_POINT;
do {
rem <<= 1;
res_abs <<= 1;
if (rem >= b_abs) {
res_abs |= 1;
rem -= b_abs;
}
} while (--i != 0);
}
/* round up LSB */
{
u64 summand = (rem << 1) >= b_abs;
res_abs += summand;
}
res = (s64) res_abs;
if (a_neg ^ b_neg)
res = -res;
return res;
}
static inline s64 drm_fixp_exp(s64 x)
{
s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
s64 sum = DRM_FIXED_ONE, term, y = x;
u64 count = 1;
if (x < 0)
y = -1 * x;
term = y;
while (term >= tolerance) {
sum = sum + term;
count = count + 1;
term = drm_fixp_mul(term, div64_s64(y, count));
}
if (x < 0)
sum = drm_fixp_div(DRM_FIXED_ONE, sum);
return sum;
}
static inline int fxp_q4_from_int(int val_int)
{
return val_int << 4;
}
static inline int fxp_q4_to_int(int val_q4)
{
return val_q4 >> 4;
}
static inline int fxp_q4_to_int_roundup(int val_q4)
{
return (val_q4 + 0xf) >> 4;
}
static inline int fxp_q4_to_frac(int val_q4)
{
return val_q4 & 0xf;
}
#define FXP_Q4_FMT "%d.%04d"
#define FXP_Q4_ARGS(val_q4) fxp_q4_to_int(val_q4), (fxp_q4_to_frac(val_q4) * 625)
#endif