diff options
Diffstat (limited to 'drivers/gpu/drm/radeon/r600_blit_kms.c')
| -rw-r--r-- | drivers/gpu/drm/radeon/r600_blit_kms.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/drivers/gpu/drm/radeon/r600_blit_kms.c b/drivers/gpu/drm/radeon/r600_blit_kms.c index e082dca6fee..9fb5780a552 100644 --- a/drivers/gpu/drm/radeon/r600_blit_kms.c +++ b/drivers/gpu/drm/radeon/r600_blit_kms.c @@ -31,6 +31,37 @@ #include "r600_blit_shaders.h" #include "radeon_blit_common.h" +/* 23 bits of float fractional data */ +#define I2F_FRAC_BITS 23 +#define I2F_MASK ((1 << I2F_FRAC_BITS) - 1) + +/* + * Converts unsigned integer into 32-bit IEEE floating point representation. + * Will be exact from 0 to 2^24. Above that, we round towards zero + * as the fractional bits will not fit in a float. (It would be better to + * round towards even as the fpu does, but that is slower.) + */ +__pure uint32_t int2float(uint32_t x) +{ + uint32_t msb, exponent, fraction; + + /* Zero is special */ + if (!x) return 0; + + /* Get location of the most significant bit */ + msb = __fls(x); + + /* + * Use a rotate instead of a shift because that works both leftwards + * and rightwards due to the mod(32) behaviour. This means we don't + * need to check to see if we are above 2^24 or not. + */ + fraction = ror32(x, (msb - I2F_FRAC_BITS) & 0x1f) & I2F_MASK; + exponent = (127 + msb) << I2F_FRAC_BITS; + + return fraction + exponent; +} + /* emits 21 on rv770+, 23 on r600 */ static void set_render_target(struct radeon_device *rdev, int format, |