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Diffstat (limited to 'drivers/gpu/drm/radeon/r600_blit_kms.c')
-rw-r--r--drivers/gpu/drm/radeon/r600_blit_kms.c31
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 e082dca6feee..9fb5780a552f 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,