Mesa (master): panfrost: Add negative lod bias support

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Module: Mesa
Branch: master
Commit: f2f12776248874b2a689cbba8faeb6e4e2144354
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f2f12776248874b2a689cbba8faeb6e4e2144354

Author: Icecream95 <ixn at keemail.me>
Date:   Thu Jan  9 15:13:58 2020 +1300

panfrost: Add negative lod bias support

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>

---

 src/gallium/drivers/panfrost/pan_context.c |  6 +++---
 src/panfrost/include/panfrost-job.h        | 20 +++++++++++---------
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/src/gallium/drivers/panfrost/pan_context.c b/src/gallium/drivers/panfrost/pan_context.c
index 647aa704ed3..d65d2863334 100644
--- a/src/gallium/drivers/panfrost/pan_context.c
+++ b/src/gallium/drivers/panfrost/pan_context.c
@@ -1801,9 +1801,9 @@ panfrost_create_sampler_state(
                         cso->border_color.f[2],
                         cso->border_color.f[3]
                 },
-                .min_lod = FIXED_16(cso->min_lod),
-                .max_lod = FIXED_16(cso->max_lod),
-                .lod_bias = FIXED_16(cso->lod_bias),
+                .min_lod = FIXED_16(cso->min_lod, false), /* clamp at 0 */
+                .max_lod = FIXED_16(cso->max_lod, false),
+                .lod_bias = FIXED_16(cso->lod_bias, true), /* can be negative */
                 .seamless_cube_map = cso->seamless_cube_map,
         };
 
diff --git a/src/panfrost/include/panfrost-job.h b/src/panfrost/include/panfrost-job.h
index 49c55f1f93e..dfc5d83a80d 100644
--- a/src/panfrost/include/panfrost-job.h
+++ b/src/panfrost/include/panfrost-job.h
@@ -29,6 +29,7 @@
 #define __PANFROST_JOB_H__
 
 #include <stdint.h>
+#include <stdbool.h>
 #include <panfrost-misc.h>
 
 enum mali_job_type {
@@ -1253,13 +1254,14 @@ struct mali_texture_descriptor {
 
 #define DECODE_FIXED_16(x) ((float) (x / 256.0))
 
-static inline uint16_t
-FIXED_16(float x)
+static inline int16_t
+FIXED_16(float x, bool allow_negative)
 {
         /* Clamp inputs, accounting for float error */
         float max_lod = (32.0 - (1.0 / 512.0));
+        float min_lod = allow_negative ? -max_lod : 0.0;
 
-        x = ((x > max_lod) ? max_lod : ((x < 0.0) ? 0.0 : x));
+        x = ((x > max_lod) ? max_lod : ((x < min_lod) ? min_lod : x));
 
         return (int) (x * 256.0);
 }
@@ -1267,13 +1269,13 @@ FIXED_16(float x)
 struct mali_sampler_descriptor {
         uint16_t filter_mode;
 
-        /* Fixed point. Upper 8-bits is before the decimal point, although it
-         * caps [0-31]. Lower 8-bits is after the decimal point: int(round(x *
-         * 256)) */
+        /* Fixed point, signed.
+         * Upper 7 bits before the decimal point, although it caps [0-31].
+         * Lower 8 bits after the decimal point: int(round(x * 256)) */
 
-        uint16_t lod_bias;
-        uint16_t min_lod;
-        uint16_t max_lod;
+        int16_t lod_bias;
+        int16_t min_lod;
+        int16_t max_lod;
 
         /* All one word in reality, but packed a bit. Comparisons are flipped
          * from OpenGL. */