panfrost: Upload sample positions on device init

Needed to correctly implement multisampling on Bifrost, and used in
gl_SamplePosition  implementation on Midgard. These are architecturally
invariant, so it's fine to hard code.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8774>

src/panfrost/Makefile.sources

@@ -40,6 +40,7 @@ lib_FILES := \
         lib/pan_pool.h \
         lib/pan_props.c \
         lib/pan_sampler.c \
+        lib/pan_samples.c \
         lib/pan_shader.h \
         lib/pan_scoreboard.c \
         lib/pan_scoreboard.h \

src/panfrost/lib/meson.build

@@ -29,6 +29,7 @@ libpanfrost_lib_files = files(
   'pan_format.c',
   'pan_invocation.c',
   'pan_sampler.c',
+  'pan_samples.c',
   'pan_tiler.c',
   'pan_texture.c',
   'pan_scoreboard.c',

src/panfrost/lib/pan_device.h

@@ -159,6 +159,12 @@ struct panfrost_device {
          * we end up with tiler heap corruption.
          */
         pthread_mutex_t submit_lock;
+
+        /* Sample positions are preloaded into a write-once constant buffer,
+         * such that they can be referenced fore free later. Needed
+         * unconditionally on Bifrost, and useful for sharing with Midgard */
+
+        struct panfrost_bo *sample_positions;
 };
 
 void
@@ -170,6 +176,13 @@ panfrost_close_device(struct panfrost_device *dev);
 bool
 panfrost_supports_compressed_format(struct panfrost_device *dev, unsigned fmt);
 
+void
+panfrost_upload_sample_positions(struct panfrost_device *dev);
+
+mali_ptr
+panfrost_sample_positions(struct panfrost_device *dev,
+                enum mali_sample_pattern pattern);
+
 static inline struct panfrost_bo *
 pan_lookup_bo(struct panfrost_device *dev, uint32_t gem_handle)
 {

src/panfrost/lib/pan_props.c

@@ -255,6 +255,9 @@ panfrost_open_device(void *memctx, int fd, struct panfrost_device *dev)
                         PAN_BO_INVISIBLE | PAN_BO_GROWABLE);
 
         pthread_mutex_init(&dev->submit_lock, NULL);
+
+        /* Done once on init */
+        panfrost_upload_sample_positions(dev);
 }
 
 void

src/panfrost/lib/pan_samples.c

@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2019 Collabora, Ltd.
+ *
+ * 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 (including the next
+ * paragraph) 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 AUTHORS OR COPYRIGHT HOLDERS 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.
+ */
+
+#include "pan_device.h"
+#include "pan_bo.h"
+
+/* Sample positions are specified partially in hardware, partially in software
+ * on Mali. On Midgard, sample positions are completely fixed but need to be
+ * software accessible to implement gl_SamplePosition. On Bifrost, sample
+ * positions are part fixed, part programmable, and again need to be accessible
+ * for gl_SamplePosition. The mali_sample_position data structure is
+ * hardware-defined on Bifrost as a packed 8:8 fixed point format. The
+ * mali_sample_positions array is part-hardware, part-software-defined: it must
+ * give the sample position when indexed by the sample index, as well as
+ * reading back the origin when indexed by 32.
+ *
+ * The upshot is all of this is known at compile-time, so we can just hardcode
+ * the LUT, upload it to GPU memory on device initialization, and forget about
+ * it.
+ */
+
+struct mali_sample_position {
+        uint16_t x, y;
+} __attribute__((packed));
+
+struct mali_sample_positions {
+        struct mali_sample_position positions[32];
+        struct mali_sample_position origin;
+        struct mali_sample_position padding[64 - (32 + 1)];
+} __attribute__((packed));
+
+/* SAMPLE16 constructs a single sample in terms of 1/16's of the grid, centered
+ * at the origin. SAMPLE4/8 swap the units for legibility. */
+
+#define SAMPLE16(x, y) { \
+        (((x) + 8) * (256 / 16)), \
+        (((y) + 8) * (256 / 16)) \
+}
+
+#define SAMPLE8(x, y) SAMPLE16((x) * 2, (y) * 2)
+#define SAMPLE4(x, y) SAMPLE16((x) * 4, (y) * 4)
+
+const struct mali_sample_positions sample_position_lut[] = {
+        [MALI_SAMPLE_PATTERN_SINGLE_SAMPLED] = {
+                .positions = {
+                        SAMPLE4(0, 0)
+                },
+                .origin = SAMPLE4(0, 0)
+        },
+
+        [MALI_SAMPLE_PATTERN_ORDERED_4X_GRID] = {
+                .positions = {
+                        SAMPLE4(-1, -1),
+                        SAMPLE4( 1, -1),
+                        SAMPLE4(-1,  1),
+                        SAMPLE4( 1,  1),
+                },
+                .origin = SAMPLE4(0, 0)
+        },
+
+        [MALI_SAMPLE_PATTERN_ROTATED_4X_GRID] = {
+                .positions = {
+                        SAMPLE8(-1, -3),
+                        SAMPLE8( 3, -1),
+                        SAMPLE8(-3,  1),
+                        SAMPLE8( 1,  3),
+                },
+                .origin = SAMPLE8(0, 0)
+        },
+
+        [MALI_SAMPLE_PATTERN_D3D_8X_GRID] = {
+                .positions = {
+                        SAMPLE16( 1, -3),
+                        SAMPLE16(-1,  3),
+                        SAMPLE16( 5,  1),
+                        SAMPLE16(-3, -5),
+                        SAMPLE16(-5,  5),
+                        SAMPLE16(-7, -1),
+                        SAMPLE16( 3,  7),
+                        SAMPLE16( 7,  -7),
+                },
+                .origin = SAMPLE16(0, 0)
+        },
+
+        [MALI_SAMPLE_PATTERN_D3D_16X_GRID] = {
+                .positions = {
+                        SAMPLE16( 1,  1),
+                        SAMPLE16(-1, -3),
+                        SAMPLE16(-3,  2),
+                        SAMPLE16( 4, -1),
+                        SAMPLE16(-5, -2),
+                        SAMPLE16( 2,  5),
+                        SAMPLE16( 5,  3),
+                        SAMPLE16( 3, -5),
+                        SAMPLE16(-2,  6),
+                        SAMPLE16( 0,  7),
+                        SAMPLE16(-4, -6),
+                        SAMPLE16(-6,  4),
+                        SAMPLE16(-8,  0),
+                        SAMPLE16( 7, -4),
+                        SAMPLE16( 6,  7),
+                        SAMPLE16(-7, -8),
+
+                },
+                .origin = SAMPLE16(0, 0)
+        }
+};
+
+mali_ptr
+panfrost_sample_positions(struct panfrost_device *dev,
+                enum mali_sample_pattern pattern)
+{
+        assert(pattern < ARRAY_SIZE(sample_position_lut));
+        unsigned offset = (pattern * sizeof(sample_position_lut[0]));
+        return dev->sample_positions->ptr.gpu + offset;
+}
+
+void
+panfrost_upload_sample_positions(struct panfrost_device *dev)
+{
+        STATIC_ASSERT(sizeof(sample_position_lut) < 4096);
+        dev->sample_positions = panfrost_bo_create(dev, 4096, 0);
+
+        memcpy(dev->sample_positions->ptr.cpu, sample_position_lut,
+                        sizeof(sample_position_lut));
+}