pan/midgard: Implement load_sampler_lod_paramaters_pan

We can stuff this information in as parametrized system values, like we
currently do texture size and SSBO addresses.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>

src/gallium/drivers/panfrost/pan_context.c

@@ -761,6 +761,29 @@ static void panfrost_upload_ssbo_sysval(
         uniform->u[2] = sb.buffer_size;
 }
 
+static void
+panfrost_upload_sampler_sysval(
+                struct panfrost_context *ctx,
+                enum pipe_shader_type st,
+                unsigned sampler_index,
+                struct sysval_uniform *uniform)
+{
+        struct pipe_sampler_state *sampl =
+                &ctx->samplers[st][sampler_index]->base;
+
+        uniform->f[0] = sampl->min_lod;
+        uniform->f[1] = sampl->max_lod;
+        uniform->f[2] = sampl->lod_bias;
+
+        /* Even without any errata, Midgard represents "no mipmapping" as
+         * fixing the LOD with the clamps; keep behaviour consistent. c.f.
+         * panfrost_create_sampler_state which also explains our choice of
+         * epsilon value (again to keep behaviour consistent) */
+
+        if (sampl->min_mip_filter == PIPE_TEX_MIPFILTER_NONE)
+                uniform->f[1] = uniform->f[0] + (1.0/256.0);
+}
+
 static void panfrost_upload_num_work_groups_sysval(struct panfrost_context *ctx,
                 struct sysval_uniform *uniform)
 {
@@ -796,7 +819,10 @@ static void panfrost_upload_sysvals(struct panfrost_context *ctx, void *buf,
                 case PAN_SYSVAL_NUM_WORK_GROUPS:
                         panfrost_upload_num_work_groups_sysval(ctx, &uniforms[i]);
                         break;
-
+                case PAN_SYSVAL_SAMPLER:
+                        panfrost_upload_sampler_sysval(ctx, st, PAN_SYSVAL_ID(sysval),
+                                                    &uniforms[i]);
+                        break;
                 default:
                         assert(0);
                 }

src/panfrost/midgard/midgard_compile.c

@@ -345,6 +345,17 @@ midgard_sysval_for_ssbo(nir_intrinsic_instr *instr)
         return PAN_SYSVAL(SSBO, uindex);
 }
 
+static int
+midgard_sysval_for_sampler(nir_intrinsic_instr *instr)
+{
+        /* TODO: indirect samplers !!! */
+        nir_src index = instr->src[0];
+        assert(nir_src_is_const(index));
+        uint32_t uindex = nir_src_as_uint(index);
+
+        return PAN_SYSVAL(SAMPLER, uindex);
+}
+
 static int
 midgard_nir_sysval_for_intrinsic(nir_intrinsic_instr *instr)
 {
@@ -358,6 +369,8 @@ midgard_nir_sysval_for_intrinsic(nir_intrinsic_instr *instr)
         case nir_intrinsic_load_ssbo: 
         case nir_intrinsic_store_ssbo: 
                 return midgard_sysval_for_ssbo(instr);
+        case nir_intrinsic_load_sampler_lod_parameters_pan:
+                return midgard_sysval_for_sampler(instr);
         default:
                 return ~0;
         }
@@ -1591,6 +1604,7 @@ emit_intrinsic(compiler_context *ctx, nir_intrinsic_instr *instr)
         case nir_intrinsic_load_viewport_scale:
         case nir_intrinsic_load_viewport_offset:
         case nir_intrinsic_load_num_work_groups:
+        case nir_intrinsic_load_sampler_lod_parameters_pan:
                 emit_sysval_read(ctx, &instr->instr, ~0, 3);
                 break;
 

src/panfrost/midgard/midgard_compile.h

@@ -47,6 +47,7 @@ enum {
         PAN_SYSVAL_TEXTURE_SIZE = 3,
         PAN_SYSVAL_SSBO = 4,
         PAN_SYSVAL_NUM_WORK_GROUPS = 5,
+        PAN_SYSVAL_SAMPLER = 7,
 } pan_sysval;
 
 #define PAN_TXS_SYSVAL_ID(texidx, dim, is_array)          \