panvk: Always set pan_fb_layout.rt_count to at least 1

Instead of having the pan_fb code have to `max(rt_count, 1)` add then
constantly be doing the same in the driver, just make the condition an
assert and do the `max(colorAttachmentCount, 1)` up-front.  This way
we're not constantly worried if everyone has the same count or not.  The
pan_fb code will handle having an empty render target just fine.

Reviewed-by: Lars-Ivar Hesselberg Simonsen <lars-ivar.simonsen@arm.com>
Acked-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Eric R. Smith <eric.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39759>

src/panfrost/lib/pan_fb.c

@@ -429,8 +429,6 @@ GENX(pan_emit_fb_desc)(const struct pan_fb_desc_info *info, void *out)
    const struct pan_fb_store *store = info->store;
 
    const bool has_zs_crc_ext = pan_fb_has_zs(fb);
-   assert(fb->rt_count > 0 || fb->rt_formats[0] == PIPE_FORMAT_NONE);
-   const unsigned rt_count = MAX2(fb->rt_count, 1);
 
    struct mali_framebuffer_packed fbd = {};
 
@@ -502,7 +500,8 @@ GENX(pan_emit_fb_desc)(const struct pan_fb_desc_info *info, void *out)
       cfg.first_provoking_vertex = info->provoking_vertex_first;
 #endif
 
-      cfg.render_target_count = rt_count;
+      assert(fb->rt_count > 0);
+      cfg.render_target_count = fb->rt_count;
       cfg.color_buffer_allocation = fb->tile_rt_alloc_B;
 
       if (fb->s_format != PIPE_FORMAT_NONE) {
@@ -553,7 +552,7 @@ GENX(pan_emit_fb_desc)(const struct pan_fb_desc_info *info, void *out)
    }
 
    uint32_t tile_rt_offset_B = 0;
-   for (unsigned rt = 0; rt < rt_count; rt++) {
+   for (unsigned rt = 0; rt < fb->rt_count; rt++) {
       struct mali_rgb_render_target_packed rgb_rt;
       emit_rgb_rt_desc(info, rt, tile_rt_offset_B, &rgb_rt);
       memcpy(out, &rgb_rt, sizeof(rgb_rt));
@@ -569,7 +568,7 @@ GENX(pan_emit_fb_desc)(const struct pan_fb_desc_info *info, void *out)
    struct mali_framebuffer_pointer_packed tag;
    pan_pack(&tag, FRAMEBUFFER_POINTER, cfg) {
       cfg.zs_crc_extension_present = has_zs_crc_ext;
-      cfg.render_target_count = rt_count;
+      cfg.render_target_count = fb->rt_count;
    }
    return tag.opaque[0];
 }

src/panfrost/vulkan/csf/panvk_vX_cmd_draw.c

@@ -133,9 +133,8 @@ calc_fn_set_fbds_provoking_vertex_idx(struct panvk_cmd_buffer *cmdbuf)
 {
    const struct pan_fb_layout *fb = &cmdbuf->state.gfx.render.fb.layout;
    const bool has_zs_ext = pan_fb_has_zs(fb);
-   uint32_t rt_count = MAX2(fb->rt_count, 1);
 
-   return get_fn_set_fbds_provoking_vertex_idx(has_zs_ext, rt_count);
+   return get_fn_set_fbds_provoking_vertex_idx(has_zs_ext, fb->rt_count);
 }
 
 VkResult
@@ -663,7 +662,7 @@ prepare_blend(struct panvk_cmd_buffer *cmdbuf)
 
    const struct panvk_shader_variant *fs =
       panvk_shader_only_variant(get_fs(cmdbuf));
-   uint32_t bd_count = MAX2(cmdbuf->state.gfx.render.fb.layout.rt_count, 1);
+   uint32_t bd_count = cmdbuf->state.gfx.render.fb.layout.rt_count;
    struct cs_builder *b =
       panvk_get_cs_builder(cmdbuf, PANVK_SUBQUEUE_VERTEX_TILER);
    struct pan_ptr ptr = panvk_cmd_alloc_desc_array(cmdbuf, bd_count, BLEND);
@@ -927,9 +926,8 @@ calc_fbd_size(struct panvk_cmd_buffer *cmdbuf)
 {
    const struct pan_fb_layout *fb = &cmdbuf->state.gfx.render.fb.layout;
    const bool has_zs_ext = pan_fb_has_zs(fb);
-   uint32_t rt_count = MAX2(fb->rt_count, 1);
 
-   return get_fbd_size(has_zs_ext, rt_count);
+   return get_fbd_size(has_zs_ext, fb->rt_count);
 }
 
 static uint32_t
@@ -1329,7 +1327,7 @@ get_fb_descs(struct panvk_cmd_buffer *cmdbuf)
    }
 
    const bool has_zs_ext = pan_fb_has_zs(&render->fb.layout);
-   const uint32_t rt_count = MAX2(render->fb.layout.rt_count, 1);
+   const uint32_t rt_count = render->fb.layout.rt_count;
 
    struct cs_builder *b = panvk_get_cs_builder(cmdbuf, PANVK_SUBQUEUE_FRAGMENT);
    for (uint32_t ir_pass = 0; ir_pass < PANVK_IR_PASS_COUNT; ir_pass++) {
@@ -2990,7 +2988,7 @@ panvk_per_arch(cmd_inherit_render_state)(
           render->fb.layout.sample_count == sample_count);
    render->fb.layout = (struct pan_fb_layout) {
       .sample_count = sample_count,
-      .rt_count = inheritance_info->colorAttachmentCount,
+      .rt_count = MAX2(inheritance_info->colorAttachmentCount, 1),
 
       .tile_size_px = render->fb.layout.tile_size_px,
       .tile_rt_alloc_B = render->fb.layout.tile_rt_alloc_B,
@@ -3324,9 +3322,8 @@ calc_tiler_oom_handler_idx(struct panvk_cmd_buffer *cmdbuf)
 {
    const struct pan_fb_layout *fb = &cmdbuf->state.gfx.render.fb.layout;
    const bool has_zs_ext = pan_fb_has_zs(fb);
-   uint32_t rt_count = MAX2(fb->rt_count, 1);
 
-   return get_tiler_oom_handler_idx(has_zs_ext, rt_count);
+   return get_tiler_oom_handler_idx(has_zs_ext, fb->rt_count);
 }
 
 static void
@@ -3475,7 +3472,7 @@ issue_fragment_jobs(struct panvk_cmd_buffer *cmdbuf)
    }
 
    const bool has_zs_ext = pan_fb_has_zs(fb);
-   const uint32_t rt_count = MAX2(fb->rt_count, 1);
+   const uint32_t rt_count = fb->rt_count;
 
    /* IR was hit: set up IR FBD */
    cs_if(b, MALI_CS_CONDITION_GREATER, counter) {

src/panfrost/vulkan/jm/panvk_vX_cmd_buffer.c

@@ -214,7 +214,7 @@ panvk_per_arch(cmd_alloc_fb_desc)(struct panvk_cmd_buffer *cmdbuf)
                  pan_size(ZS_CRC_EXTENSION);
 
    fbd_size = ALIGN_POT(fbd_size, pan_alignment(RENDER_TARGET)) +
-              (MAX2(fb->rt_count, 1) * pan_size(RENDER_TARGET));
+              (fb->rt_count * pan_size(RENDER_TARGET));
 
    batch->fb.bo_count = cmdbuf->state.gfx.render.fb.bo_count;
    memcpy(batch->fb.bos, cmdbuf->state.gfx.render.fb.bos,

src/panfrost/vulkan/jm/panvk_vX_cmd_draw.c

@@ -241,7 +241,7 @@ panvk_draw_prepare_fs_rsd(struct panvk_cmd_buffer *cmdbuf,
    const struct panvk_shader_variant *fs =
       panvk_shader_only_variant(get_fs(cmdbuf));
    const struct pan_shader_info *fs_info = fs ? &fs->info : NULL;
-   uint32_t bd_count = MAX2(cmdbuf->state.gfx.render.fb.layout.rt_count, 1);
+   uint32_t bd_count = cmdbuf->state.gfx.render.fb.layout.rt_count;
    bool test_s = has_stencil_att(cmdbuf) && ds->stencil.test_enable;
    bool test_z = has_depth_att(cmdbuf) && ds->depth.test_enable;
    bool writes_z = writes_depth(cmdbuf);

src/panfrost/vulkan/panvk_vX_blend.c

@@ -296,7 +296,6 @@ panvk_per_arch(blend_emit_descs)(struct panvk_cmd_buffer *cmdbuf,
    uint64_t blend_shaders[8] = {};
    /* All bits set to one encodes unused fixed-function blend constant. */
    unsigned ff_blend_constant = ~0;
-   uint32_t blend_count = MAX2(cmdbuf->state.gfx.render.fb.layout.rt_count, 1);
 
    uint8_t loc_rt[MAX_RTS], rt_loc[MAX_RTS];
    memset(loc_rt, MESA_VK_ATTACHMENT_UNUSED, sizeof(loc_rt));
@@ -380,13 +379,13 @@ panvk_per_arch(blend_emit_descs)(struct panvk_cmd_buffer *cmdbuf,
       ff_blend_constant = 0;
 
    struct mali_blend_packed packed[MAX_RTS];
-   for (uint8_t rt = 0; rt < blend_count; rt++) {
+   for (uint8_t rt = 0; rt < bs.rt_count; rt++) {
       emit_blend_desc(&bs, rt, fs_info, rt_loc[rt], fs_code,
                       blend_shaders[rt], ff_blend_constant, &packed[rt]);
    }
 
    /* Copy into the GPU descriptor array */
-   typed_memcpy(bds, packed, blend_count);
+   typed_memcpy(bds, packed, bs.rt_count);
 
    /* Re-order blend descriptors for the shader
     *

src/panfrost/vulkan/panvk_vX_cmd_draw.c

@@ -471,7 +471,11 @@ panvk_per_arch(cmd_init_render_state)(struct panvk_cmd_buffer *cmdbuf,
        * value if we don't set it here already.
        */
       .sample_count = 0,
-      .rt_count = pRenderingInfo->colorAttachmentCount,
+
+      /* The hardware requires us to have at least one color target, even if
+       * it's a dummy.
+       */
+      .rt_count = MAX2(pRenderingInfo->colorAttachmentCount, 1),
 
       .tile_rt_budget_B =
          pan_query_optimal_tib_size(PAN_ARCH, phys_dev->model),

src/panfrost/vulkan/panvk_vX_cmd_fb_preload.c

@@ -349,9 +349,7 @@ fill_bds(const struct pan_fb_layout *fb,
          const struct panvk_fb_preload_shader_key *key,
          struct mali_blend_packed *bds)
 {
-   uint32_t bd_count = MAX2(fb->rt_count, 1);
-
-   for (unsigned i = 0; i < bd_count; i++) {
+   for (unsigned i = 0; i < fb->rt_count; i++) {
       pan_pack(&bds[i], BLEND, cfg) {
          if (!pan_fb_shader_key_target_written(&key->key.rts[i]) ||
              fb->rt_formats[i] == PIPE_FORMAT_NONE) {
@@ -421,7 +419,7 @@ cmd_emit_dcd(struct panvk_cmd_buffer *cmdbuf,
    assert(preload_color != (preload_z || preload_s));
 
    uint32_t tex_count = util_bitcount(locations_written);
-   uint32_t bd_count = MAX2(fb->rt_count, 1);
+   uint32_t bd_count = fb->rt_count;
 
    struct pan_ptr rsd = panvk_cmd_alloc_desc_aggregate(
       cmdbuf, PAN_DESC(RENDERER_STATE),