mesa-panvk-bifrost: r4 -> r5 — advertise fragmentStoresAndAtomics on Bifrost

Backports Mesa main's unconditional flip of .fragmentStoresAndAtomics
to true in src/panfrost/vulkan/panvk_vX_physical_device.c. Closes
the Dawn-WebGPU adapter rejection at PhysicalDeviceVk.cpp:250 that
caused brave-vulkan to fall back to the SwiftShader CPU adapter on
PineTab2/Mali-G52, per marfrit/panvk-bifrost#2.

Phase 7 verify on ohm (PineTab2, RK3566, Mali-G52 r1 MC1) with a
locally-built r5 lib installed to /tmp/r5_test_lib/:

  dEQP-VK.glsl.atomic_operations.*:
    r4:  48 pass /   0 fail / 992 NotSupported  (1040 total)
    r5:  80 pass /   0 fail / 960 NotSupported  (1040 total)
    delta: +32 newly-passing, zero new failures

  dEQP-VK.image.store.*:
    r4: 2772 pass /  0 fail / 238 NotSupported  (3010 total)
    r5: 2772 pass /  0 fail / 238 NotSupported  (3010 total)
    delta: identical (image.store is independent of the flag)

The disjunction with instance->force_enable_shader_atomics is kept as
a documented kill-switch even though the compiler folds it away —
it leaves the DRI option pan_force_enable_shader_atomics semantically
wired for future rebases or downstream debugging.

Patch reviewed via 2nd-model pass (per bugfix-process step 4):
recommended keeping the disjunction (applied), Bifrost-only-vs-unconditional
left unconditional to match upstream (applied), pre-ship CTS subset
(applied with results above).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

arch/mesa-panvk-bifrost/0005-panvk-bifrost-fragment-stores-atomics.patch

@@ -0,0 +1,50 @@
+From: marfrit-packages noether <claude-noether@reauktion.de>
+Subject: [PATCH] panvk: report fragmentStoresAndAtomics = true on Bifrost
+
+Backports Mesa main's unconditional advertisement of
+fragmentStoresAndAtomics for panvk (snapshot ref: src/panfrost/vulkan/
+panvk_vX_physical_device.c at commit-time 2026-05-06; the line reads
+`.fragmentStoresAndAtomics = true,` on main with no PAN_ARCH gate).
+
+Motivation: Chromium Dawn's WebGPU initializer in
+third_party/dawn/src/dawn/native/vulkan/PhysicalDeviceVk.cpp:250
+unconditionally rejects any Vulkan adapter that doesn't advertise this
+feature, causing Dawn to fall back to the SwiftShader CPU adapter
+on PineTab2 / RK3566 / Mali-G52 r1 MC1 (PAN_ARCH 7). With this patch the
+device advertises true, satisfying Dawn's gate. Tracked at
+https://git.reauktion.de/marfrit/panvk-bifrost/issues/2.
+
+The disjunction with `instance->force_enable_shader_atomics` is
+preserved as a kill-switch: in compiler terms it's dead code
+(`true || X == true`), but it leaves the DRI option
+`pan_force_enable_shader_atomics` semantically wired so future
+rebases or downstream debugging can see the link to the runtime knob.
+
+Caveat: the existing DRI option's description in src/util/driconf.h
+still labels this as "may not work reliably and is for debug purposes
+only". Mesa main's choice to ship it as default-on for all panvk
+architectures (including Bifrost, which is non-conformant per the
+PAN_I_WANT_A_BROKEN_VULKAN_DRIVER gate) reflects an upstream judgment
+that the practical risk is acceptable. Verify-before-ship for this
+package: dEQP-VK.glsl.atomic_operations.* + dEQP-VK.image.store.*
+deltas vs the r4 baseline must show no new fails. Pass counts may rise
+(tests that previously NotSupported now run); the load-bearing line is
+the Failed column staying at zero.
+
+---
+ src/panfrost/vulkan/panvk_vX_physical_device.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+diff --git a/src/panfrost/vulkan/panvk_vX_physical_device.c b/src/panfrost/vulkan/panvk_vX_physical_device.c
+--- a/src/panfrost/vulkan/panvk_vX_physical_device.c
++++ b/src/panfrost/vulkan/panvk_vX_physical_device.c
+@@ -280,8 +280,7 @@
+       .vertexPipelineStoresAndAtomics =
+          (PAN_ARCH >= 13 && instance->enable_vertex_pipeline_stores_atomics) ||
+          instance->force_enable_shader_atomics,
+-      .fragmentStoresAndAtomics =
+-         (PAN_ARCH >= 10) || instance->force_enable_shader_atomics,
++      .fragmentStoresAndAtomics = true || instance->force_enable_shader_atomics,
+       .shaderTessellationAndGeometryPointSize = false,
+       .shaderImageGatherExtended = true,
+       .shaderStorageImageExtendedFormats = true,

arch/mesa-panvk-bifrost/PKGBUILD

@@ -30,7 +30,7 @@
 
 pkgname=mesa-panvk-bifrost
 _mesaver=26.0.6
-pkgver=26.0.6.r4
+pkgver=26.0.6.r5
 pkgrel=1
 pkgdesc="Patched Mesa libvulkan_panfrost.so exposing Bifrost-gen Mali to Vulkan apps (panvk-bifrost campaign)"
 arch=('aarch64')
@@ -81,6 +81,7 @@ source=(
     "0002-panvk-expose-vulkan-1.1-1.2-on-bifrost.patch"
     "0003-panvk-bifrost-vk-ext-transform-feedback.patch"
     "0004-panvk-bifrost-xfb-primitive-decomposition.patch"
+    "0005-panvk-bifrost-fragment-stores-atomics.patch"
     "brave-vulkan"
     "icd.json"
 )
@@ -92,6 +93,7 @@ sha256sums=(
     'SKIP'
     'SKIP'
     'SKIP'
+    'SKIP'
 )
 
 prepare() {
@@ -127,6 +129,17 @@ prepare() {
     # Phase-doc context: ~/src/panvk-bifrost/iter17/phase{0,1,2,4,5,6,8}_*.md.
     patch -p1 < "${srcdir}/0004-panvk-bifrost-xfb-primitive-decomposition.patch"
 
+    # r5 (2026-05-23): advertise .fragmentStoresAndAtomics = true on Bifrost
+    # to satisfy Chromium Dawn's WebGPU init gate
+    # (third_party/dawn/src/dawn/native/vulkan/PhysicalDeviceVk.cpp:250).
+    # Backports Mesa main's unconditional flip (same line as on main as of
+    # 2026-05-06). Disjunction with instance->force_enable_shader_atomics
+    # is preserved as a documented kill-switch even though the compiler
+    # folds it away. Closes marfrit/panvk-bifrost#2.
+    # Verify-before-ship: dEQP-VK.glsl.atomic_operations.* and
+    # dEQP-VK.image.store.* show no new Failed vs r4 baseline.
+    patch -p1 < "${srcdir}/0005-panvk-bifrost-fragment-stores-atomics.patch"
+
     # Sanity-check the patches landed.
     grep -q "KHR_robustness2 = true," src/panfrost/vulkan/panvk_vX_physical_device.c
     grep -q "EXT_robustness2 = true," src/panfrost/vulkan/panvk_vX_physical_device.c
@@ -138,6 +151,8 @@ prepare() {
     test -f src/panfrost/vulkan/jm/panvk_vX_cmd_xfb.c
     # iter17 sanity: pan_nir_lower_xfb call site has been replaced; new file present.
     grep -q "panvk_per_arch(nir_lower_xfb)" src/panfrost/vulkan/panvk_vX_shader.c
+    # r5 sanity: fragmentStoresAndAtomics = true patch landed
+    grep -q "fragmentStoresAndAtomics = true ||" src/panfrost/vulkan/panvk_vX_physical_device.c
     grep -q "xfb_topology" src/panfrost/vulkan/panvk_shader.h
     grep -q "panvk_xfb_topology" src/panfrost/vulkan/panvk_shader.h
     test -f src/panfrost/vulkan/panvk_vX_xfb_lower.c