From e2dcac91d202ba9d88c3f235dacedfcd0737ad77 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <dmalyshau@mozilla.com>
Date: Tue, 23 Apr 2019 16:27:39 -0400
Subject: [PATCH] Round up mappable buffer size to non-coherent atom, if needed

---
 wgpu-native/src/device.rs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/wgpu-native/src/device.rs b/wgpu-native/src/device.rs
index e7f7655901..fd78438470 100644
--- a/wgpu-native/src/device.rs
+++ b/wgpu-native/src/device.rs
@@ -502,10 +502,20 @@ pub fn device_create_buffer(
         .unwrap()
         .into();
     // TODO: allocate with rendy
+
+    // if the memory is mapped but not coherent, round up to the atom size
+    let mut mem_size = requirements.size;
+    if memory_properties.contains(hal::memory::Properties::CPU_VISIBLE) &&
+        !memory_properties.contains(hal::memory::Properties::COHERENT)
+    {
+        let mask = device.limits.non_coherent_atom_size as u64 - 1;
+        mem_size = ((mem_size - 1 ) | mask) + 1;
+    }
+
     let memory = unsafe {
         device
             .raw
-            .allocate_memory(device_type, requirements.size)
+            .allocate_memory(device_type, mem_size)
             .unwrap()
     };
     unsafe {