diff --git a/.github/workflows/blake2.yml b/.github/workflows/blake2.yml
index b2c64f7fb..acfe035cd 100644
--- a/.github/workflows/blake2.yml
+++ b/.github/workflows/blake2.yml
@@ -17,30 +17,28 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
-  # TODO(tarcieri): re-enable these when failures are addressed:
-  # <https://github.com/RustCrypto/hashes/pull/228/checks?check_run_id=1831937705>
-#  build:
-#    runs-on: ubuntu-latest
-#    strategy:
-#      matrix:
-#        rust:
-#          - 1.41.0 # MSRV
-#          - stable
-#        target:
-#          - thumbv7em-none-eabi
-#          - wasm32-unknown-unknown
-#    steps:
-#      - uses: actions/checkout@v1
-#      - uses: actions-rs/toolchain@v1
-#        with:
-#          profile: minimal
-#          toolchain: ${{ matrix.rust }}
-#          target: ${{ matrix.target }}
-#          override: true
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features blake2b
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features blake2s
-#      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features blake2b,blake2s
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.41.0 # MSRV
+          - stable
+        target:
+          - thumbv7em-none-eabi
+          - wasm32-unknown-unknown
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ matrix.rust }}
+          target: ${{ matrix.target }}
+          override: true
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features blake2b
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features blake2s
+      - run: cargo build --target ${{ matrix.target }} --release --no-default-features --features blake2b,blake2s
 
   test:
     runs-on: ubuntu-latest
diff --git a/blake2/Cargo.toml b/blake2/Cargo.toml
index 5c8e7927d..b77a9c4c0 100644
--- a/blake2/Cargo.toml
+++ b/blake2/Cargo.toml
@@ -17,7 +17,7 @@ arrayvec = { version = "0.5", default-features = false }
 crypto-mac = "0.8"
 digest = "0.9"
 opaque-debug = "0.3"
-subtle = ">=2, <2.5"
+subtle = { version = ">=2, <2.5", default-features = false }
 
 [dev-dependencies]
 crypto-mac = { version = "0.8", features = ["dev"] }
@@ -39,3 +39,7 @@ blake2s = []
 # performance. This feature disables some inlining, improving the performance
 # of the portable implementation in that specific case.
 uninline_portable = []
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
diff --git a/blake2/src/blake2b.rs b/blake2/src/blake2b.rs
index 1033ad558..bc1c55a61 100644
--- a/blake2/src/blake2b.rs
+++ b/blake2/src/blake2b.rs
@@ -24,9 +24,12 @@
 //! ```
 
 pub(crate) mod backend;
-pub mod many;
 pub(crate) mod state;
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+#[cfg_attr(docsrs, doc(cfg(any(target_arch = "x86", target_arch = "x86_64"))))]
+pub mod many;
+
 mod hash;
 mod params;
 #[cfg(test)]
@@ -280,10 +283,10 @@ pub(crate) fn paint_test_input(buf: &mut [u8]) {
 
 // This module is pub for internal benchmarks only. Please don't use it.
 #[doc(hidden)]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 pub mod benchmarks {
-    use crate::blake2bp;
-
     use super::*;
+    use crate::blake2bp;
 
     pub fn force_portable(params: &mut Params) {
         params.implementation = backend::Implementation::portable();
diff --git a/blake2/src/blake2b/backend.rs b/blake2/src/blake2b/backend.rs
index 21e30642a..5942eb252 100644
--- a/blake2/src/blake2b/backend.rs
+++ b/blake2/src/blake2b/backend.rs
@@ -13,9 +13,6 @@ use core::cmp;
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 pub const MAX_DEGREE: usize = 4;
 
-#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
-pub const MAX_DEGREE: usize = 1;
-
 /// Variants other than Portable are unreachable in no_std, unless CPU features
 /// are explicitly enabled for the build with e.g. RUSTFLAGS="-C target-feature=avx2".
 /// This might change in the future if is_x86_feature_detected moves into libcore.
@@ -91,11 +88,10 @@ impl Implementation {
         None
     }
 
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     pub fn degree(&self) -> usize {
         match self.0 {
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Avx2 => avx2::DEGREE,
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Sse41 => sse41::DEGREE,
             Platform::Portable => 1,
         }
@@ -123,9 +119,9 @@ impl Implementation {
         }
     }
 
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     pub fn compress2_loop(&self, jobs: &mut [Job<'_, '_>; 2], finalize: Finalize, stride: Stride) {
         match self.0 {
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Avx2 | Platform::Sse41 => unsafe {
                 sse41::compress2_loop(jobs, finalize, stride)
             },
@@ -133,9 +129,9 @@ impl Implementation {
         }
     }
 
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     pub fn compress4_loop(&self, jobs: &mut [Job<'_, '_>; 4], finalize: Finalize, stride: Stride) {
         match self.0 {
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Avx2 => unsafe { avx2::compress4_loop(jobs, finalize, stride) },
             _ => panic!("unsupported"),
         }
@@ -196,7 +192,8 @@ impl LastNode {
 
 #[derive(Clone, Copy, Debug)]
 pub enum Stride {
-    Serial,   // BLAKE2b/BLAKE2s
+    Serial, // BLAKE2b/BLAKE2s
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     Parallel, // BLAKE2bp/BLAKE2sp
 }
 
@@ -204,6 +201,7 @@ impl Stride {
     pub fn padded_blockbytes(&self) -> usize {
         match self {
             Stride::Serial => BLOCKBYTES,
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Stride::Parallel => crate::blake2bp::DEGREE * BLOCKBYTES,
         }
     }
@@ -217,6 +215,7 @@ pub(crate) fn count_high(count: Count) -> Word {
     (count >> (8 * size_of::<Word>())) as Word
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 pub(crate) fn assemble_count(low: Word, high: Word) -> Count {
     low as Count + ((high as Count) << (8 * size_of::<Word>()))
 }
diff --git a/blake2/src/blake2b/test.rs b/blake2/src/blake2b/test.rs
index a53c2b7a9..f27b0cac0 100644
--- a/blake2/src/blake2b/test.rs
+++ b/blake2/src/blake2b/test.rs
@@ -1,4 +1,6 @@
 use super::*;
+
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 use crate::blake2bp;
 
 const EMPTY_HASH: &str = "786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419\
@@ -120,6 +122,7 @@ fn test_all_parameters() {
     );
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 fn test_all_parameters_blake2bp() {
     let mut params = crate::blake2bp::Params::new();
@@ -183,18 +186,21 @@ fn test_long_inner_hash_length_panics() {
     Params::new().inner_hash_length(OUTBYTES + 1);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2bp_short_hash_length_panics() {
     blake2bp::Params::new().hash_length(0);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2bp_long_hash_length_panics() {
     blake2bp::Params::new().hash_length(OUTBYTES + 1);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2bp_long_key_panics() {
diff --git a/blake2/src/blake2bp.rs b/blake2/src/blake2bp.rs
index 7da9f8b00..ad8b7c246 100644
--- a/blake2/src/blake2bp.rs
+++ b/blake2/src/blake2bp.rs
@@ -27,9 +27,6 @@ use crate::blake2b::{
 };
 use core::{cmp, fmt, mem::size_of};
 
-#[cfg(feature = "std")]
-use std;
-
 pub(crate) const DEGREE: usize = 4;
 
 /// Compute the BLAKE2bp hash of a slice of bytes all at once, using default
diff --git a/blake2/src/blake2s.rs b/blake2/src/blake2s.rs
index 4e0455578..664cff353 100644
--- a/blake2/src/blake2s.rs
+++ b/blake2/src/blake2s.rs
@@ -23,9 +23,12 @@
 //! ```
 
 pub(crate) mod backend;
-pub mod many;
 pub(crate) mod state;
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+#[cfg_attr(docsrs, doc(cfg(any(target_arch = "x86", target_arch = "x86_64"))))]
+pub mod many;
+
 mod hash;
 mod params;
 #[cfg(test)]
@@ -33,7 +36,6 @@ mod test;
 
 pub use self::{hash::Hash, params::Params, state::State};
 
-use crate::blake2sp;
 use core::{fmt, mem::size_of};
 use crypto_mac::{InvalidKeyLength, Mac, NewMac};
 use digest::{
@@ -270,8 +272,10 @@ pub(crate) fn paint_test_input(buf: &mut [u8]) {
 
 // This module is pub for internal benchmarks only. Please don't use it.
 #[doc(hidden)]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 pub mod benchmarks {
     use super::*;
+    use crate::blake2sp;
 
     pub fn force_portable(params: &mut Params) {
         params.implementation = backend::Implementation::portable();
diff --git a/blake2/src/blake2s/backend.rs b/blake2/src/blake2s/backend.rs
index 6a0b53110..c9473566d 100644
--- a/blake2/src/blake2s/backend.rs
+++ b/blake2/src/blake2s/backend.rs
@@ -13,9 +13,6 @@ use core::cmp;
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 pub const MAX_DEGREE: usize = 8;
 
-#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
-pub const MAX_DEGREE: usize = 1;
-
 /// Variants other than Portable are unreachable in no_std, unless CPU features
 /// are explicitly enabled for the build with e.g. RUSTFLAGS="-C target-feature=avx2".
 /// This might change in the future if is_x86_feature_detected moves into libcore.
@@ -91,11 +88,10 @@ impl Implementation {
         None
     }
 
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     pub fn degree(&self) -> usize {
         match self.0 {
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Avx2 => avx2::DEGREE,
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Sse41 => sse41::DEGREE,
             Platform::Portable => 1,
         }
@@ -121,9 +117,9 @@ impl Implementation {
         }
     }
 
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     pub fn compress4_loop(&self, jobs: &mut [Job<'_, '_>; 4], finalize: Finalize, stride: Stride) {
         match self.0 {
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Avx2 | Platform::Sse41 => unsafe {
                 sse41::compress4_loop(jobs, finalize, stride)
             },
@@ -131,9 +127,9 @@ impl Implementation {
         }
     }
 
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     pub fn compress8_loop(&self, jobs: &mut [Job<'_, '_>; 8], finalize: Finalize, stride: Stride) {
         match self.0 {
-            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::Avx2 => unsafe { avx2::compress8_loop(jobs, finalize, stride) },
             _ => panic!("unsupported"),
         }
@@ -194,7 +190,8 @@ impl LastNode {
 
 #[derive(Clone, Copy, Debug)]
 pub enum Stride {
-    Serial,   // BLAKE2b/BLAKE2s
+    Serial, // BLAKE2b/BLAKE2s
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     Parallel, // BLAKE2bp/BLAKE2sp
 }
 
@@ -202,6 +199,7 @@ impl Stride {
     pub fn padded_blockbytes(&self) -> usize {
         match self {
             Stride::Serial => BLOCKBYTES,
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Stride::Parallel => crate::blake2sp::DEGREE * BLOCKBYTES,
         }
     }
@@ -215,6 +213,7 @@ pub(crate) fn count_high(count: Count) -> Word {
     (count >> (8 * size_of::<Word>())) as Word
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 pub(crate) fn assemble_count(low: Word, high: Word) -> Count {
     low as Count + ((high as Count) << (8 * size_of::<Word>()))
 }
diff --git a/blake2/src/blake2s/test.rs b/blake2/src/blake2s/test.rs
index 063d6bf99..77941a245 100644
--- a/blake2/src/blake2s/test.rs
+++ b/blake2/src/blake2s/test.rs
@@ -1,5 +1,8 @@
 use super::*;
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+use crate::blake2sp;
+
 const EMPTY_HASH: &str = "69217a3079908094e11121d042354a7c1f55b6482ca1a51e1b250dfd1ed0eef9";
 const ABC_HASH: &str = "508c5e8c327c14e2e1a72ba34eeb452f37458b209ed63a294d999b4c86675982";
 const ONE_BLOCK_HASH: &str = "ae09db7cd54f42b490ef09b6bc541af688e4959bb8c53f359a6f56e38ab454a3";
@@ -115,6 +118,7 @@ fn test_all_parameters() {
     );
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 fn test_all_parameters_blake2sp() {
     let mut params = blake2sp::Params::new();
@@ -178,29 +182,34 @@ fn test_long_inner_hash_length_panics() {
     Params::new().inner_hash_length(OUTBYTES + 1);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2sp_short_hash_length_panics() {
     blake2sp::Params::new().hash_length(0);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2sp_long_hash_length_panics() {
     blake2sp::Params::new().hash_length(OUTBYTES + 1);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2sp_long_key_panics() {
     blake2sp::Params::new().key(&[0; KEYBYTES + 1]);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 fn test_blake2sp_max_offset_ok() {
     Params::new().node_offset((1 << 48) - 1);
 }
 
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[test]
 #[should_panic]
 fn test_blake2sp_offset_too_large_panics() {
diff --git a/blake2/src/blake2sp.rs b/blake2/src/blake2sp.rs
index 4baa8a8cd..023d97585 100644
--- a/blake2/src/blake2sp.rs
+++ b/blake2/src/blake2sp.rs
@@ -27,9 +27,6 @@ use crate::blake2s::{
 };
 use core::{cmp, fmt, mem::size_of};
 
-#[cfg(feature = "std")]
-use std;
-
 pub(crate) const DEGREE: usize = 8;
 
 /// Compute the BLAKE2sp hash of a slice of bytes all at once, using default
diff --git a/blake2/src/lib.rs b/blake2/src/lib.rs
index 269c6877f..9b2df1640 100644
--- a/blake2/src/lib.rs
+++ b/blake2/src/lib.rs
@@ -98,6 +98,7 @@
 //! [the BLAKE2 spec]: https://blake2.net/blake2.pdf
 
 #![no_std]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 #![doc(
     html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
     html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg"
@@ -109,15 +110,19 @@
 extern crate std;
 
 #[cfg(feature = "blake2b")]
+#[cfg_attr(docsrs, doc(cfg(feature = "blake2b")))]
 pub mod blake2b;
-
-#[cfg(feature = "blake2b")]
+#[cfg(all(feature = "blake2b", any(target_arch = "x86", target_arch = "x86_64")))]
+#[cfg_attr(docsrs, doc(cfg(feature = "blake2b")))]
+#[cfg_attr(docsrs, doc(cfg(any(target_arch = "x86", target_arch = "x86_64"))))]
 pub mod blake2bp;
 
 #[cfg(feature = "blake2s")]
+#[cfg_attr(docsrs, doc(cfg(feature = "blake2s")))]
 pub mod blake2s;
-
-#[cfg(feature = "blake2s")]
+#[cfg(all(feature = "blake2s", any(target_arch = "x86", target_arch = "x86_64")))]
+#[cfg_attr(docsrs, doc(cfg(feature = "blake2s")))]
+#[cfg_attr(docsrs, doc(cfg(any(target_arch = "x86", target_arch = "x86_64"))))]
 pub mod blake2sp;
 
 pub use crypto_mac;