From 137ba15e6ef31534a2002a02e69b774232f0b040 Mon Sep 17 00:00:00 2001
From: Christian Marangi <ansuelsmth@gmail.com>
Date: Tue, 4 Oct 2022 18:43:38 +0200
Subject: [PATCH] CI: kernel: use ccache to speedup workflow

Use ccache to speedup kernel compilation.
Ccache dir is cached across each build test. To refresh ccache directory
we generate an hash of the kernel include files, that includes the
kernel versions of every kernel supported and the kernel compile
includes.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 .github/workflows/kernel.yml | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/.github/workflows/kernel.yml b/.github/workflows/kernel.yml
index 6c8ad68438..0ba8c27e2e 100644
--- a/.github/workflows/kernel.yml
+++ b/.github/workflows/kernel.yml
@@ -18,6 +18,7 @@ jobs:
     outputs:
       target: ${{ steps.find_targets.outputs.target }}
       owner_lc: ${{ steps.lower_owner.outputs.owner_lc }}
+      ccache_hash: ${{ steps.ccache_hash.outputs.ccache_hash }}
 
     steps:
       - name: Checkout
@@ -30,6 +31,13 @@ jobs:
             | tr '[:upper:]' '[:lower:]')
           echo "::set-output name=owner_lc::$OWNER_LC"
 
+      - name: Generate ccache hash
+        id: ccache_hash
+        run: |
+          CCACHE_HASH=$(md5sum include/kernel-* | awk '{ print $1 }' \
+           | md5sum | awk '{ print $1 }')
+          echo "::set-output name=ccache_hash::$CCACHE_HASH"
+
       - name: Set targets
         id: find_targets
         run: |
@@ -133,6 +141,14 @@ jobs:
           path: openwrt/${{ env.TOOLCHAIN_FILE }}
           key: ${{ env.TOOLCHAIN_FILE }}-${{ env.TOOLCHAIN_SHA256 }}
 
+      - name: Cache ccache
+        uses: actions/cache@v3
+        with:
+          path: openwrt/.ccache
+          key: ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-${{ needs.determine_targets.outputs.ccache_hash }}
+          restore-keys: |
+            ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-
+
       - name: Download external toolchain
         if: ${{ steps.cache-external-toolchain.outputs.cache-hit != 'true' }}
         shell: su buildbot -c "sh -e {0}"
@@ -153,6 +169,7 @@ jobs:
           echo CONFIG_ALL_KMODS=y >> .config
           echo CONFIG_DEVEL=y >> .config
           echo CONFIG_AUTOREMOVE=y >> .config
+          echo CONFIG_CCACHE=y >> .config
 
           ./scripts/ext-toolchain.sh \
             --toolchain ${{ env.TOOLCHAIN_FILE }}/toolchain-* \