From feb229ddd5befd9fdb6fa873458db502d722e82c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert=20J=C3=B6rdens?= <rj@quartiq.de>
Date: Mon, 30 Nov 2020 12:02:14 +0100
Subject: [PATCH] cargo: add docs for target cpu/features

---
 .cargo/config | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/.cargo/config b/.cargo/config
index 9968846..ea1d6c0 100644
--- a/.cargo/config
+++ b/.cargo/config
@@ -2,8 +2,14 @@
 runner = "gdb-multiarch -q -x openocd.gdb"
 rustflags = [
     "-C", "link-arg=-Tlink.x",
+# The target (below) defaults to cortex-m4
+# There currently are two different options to go beyond that:
+# 1. cortex-m7 has the right flags and instructions (FPU) but no instruction schedule yet
     "-C", "target-cpu=cortex-m7",
+# 2. cortex-m4 with the additional fpv5 instructions and a potentially
+# better-than-nothing instruction schedule
     "-C", "target-feature=+fp-armv8d16",
+# When combined they are equivalent to (1) alone
 ]
 
 [build]