From de392969ce2e6a6c0a3d358b9aa1474a3d8f71a8 Mon Sep 17 00:00:00 2001
From: Rodrigo Valle <rdan.valle@gmail.com>
Date: Thu, 17 Sep 2020 01:05:10 -0700
Subject: [PATCH] Add Makefile targets to program MCU

Also include the codgen-units=1 workaround for a rustc segfault when building
this crate in release mode. Some details here:

https://github.com/rust-lang/rust/issues/62896
---
 Cargo.toml                      |  6 ++++++
 Makefile                        | 30 ++++++++++++++++++++++++++++++
 README.md                       |  2 --
 avr-unknown-gnu-atmega2560.json |  6 ++++--
 4 files changed, 40 insertions(+), 4 deletions(-)
 create mode 100644 Makefile
 delete mode 100644 README.md

diff --git a/Cargo.toml b/Cargo.toml
index 46eaddc..f0f132e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,3 +7,9 @@ edition = "2018"
 [dependencies]
 # this is broken
 #ruduino = "0.2"
+
+[profile.release]
+codegen-units = 1
+lto = true
+debug = false
+opt-level = "s"
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..152e079
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,30 @@
+.PHONY: upload
+
+BIN=rust-test
+DEVICE=/dev/ttyUSB0
+RELEASE_DIR=target/avr-unknown-gnu-atmega2560/release
+ELF=$(RELEASE_DIR)/$(BIN).elf
+HEX=$(RELEASE_DIR)/$(BIN).hex
+EEP=$(RELEASE_DIR)/$(BIN).eep
+SRC=$(wildcard **/*.rs)
+
+build: $(HEX)
+
+upload: $(HEX)
+	avrdude -patmega2560 -cwiring -P$(DEVICE) -b115200 -D -Uflash:w:$(HEX):i
+
+# rust builds a .elf file
+$(ELF): $(SRC)
+	cargo build --release
+
+# convert elf to hex for the programmer, pull .eeprom out because that is
+# programmed separately
+# ihex is short for "intel hex", which is recognized by avrdude
+$(HEX): $(ELF)
+	avr-objcopy -O ihex -R .eeprom $(ELF) $(HEX)
+
+# pull .eeprom from the elf and create a separate file representing what should
+# be written to the eeprom (this file is currently unused in the build process)
+# eeprom can also be programmed by avrdude's -U
+$(EEP): $(ELF)
+	avr-objcopy -O ihex -j .eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0 $(ELF) $(EEP)
diff --git a/README.md b/README.md
deleted file mode 100644
index fee29b1..0000000
--- a/README.md
+++ /dev/null
@@ -1,2 +0,0 @@
-basically atmega2560.json is required to be the name because of a bug with
-relative paths in dylanmckay/target-cpu-utils
diff --git a/avr-unknown-gnu-atmega2560.json b/avr-unknown-gnu-atmega2560.json
index 98a18c1..4041977 100644
--- a/avr-unknown-gnu-atmega2560.json
+++ b/avr-unknown-gnu-atmega2560.json
@@ -11,7 +11,8 @@
   "late-link-args": {
       "gcc": [
           "-lgcc",
-          "-lc"
+          "-lc",
+          "-flto"
       ]
   },
   "linker": "avr-gcc",
@@ -24,7 +25,8 @@
   "pre-link-args": {
     "gcc": [
       "-mmcu=atmega2560",
-      "-Wl,--as-needed"
+      "-Wl,--as-needed",
+      "-Wl,--gc-sections"
     ]
   },
   "target-c-int-width": "16",