Add GCC example for rpmsg echo

.github/workflows/gnu-toolchain.yml

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+name: GNU Toolchain CI
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ "**" ]
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: Build and Validate
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Show tool versions
+        run: |
+          make --version
+
+      - name: Restore toolchain cache
+        uses: actions/cache@v4
+        with:
+          path: |
+            $HOME/gnupru
+          key: toolchain-gnupru-2025.05.sha
+
+      - name: Install GNU toolchain if missing
+        run: |
+          set -e
+          mkdir -p "$HOME/gnupru/downloads"
+          cd "$HOME/gnupru"
+
+          # Install gnupru-2025.05
+          if [ ! -d "$HOME/gnupru/pru-elf-2025.05" ]; then
+            cd "$HOME/gnupru/downloads"
+            wget -q --retry-connrefused --waitretry=1 --tries=5 --timeout=30 \
+              https://github.com/dinuxbg/gnupru/releases/download/2025.05/pru-elf-2025.05.amd64.tar.xz
+            echo "23d4a8e8a64400ab73565be5575bc6ea5a3c1f5c06858a03b441e1549427380256ce7b22c3131f7b09d45e941ef133c5d51da38331cfaa338f6b601f21065a3e pru-elf-2025.05.amd64.tar.xz" > pru-elf-2025.05.amd64.sum
+            sha512sum -c pru-elf-2025.05.amd64.sum
+            cd "$HOME/gnupru"
+            tar xaf "$HOME/gnupru/downloads/pru-elf-2025.05.amd64.tar.xz"
+            mv pru-elf pru-elf-2025.05
+          fi
+
+          test -x "$HOME/gnupru/pru-elf-2025.05/bin/pru-gcc"
+
+      - name: Export toolchain environment
+        run: |
+          {
+            echo "PATH=$PATH:$HOME/gnupru/pru-elf-2025.05/bin"
+          } >> $GITHUB_ENV
+
+      - name: Build examples folder
+        run: |
+          make -C examples/gcc_rpmsg_echo_linux -j$(nproc) 
+          make -C examples/gcc_rpmsg_echo_linux -j$(nproc) MCU_DEVICE=am62x.pru1

examples/gcc_rpmsg_echo_linux/.gitignore

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+generated

examples/gcc_rpmsg_echo_linux/Makefile

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+# Copyright (c) 2026, Dimitar Dimitrov
+#   All rights reserved.
+#
+#   Redistribution and use in source and binary forms, with or without
+#   modification, are permitted provided that the following conditions are met:
+#
+#   * Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#   * Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in
+#     the documentation and/or other materials provided with the
+#     distribution.
+#   * Neither the name of the copyright holders nor the names of
+#     contributors may be used to endorse or promote products derived
+#     from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+
+# Very simple makefile to cross-compile for PRU using the GNU toolchain.
+
+# Select which PRU core to compile for
+MCU_DEVICE ?= am62x.pru0
+
+# Common flags
+CROSS_COMPILE ?= pru-
+CFLAGS += -Oz
+CFLAGS += -Wall -Wextra
+
+# Enable the GCC static analyzer.
+CFLAGS += -fanalyzer
+
+# Headers needed by the TI rpmsg library.
+HEADER_DIRS := \
+  ./ \
+  ../../source/include/linux
+
+
+CFLAGS += $(foreach directory, $(HEADER_DIRS), -I$(directory))
+
+# Define this to squeeze code size by removing atexit, exit, constructors
+# and destructors from CRT.
+CFLAGS += -minrt
+
+# Per-PRU core flags. The -mmcu option will select the correct linker
+# script and will predefine mcu-specific macros.
+CFLAGS += -mmcu=${MCU_DEVICE}
+
+# List of source files to compile for each PRU core.
+SRC := \
+    main.c \
+    ../../source/rpmsg/pru_rpmsg.c \
+    ../../source/rpmsg/pru_virtqueue.c
+
+# GCC's -MMD does not yield the needed C dependencies when compiling all
+# C source files at once. So manually list headers here.
+HEADERS := $(foreach directory, $(HEADER_DIRS), $(wildcard $(directory)/*.h))
+
+# Where to output compiled objects
+OUT := generated
+
+# Final ELF image file names
+ELF := $(OUT)/gcc_rpmsg_echo_linux_am62x-sk_${MCU_DEVICE}.elf
+
+# ============================ DO NOT TOUCH BELOW ============================
+all: $(ELF)
+	@echo Success: $^
+
+%.s : %.elf
+	$(CROSS_COMPILE)objdump -S -d $< > $@
+
+# Binary images for IMEM and DMEM memories. Might be useful
+# for firmware loaders that cannot handle ELF.
+%.imem.bin : %.elf
+	$(CROSS_COMPILE)objcopy -O binary  --only-section=.text* $< $@
+
+%.dmem.bin : %.elf
+	$(CROSS_COMPILE)objcopy -O binary              \
+	  --only-section=.data*                        \
+	  --only-section=.bss*                         \
+	  --set-section-flags .bss=alloc,load,contents \
+	  $< $@
+
+$(OUT):
+	mkdir $(OUT)
+
+$(ELF): $(SRC) $(HEADERS) | $(OUT)
+	$(CROSS_COMPILE)gcc $(CFLAGS) $(SRC) -o $@
+
+clean:
+	$(RM) -fr $(ELF) $(OUT)
+
+cscope:
+	cscope -bRk
+
+.PHONY: all clean cscope

examples/gcc_rpmsg_echo_linux/README.md

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+# RPMSG Echo Example Using the GNU Toolchain
+
+This is an RPMSG firmware built using the GNU toolchain for PRU. This firmware
+is the classical RPMSG echo example from Texas Instruments, but with a twist
+to show-off some GCC features. The returned echo string is reversed using
+inline assembly routine.
+
+WARNING: Neither the GNU PRU toolchain nor this example are supported by Texas Instruments!
+
+The example was last tested on BeaglePlay board running kernel 6.12.57-ti-arm64-r59.
+
+## Getting the GNU toolchain for PRU
+
+Convenient prebuilt toolchain binaries are offered [here](https://github.com/dinuxbg/gnupru/releases).
+They are prepared by the same hobbyist, who also maintains the PRU port for GCC and Binutils.
+This toolchain includes:
+  * [GCC](https://gcc.gnu.org/) compiler.
+  * [Binutils](https://www.gnu.org/software/binutils/) assembler, linker and tools.
+  * [newlib](https://sourceware.org/newlib/) C library.
+
+Being free software, the GNU toolchain can also be built from sources.
+PRU support has been mainlined, and is part of recent official source releases
+for GCC, Binutils and newlib. Apart from official GNU sources, you need only a
+[small additional package](https://github.com/dinuxbg/gnuprumcu) for
+SoC-specific support in order to
+[build the toolchain](https://github.com/dinuxbg/gnupru/?tab=readme-ov-file#building-from-sources) by yourself.
+
+## Compiling the example
+
+```
+cd examples/gcc_rpmsg_echo_linux
+make MCU_DEVICE=am62x.pru0
+```
+
+Or, if compiling for the other PRU core:
+
+```
+make MCU_DEVICE=am62x.pru1
+```
+
+Steps for running the firmware are the same as for the TI CGT example.
+
+## Reasons to consider using the GNU toolchain for PRU
+
+ * The GNU toolchain is free software.
+ * GCC supports the [latest language](https://gcc.gnu.org/onlinedocs/gcc/Standards.html#C-Language)
+   standards (e.g. C23 and C2Y), and numerous [extensions](https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html).
+ * GCC has a really nice [static analyzer](https://developers.redhat.com/articles/2025/04/10/6-usability-improvements-gcc-15#4__an_easier_transition_to_c23).
+ * GCC has a powerful [extension](https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html)
+   for writing snippets of inline assembly inside C functions.
+
+## Support
+
+For community support you can:
+  * File an issue in https://github.com/dinuxbg/gnupru
+  * Ask a question in https://forum.beagleboard.org

examples/gcc_rpmsg_echo_linux/config.h

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+
+/* These constants are excellently explained in examples/rpmsg_echo_linux/readme.md.
+ *
+ * Show-off here the GCC's "-mmcu=" option, which among other things
+ * automatically defines PRU-instance-specific macros (e.g. __AM62X_PRU0__).
+ * Thus instead of manually changing these constants in the Makefile
+ * as in the TI CGT example, we can simply define them in this header.
+ * An ifdef block is used for each supported PRU core instance.
+ *
+ *
+ * For a list of supported PRU core instances (a.k.a. MCUs), see
+ *   https://github.com/dinuxbg/gnuprumcu/blob/master/MCU-LIST.md
+ *
+ * For list of defined macros, simply open the correspondingly named
+ * spec file from the above project. Example:
+ *   https://github.com/dinuxbg/gnuprumcu/blob/master/device-specs/am62x.pru0
+ */
+#if defined(__AM62X_PRU0__)
+  #define HOST_INT_BIT 30
+  #define TO_ARM_HOST 16
+  #define FROM_ARM_HOST 17
+  #define CHAN_PORT 30
+  #define INTMAP_CHANNEL 0
+  #define INTMAP_HOST 0
+#elif defined(__AM62X_PRU1__)
+  #define HOST_INT_BIT 31
+  #define TO_ARM_HOST 18
+  #define FROM_ARM_HOST 19
+  #define CHAN_PORT 31
+  #define INTMAP_CHANNEL 1
+  #define INTMAP_HOST 1
+#else
+  #error "Please define the RPMSG channel properties for your specific PRU instance."
+#endif

examples/gcc_rpmsg_echo_linux/intc_map.h

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+#ifndef _INTC_MAP_H_
+#define _INTC_MAP_H_
+
+/*
+ * ======== PRU INTC Map ========
+ *
+ * Define the INTC mapping for interrupts going to the ICSS / ICSSG:
+ * 	ICSS Host interrupts 0, 1
+ * 	ICSSG Host interrupts 0, 1, 10-19
+ *
+ * Note that INTC interrupts going to the ARM Linux host should not be defined
+ * in this file (ICSS/ICSSG Host interrupts 2-9).
+ *
+ * The INTC configuration for interrupts going to the ARM host should be defined
+ * in the device tree node of the client driver, "interrupts" property.
+ * See Documentation/devicetree/bindings/interrupt-controller/ti,pruss-intc.yaml
+ * entry #interrupt-cells for more.
+ *
+ * For example, on ICSSG:
+ *
+ * &client_driver0 {
+ * 	interrupt-parent = <&icssg0_intc>;
+ * 	interrupts = <21 2 2>, <22 3 3>;
+ * 	interrupt-names = "interrupt_name1", "interrupt_name2";
+ * };
+ */
+
+#include <stddef.h>
+#include <rsc_types.h>
+#include "config.h"
+
+/*
+ * .pru_irq_map is used by the RemoteProc driver during initialization. However,
+ * the map is NOT used by the PRU firmware. The GNU linker's default script for PRU
+ * knows about the ".pru_irq_map", and will retain it.
+ */
+
+struct pru_irq_rsc my_irq_rsc
+__attribute__((section(".pru_irq_map"),unavailable("pru_irq_map is for usage by the host only"))) = {
+	0,			/* type = 0 */
+	1,			/* number of system events being mapped */
+	{
+		{FROM_ARM_HOST, INTMAP_CHANNEL, INTMAP_HOST},	/* {sysevt, channel, host interrupt} */
+	},
+};
+
+#endif /* _INTC_MAP_H_ */