MySensors gateway support for 64-bit OS on RPI (gcc cpu flags)

[frepkovsky]

Configure script does not support auto-configuration of gcc cpu flags for RPi SoCs on 64-bit OS (i.e. official Raspberry Pi OS). For all RPI SoCs detected, optimizations flags for floating point operations are added that are specific for 32-bit gcc only (for aarch32): "-mfpu=vfp -mfloat-abi=hard" and they do not exist in 64-bit gcc for aarch64. Running configuration on 64-bit OS on aarch64 results in error:

test@raspberrypi:~/MySensors $ ./configure --my-gateway=ethernet --my-port=5003 --my-is-rfm69hw --my-transport=rfm69 --my-rfm69-frequency=868
[SECTION] Detecting target machine.
  [OK] machine detected: SoC=BCM2837, Type=rpi3, CPU=aarch64.
[SECTION] Detecting SPI driver.
  [OK] SPI driver detected:BCM.
[SECTION] Gateway configuration.
  [OK] Type: ethernet.
  [OK] Transport: rfm69.
  [OK] Signing: Disabled.
  [OK] Encryption: Disabled.
  [OK] CPPFLAGS: -march=armv8-a+crc -mtune=cortex-a53 -mfpu=neon-fp-armv8 -mfloat-abi=hard -DMY_RADIO_RFM69 -DMY_RFM69_NEW_DRIVER -DMY_GATEWAY_LINUX -DMY_DEBUG -DLINUX_SPI_BCM -DLINUX_ARCH_RASPBERRYPI -DMY_RFM69_FREQUENCY=RFM69_868MHZ -DMY_IS_RFM69HW -DMY_PORT=5003 
  [OK] CXXFLAGS:  -std=c++11
[SECTION] Detecting init system.
  [OK] Init system detected: systemd.
[SECTION] Saving configuration.
  [OK] Saved.
[SECTION] Cleaning previous builds.
  [OK] Finished.

test@raspberrypi:~/MySensors $ make
gcc -MT build/hal/architecture/Linux/drivers/core/config.o -MMD -MP -march=armv8-a+crc -mtune=cortex-a53 -mfpu=neon-fp-armv8 -mfloat-abi=hard -DMY_RADIO_RFM69 -DMY_RFM69_NEW_DRIVER -DMY_GATEWAY_LINUX -DMY_DEBUG -DLINUX_SPI_BCM -DLINUX_ARCH_RASPBERRYPI -DMY_RFM69_FREQUENCY=RFM69_868MHZ -DMY_IS_RFM69HW -DMY_PORT=5003  -Ofast -g -Wall -Wextra  -I. -I./core -I./hal/architecture/Linux/drivers/core -I./hal/architecture/Linux/drivers/BCM -c hal/architecture/Linux/drivers/core/config.c -o build/hal/architecture/Linux/drivers/core/config.o
gcc: error: unrecognized command-line option ‘-mfpu=neon-fp-armv8’
gcc: error: unrecognized command-line option ‘-mfloat-abi=hard’
make: *** [Makefile:103: build/hal/architecture/Linux/drivers/core/config.o] Error 1

Function gcc_cpu_flags() in configure script needs to be updated to avoid using flags "-mfpu=vfp -mfloat-abi=hard" on aarch64 (fp and simd are enabled by default for all current aarch64 architectures).

function gcc_cpu_flags {
    local soc=$1
    case $soc in
    BCM2835)
        flags="-march=armv6zk -mtune=arm1176jzf-s -mfpu=vfp -mfloat-abi=hard"
        ;;
    BCM2836)
        flags="-march=armv7-a -mtune=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard"
        ;;
    BCM2837)
        flags="-march=armv8-a+crc -mtune=cortex-a53 -mfpu=neon-fp-armv8 -mfloat-abi=hard
        ;;
    BCM2711)
        flags="-march=armv8-a+crc -mtune=cortex-a72 -mfpu=neon-fp-armv8 -mfloat-abi=hard"
        ;;
    AM33XX)
        flags="-march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=hard"
        ;;
    A10)
        flags="-march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=hard"
        ;;
    A13)
        flags="-march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=hard"
        ;;
    A20)
        flags="-march=armv7-a -mtune=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard"
        ;;
    H3)
        flags="-march=armv7-a -mtune=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard"
        ;;
    RK3399)
        flags="-march=armv8-a+crc+crypto -mtune=cortex-a72.cortex-a53 -mfix-cortex-a53-835769 -mfix-cortex-a53-843419"
        ;;
    *)
        flags=""
    esac
    echo ${flags}
}