kernel: only optimized for size if small_flash

Add a new config option to allow to select the default compile
optimization level for the kernel.

Select the optimization for size by default if the small_flash feature is
set. Otherwise "Optimize for performance" is set.

Add the small_flash feature flag to all (sub)targets which had the
optimization for size in their default kernel config.

Remove CC_OPTIMIZE_FOR_* symbols from all kernel configs to apply the new
setting.

Exceptions to the above are:

  - lantiq, where the optimization for size is only required for the
    xway_legacy subtarget but was set for the whole target
  - mediatek, ramips/mt7620 & ramips/mt76x8 where boards should have
    plenty of space and an optimization for size doesn't make much sense
  - rb532, which has 128MByte flash

Signed-off-by: Mathias Kresin <dev@kresin.me>

config/Config-kernel.in

@@ -806,3 +806,25 @@ config KERNEL_DEVKMEM
 	  Say Y here if you want to support the /dev/kmem device. The
 	  /dev/kmem device is rarely used, but can be used for certain
 	  kind of kernel debugging operations.
+
+#
+# compile optimiziation setting
+#
+choice
+	prompt "Compiler optimization level"
+	default KERNEL_CC_OPTIMIZE_FOR_SIZE if SMALL_FLASH
+
+config KERNEL_CC_OPTIMIZE_FOR_PERFORMANCE
+	bool "Optimize for performance"
+	help
+	  This is the default optimization level for the kernel, building
+	  with the "-O2" compiler flag for best performance and most
+	  helpful compile-time warnings.
+
+config KERNEL_CC_OPTIMIZE_FOR_SIZE
+	bool "Optimize for size"
+	help
+	  Enabling this option will pass "-Os" instead of "-O2" to
+	  your compiler resulting in a smaller kernel.
+
+endchoice

target/linux/adm5120/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 BOARD:=adm5120
 BOARDNAME:=Infineon/ADMtek ADM5120
-FEATURES:=low_mem source-only
+FEATURES:=low_mem small_flash source-only
 SUBTARGETS:=router_le router_be rb1xx
 INITRAMFS_EXTRA_FILES:=
 

target/linux/adm5120/config-3.18

@@ -45,7 +45,6 @@ CONFIG_ARCH_SUSPEND_POSSIBLE=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
 CONFIG_ARM_AMBA=y
 CONFIG_BUILD_BIN2C=y
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_CMDLINE="console=ttyAM0,115200 rootfstype=squashfs,jffs2"

target/linux/at91/config-4.9

@@ -58,8 +58,6 @@ CONFIG_BLK_DEV_SD=y
 # CONFIG_BPF_SYSCALL is not set
 # CONFIG_BRIDGE is not set
 CONFIG_CACHE_L2X0=y
-CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y
-# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
 CONFIG_CLKDEV_LOOKUP=y
 CONFIG_CLKSRC_OF=y
 CONFIG_CLKSRC_PROBE=y

target/linux/ath79/tiny/config-default

@@ -1,5 +1,3 @@
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_BLK_MQ_PCI=y
 CONFIG_LEDS_RESET=y
 CONFIG_OF_ADDRESS_PCI=y

target/linux/au1000/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 ARCH:=mipsel
 BOARD:=au1000
 BOARDNAME:=RMI/AMD AU1x00
-FEATURES:=squashfs usb pci source-only
+FEATURES:=squashfs usb pci small_flash source-only
 SUBTARGETS:=au1500 au1550
 MAINTAINER:=Florian Fainelli <florian@openwrt.org>
 

target/linux/au1000/config-3.18

@@ -11,7 +11,6 @@ CONFIG_ARCH_PHYS_ADDR_T_64BIT=y
 CONFIG_ARCH_REQUIRE_GPIOLIB=y
 CONFIG_ARCH_SUSPEND_POSSIBLE=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_CMDLINE="console=ttyS0,115200 root=/dev/mtdblock0 rootfstype=squashfs,jffs2"

target/linux/generic/config-3.18

@@ -580,7 +580,6 @@ CONFIG_CAVIUM_OCTEON_HELPER=y
 # CONFIG_CAVIUM_OCTEON_SIMULATOR is not set
 # CONFIG_CAVIUM_OCTEON_SOC is not set
 # CONFIG_CB710_CORE is not set
-# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
 # CONFIG_CC_STACKPROTECTOR is not set
 CONFIG_CC_STACKPROTECTOR_NONE=y
 # CONFIG_CC_STACKPROTECTOR_REGULAR is not set

target/linux/generic/config-4.14

@@ -717,8 +717,6 @@ CONFIG_CARDBUS=y
 # CONFIG_CB710_CORE is not set
 # CONFIG_CC10001_ADC is not set
 # CONFIG_CCS811 is not set
-CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y
-# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
 # CONFIG_CC_STACKPROTECTOR is not set
 CONFIG_CC_STACKPROTECTOR_NONE=y
 # CONFIG_CC_STACKPROTECTOR_REGULAR is not set

target/linux/generic/config-4.9

@@ -680,8 +680,6 @@ CONFIG_CARDBUS=y
 # CONFIG_CAVIUM_OCTEON_SOC is not set
 # CONFIG_CB710_CORE is not set
 # CONFIG_CC10001_ADC is not set
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 # CONFIG_CC_STACKPROTECTOR is not set
 CONFIG_CC_STACKPROTECTOR_NONE=y
 # CONFIG_CC_STACKPROTECTOR_REGULAR is not set

target/linux/lantiq/config-4.14

@@ -20,8 +20,6 @@ CONFIG_ARCH_USE_BUILTIN_BSWAP=y
 CONFIG_ARCH_USE_QUEUED_RWLOCKS=y
 CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CLKDEV_LOOKUP=y
 CONFIG_CLONE_BACKWARDS=y

target/linux/layerscape/armv8_32b/config-4.9

@@ -145,8 +145,6 @@ CONFIG_CAN_RAW=y
 # CONFIG_CAN_SJA1000 is not set
 # CONFIG_CAN_SOFTING is not set
 # CONFIG_CAN_TI_HECC is not set
-CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y
-# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
 # CONFIG_CFS_BANDWIDTH is not set
 CONFIG_CGROUPS=y
 CONFIG_CGROUP_CPUACCT=y

target/linux/layerscape/armv8_64b/config-4.9

@@ -156,8 +156,6 @@ CONFIG_CAVIUM_ERRATUM_22375=y
 CONFIG_CAVIUM_ERRATUM_23144=y
 CONFIG_CAVIUM_ERRATUM_23154=y
 CONFIG_CAVIUM_ERRATUM_27456=y
-CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y
-# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
 CONFIG_CEPH_LIB=y
 # CONFIG_CEPH_LIB_PRETTYDEBUG is not set
 # CONFIG_CEPH_LIB_USE_DNS_RESOLVER is not set

target/linux/mcs814x/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 ARCH:=arm
 BOARD:=mcs814x
 BOARDNAME:=Moschip MCS814x
-FEATURES:=usb squashfs low_mem source-only
+FEATURES:=usb squashfs low_mem small_flash source-only
 CPU_TYPE:=arm926ej-s
 MAINTAINER:=Florian Fainelli <florian@openwrt.org>
 

target/linux/mcs814x/config-3.18

@@ -26,7 +26,6 @@ CONFIG_ARM_L1_CACHE_SHIFT=5
 # CONFIG_ARM_THUMB is not set
 CONFIG_BINFMT_MISC=y
 # CONFIG_CACHE_L2X0 is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CLKDEV_LOOKUP=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_CMDLINE="earlyprintk"

target/linux/mediatek/mt7622/config-4.14

@@ -88,8 +88,6 @@ CONFIG_BT_HCIUART=y
 CONFIG_BT_HCIUART_SERDEV=y
 CONFIG_BT_HCIVHCI=y
 CONFIG_BUILD_BIN2C=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CLKDEV_LOOKUP=y
 CONFIG_CLKSRC_MMIO=y
 CONFIG_CLOCK_THERMAL=y

target/linux/ppc40x/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 ARCH:=powerpc
 BOARD:=ppc40x
 BOARDNAME:=AMCC/IBM PPC40x
-FEATURES:=squashfs broken
+FEATURES:=squashfs small_flash broken
 CPU_TYPE:=405
 MAINTAINER:=Imre Kaloz <kaloz@openwrt.org>
 

target/linux/ppc40x/config-3.18

@@ -27,7 +27,6 @@ CONFIG_ARCH_WANT_OPTIONAL_GPIOLIB=y
 CONFIG_AUDIT_ARCH=y
 CONFIG_BOOKE_WDT=y
 CONFIG_BOUNCE=y
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_CMDLINE="console=ttyS0,115200 rootfstype=squashfs,jffs2 noinitrd"
 CONFIG_CMDLINE_BOOL=y

target/linux/ppc44x/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 ARCH:=powerpc
 BOARD:=ppc44x
 BOARDNAME:=AMCC/IBM PPC44x
-FEATURES:=squashfs broken
+FEATURES:=squashfs small_flash broken
 CPU_TYPE:=440
 MAINTAINER:=Imre Kaloz <kaloz@openwrt.org>
 

target/linux/ppc44x/config-3.18

@@ -34,7 +34,6 @@ CONFIG_BOOKE=y
 CONFIG_BOOKE_WDT=y
 CONFIG_BOUNCE=y
 CONFIG_CANYONLANDS=y
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_CMDLINE="console=ttyS0,115200 root=/dev/mtdblock1 rootfstype=squashfs,jffs2 noinitrd"
 CONFIG_CMDLINE_BOOL=y

target/linux/ramips/mt7620/config-4.14

@@ -22,8 +22,6 @@ CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
 CONFIG_AT803X_PHY=y
 CONFIG_BLK_MQ_PCI=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CEVT_SYSTICK_QUIRK=y
 CONFIG_CLKDEV_LOOKUP=y

target/linux/ramips/mt76x8/config-4.14

@@ -22,8 +22,6 @@ CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
 CONFIG_AT803X_PHY=y
 CONFIG_BLK_MQ_PCI=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CEVT_SYSTICK_QUIRK=y
 CONFIG_CLKDEV_LOOKUP=y

target/linux/ramips/rt288x/config-4.14

@@ -21,8 +21,6 @@ CONFIG_ARCH_USE_QUEUED_RWLOCKS=y
 CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
 CONFIG_BLK_MQ_PCI=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 # CONFIG_CEVT_SYSTICK_QUIRK is not set
 CONFIG_CLKDEV_LOOKUP=y

target/linux/ramips/rt288x/target.mk

@@ -4,6 +4,7 @@
 
 SUBTARGET:=rt288x
 BOARDNAME:=RT288x based boards
+FEATURES+=small_flash
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES += kmod-rt2800-soc wpad-mini

target/linux/ramips/rt305x/config-4.14

@@ -12,8 +12,6 @@ CONFIG_ARCH_SUPPORTS_UPROBES=y
 CONFIG_ARCH_SUSPEND_POSSIBLE=y
 CONFIG_ARCH_USE_BUILTIN_BSWAP=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CEVT_SYSTICK_QUIRK=y
 CONFIG_CLKDEV_LOOKUP=y

target/linux/ramips/rt305x/target.mk

@@ -4,7 +4,7 @@
 
 SUBTARGET:=rt305x
 BOARDNAME:=RT3x5x/RT5350 based boards
-FEATURES+=usb ramdisk
+FEATURES+=usb ramdisk small_flash
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES += kmod-rt2800-soc wpad-mini

target/linux/ramips/rt3883/config-4.14

@@ -22,8 +22,6 @@ CONFIG_ARCH_USE_QUEUED_RWLOCKS=y
 CONFIG_ARCH_USE_QUEUED_SPINLOCKS=y
 CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
 CONFIG_BLK_MQ_PCI=y
-# CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE is not set
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 # CONFIG_CEVT_SYSTICK_QUIRK is not set
 CONFIG_CLKDEV_LOOKUP=y

target/linux/ramips/rt3883/target.mk

@@ -4,7 +4,7 @@
 
 SUBTARGET:=rt3883
 BOARDNAME:=RT3662/RT3883 based boards
-FEATURES+=usb pci
+FEATURES+=usb pci small_flash
 CPU_TYPE:=74kc
 
 DEFAULT_PACKAGES += kmod-rt2800-pci kmod-rt2800-soc wpad-mini

target/linux/rb532/config-4.9

@@ -16,7 +16,6 @@ CONFIG_ARCH_WANT_IPC_PARSE_VERSION=y
 CONFIG_ATA=y
 CONFIG_BLK_DEV_LOOP=y
 CONFIG_BLK_DEV_SD=y
-CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 CONFIG_CEVT_R4K=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_CPU_GENERIC_DUMP_TLB=y