ARM: vf610: enable Cortex-M4 configuration on Vybrid SoC

This patch allows to build the Kernel for Vybrid (VF6xx) SoC
when ARMv7-M CPU is selected. The resulting image runs on the
secondary Cortex-M4 core. This core has equally access to all
peripherals as the main Cortex-A5 core. However, there is no
resource control mechanism, hence when both cores are used
simultaneously, orthogonal device tree's are required.

The boot CPU is dependent on the SoC variant. The available
boards use mostly variants where the Cortex-A5 is the primary
and hence the boot CPU. Booting the secondary Cortex-M4 CPU
needs SoC specific registers written. There is no in kernel
support for this right now, a external userspace utility
called "m4boot" can be used to boot the kernel:

m4boot xipImage initramfs.cpio.lzo vf610m4-colibri.dtb

Signed-off-by: Stefan Agner <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>

Documentation/devicetree/bindings/arm/fsl.txt

···
 For the Vybrid SoC familiy all variants with DDR controller are supported,
 which is the VF5xx and VF6xx series. Out of historical reasons, in most
 places the kernel uses vf610 to refer to the whole familiy.
+The compatible string "fsl,vf610m4" is used for the secondary Cortex-M4
+core support.
 
 Required root node compatible property (one of them):
     - compatible = "fsl,vf500";
     - compatible = "fsl,vf510";
     - compatible = "fsl,vf600";
     - compatible = "fsl,vf610";
+    - compatible = "fsl,vf610m4";
 
 Freescale LS1021A Platform Device Tree Bindings
 ------------------------------------------------

arch/arm/mach-imx/Kconfig

···
 menuconfig ARCH_MXC
-	bool "Freescale i.MX family" if ARCH_MULTI_V4_V5 || ARCH_MULTI_V6_V7
+	bool "Freescale i.MX family" if ARCH_MULTI_V4_V5 || ARCH_MULTI_V6_V7 || ARM_SINGLE_ARMV7M
 	select ARCH_REQUIRE_GPIOLIB
 	select ARM_CPU_SUSPEND if PM
 	select CLKSRC_MMIO
···
 
 endif
 
-if ARCH_MULTI_V5
-
 comment "Device tree only"
+
+if ARCH_MULTI_V5
 
 config SOC_IMX25
 	bool "i.MX25 support"
···
 
 if ARCH_MULTI_V7
 
-comment "Device tree only"
+comment "Cortex-A platforms"
 
 config SOC_IMX5
 	bool
···
 	help
 	  This enables support for Freescale i.MX6 SoloX processor.
 
+config SOC_LS1021A
+	bool "Freescale LS1021A support"
+	select ARM_GIC
+	select HAVE_ARM_ARCH_TIMER
+	select PCI_DOMAINS if PCI
+	select ZONE_DMA if ARM_LPAE
+	help
+	  This enables support for Freescale LS1021A processor.
+
+endif
+
+comment "Cortex-A/Cortex-M asymmetric multiprocessing platforms"
+
+if ARCH_MULTI_V7 || ARM_SINGLE_ARMV7M
+
 config SOC_VF610
 	bool "Vybrid Family VF610 support"
-	select IRQ_DOMAIN_HIERARCHY
-	select ARM_GIC
+	select ARM_GIC if ARCH_MULTI_V7
 	select PINCTRL_VF610
 	select PL310_ERRATA_769419 if CACHE_L2X0
 	select SMP_ON_UP if SMP
···
 	default VF_USE_ARM_GLOBAL_TIMER
 
 	config VF_USE_ARM_GLOBAL_TIMER
-		bool "Use ARM Global Timer"
+		bool "Use ARM Global Timer" if ARCH_MULTI_V7
 		select ARM_GLOBAL_TIMER
 		select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 		help
···
 		  Use SoC Periodic Interrupt Timer (PIT) as clocksource
 
 endchoice
-
-config SOC_LS1021A
-	bool "Freescale LS1021A support"
-	select ARM_GIC
-	select HAVE_ARM_ARCH_TIMER
-	select PCI_DOMAINS if PCI
-	select ZONE_DMA if ARM_LPAE
-
-	help
-	  This enables support for Freescale LS1021A processor.
 
 endif
 

arch/arm/mach-imx/mach-vf610.c

···
 	"fsl,vf510",
 	"fsl,vf600",
 	"fsl,vf610",
+	"fsl,vf610m4",
 	NULL,
 };