ARM: let CPUs not being able to run in ARM mode enter in THUMB mode
Some ARM cores are not capable to run in ARM mode (e.g. Cortex-M3). So
obviously these cannot enter the kernel in ARM mode. Make an exception
for them and let them enter in THUMB mode.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Message-Id: 1358162123-30113-1-git-send-email-u.kleine-koenig@pengutronix.de
Acked-by: Nicolas Pitre <nico@linaro.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 67874b8..e04c779 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1656,8 +1656,9 @@
default 100
config THUMB2_KERNEL
- bool "Compile the kernel in Thumb-2 mode"
+ bool "Compile the kernel in Thumb-2 mode" if !CPU_THUMBONLY
depends on CPU_V7 && !CPU_V6 && !CPU_V6K
+ default y if CPU_THUMBONLY
select AEABI
select ARM_ASM_UNIFIED
select ARM_UNWIND
diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S
index 2c228a0..6a2e09c 100644
--- a/arch/arm/kernel/head-nommu.S
+++ b/arch/arm/kernel/head-nommu.S
@@ -32,15 +32,21 @@
* numbers for r1.
*
*/
- .arm
__HEAD
+
+#ifdef CONFIG_CPU_THUMBONLY
+ .thumb
+ENTRY(stext)
+#else
+ .arm
ENTRY(stext)
THUMB( adr r9, BSYM(1f) ) @ Kernel is always entered in ARM.
THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
THUMB( .thumb ) @ switch to Thumb now.
THUMB(1: )
+#endif
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
@ and irqs disabled
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 3fd629d..8defd63 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -397,6 +397,13 @@
select CPU_PABRT_V7
select CPU_TLB_V7 if MMU
+config CPU_THUMBONLY
+ bool
+ # There are no CPUs available with MMU that don't implement an ARM ISA:
+ depends on !MMU
+ help
+ Select this if your CPU doesn't support the 32 bit ARM instructions.
+
# Figure out what processor architecture version we should be using.
# This defines the compiler instruction set which depends on the machine type.
config CPU_32v3
@@ -608,7 +615,7 @@
bool
config ARM_THUMB
- bool "Support Thumb user binaries"
+ bool "Support Thumb user binaries" if !CPU_THUMBONLY
depends on CPU_ARM720T || CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || CPU_ARM1020 || CPU_ARM1020E || CPU_ARM1022 || CPU_ARM1026 || CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_V6 || CPU_V6K || CPU_V7 || CPU_FEROCEON
default y
help