ARM: Add ARMv7-M support

Signed-off-by: Kamil Lulko <rev13@wp.pl>

5 files changed, 201 insertions, 2 deletions

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index da8ed72a11..0e1ad0e3dd 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -8,7 +8,9 @@
 lib-$(CONFIG_USE_PRIVATE_LIBGCC) += _ashldi3.o _ashrdi3.o _divsi3.o \
 			_lshrdi3.o _modsi3.o _udivsi3.o _umodsi3.o div0.o
 
-ifdef CONFIG_ARM64
+ifdef CONFIG_CPU_V7M
+obj-y	+= vectors_m.o crt0.o
+else ifdef CONFIG_ARM64
 obj-y	+= crt0_64.o
 else
 obj-y	+= vectors.o crt0.o
@@ -36,7 +38,9 @@ obj-$(CONFIG_SEMIHOSTING) += semihosting.o
 
 obj-y	+= sections.o
 obj-y	+= stack.o
-ifdef CONFIG_ARM64
+ifdef CONFIG_CPU_V7M
+obj-y	+= interrupts_m.o
+else ifdef CONFIG_ARM64
 obj-y	+= gic_64.o
 obj-y	+= interrupts_64.o
 else
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index 92d37324d3..afd4f102dc 100644
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -9,6 +9,9 @@
 #include <config.h>
 #include <asm-offsets.h>
 #include <linux/linkage.h>
+#ifdef CONFIG_CPU_V7M
+#include <asm/armv7m.h>
+#endif
 
 /*
  * This file handles the target-independent stages of the U-Boot
@@ -66,15 +69,30 @@ ENTRY(_main)
 #else
 	ldr	sp, =(CONFIG_SYS_INIT_SP_ADDR)
 #endif
+#if defined(CONFIG_CPU_V7M)	/* v7M forbids using SP as BIC destination */
+	mov	r3, sp
+	bic	r3, r3, #7
+	mov	sp, r3
+#else
 	bic	sp, sp, #7	/* 8-byte alignment for ABI compliance */
+#endif
 	mov	r2, sp
 	sub	sp, sp, #GD_SIZE	/* allocate one GD above SP */
+#if defined(CONFIG_CPU_V7M)	/* v7M forbids using SP as BIC destination */
+	mov	r3, sp
+	bic	r3, r3, #7
+	mov	sp, r3
+#else
 	bic	sp, sp, #7	/* 8-byte alignment for ABI compliance */
+#endif
 	mov	r9, sp		/* GD is above SP */
 	mov	r1, sp
 	mov	r0, #0
 clr_gd:
 	cmp	r1, r2			/* while not at end of GD */
+#if defined(CONFIG_CPU_V7M)
+	itt	lo
+#endif
 	strlo	r0, [r1]		/* clear 32-bit GD word */
 	addlo	r1, r1, #4		/* move to next */
 	blo	clr_gd
@@ -94,13 +112,22 @@ clr_gd:
  */
 
 	ldr	sp, [r9, #GD_START_ADDR_SP]	/* sp = gd->start_addr_sp */
+#if defined(CONFIG_CPU_V7M)	/* v7M forbids using SP as BIC destination */
+	mov	r3, sp
+	bic	r3, r3, #7
+	mov	sp, r3
+#else
 	bic	sp, sp, #7	/* 8-byte alignment for ABI compliance */
+#endif
 	ldr	r9, [r9, #GD_BD]		/* r9 = gd->bd */
 	sub	r9, r9, #GD_SIZE		/* new GD is below bd */
 
 	adr	lr, here
 	ldr	r0, [r9, #GD_RELOC_OFF]		/* r0 = gd->reloc_off */
 	add	lr, lr, r0
+#if defined(CONFIG_CPU_V7M)
+	orr	lr, #1				/* As required by Thumb-only */
+#endif
 	ldr	r0, [r9, #GD_RELOCADDR]		/* r0 = gd->relocaddr */
 	b	relocate_code
 here:
@@ -134,6 +161,9 @@ here:
 	mov	r2, #0x00000000		/* prepare zero to clear BSS */
 
 clbss_l:cmp	r0, r1			/* while not at end of BSS */
+#if defined(CONFIG_CPU_V7M)
+	itt	lo
+#endif
 	strlo	r2, [r0]		/* clear 32-bit BSS word */
 	addlo	r0, r0, #4		/* move to next */
 	blo	clbss_l
diff --git a/arch/arm/lib/interrupts_m.c b/arch/arm/lib/interrupts_m.c
new file mode 100644
index 0000000000..89ce493861
--- /dev/null
+++ b/arch/arm/lib/interrupts_m.c
@@ -0,0 +1,95 @@
+/*
+ * (C) Copyright 2015
+ * Kamil Lulko, <rev13@wp.pl>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+
+/*
+ * Upon exception entry ARMv7-M processors automatically save stack
+ * frames containing some registers. For simplicity initial
+ * implementation uses only this auto-saved stack frame.
+ * This does not contain complete register set dump,
+ * only R0-R3, R12, LR, PC and xPSR are saved.
+ */
+
+struct autosave_regs {
+	long uregs[8];
+};
+
+#define ARM_XPSR	uregs[7]
+#define ARM_PC		uregs[6]
+#define ARM_LR		uregs[5]
+#define ARM_R12		uregs[4]
+#define ARM_R3		uregs[3]
+#define ARM_R2		uregs[2]
+#define ARM_R1		uregs[1]
+#define ARM_R0		uregs[0]
+
+int interrupt_init(void)
+{
+	return 0;
+}
+
+void enable_interrupts(void)
+{
+	return;
+}
+
+int disable_interrupts(void)
+{
+	return 0;
+}
+
+void dump_regs(struct autosave_regs *regs)
+{
+	printf("pc : %08lx    lr : %08lx    xPSR : %08lx\n",
+	       regs->ARM_PC, regs->ARM_LR, regs->ARM_XPSR);
+	printf("r12 : %08lx   r3 : %08lx    r2 : %08lx\n"
+		"r1 : %08lx    r0 : %08lx\n",
+		regs->ARM_R12, regs->ARM_R3, regs->ARM_R2,
+		regs->ARM_R1, regs->ARM_R0);
+}
+
+void bad_mode(void)
+{
+	panic("Resetting CPU ...\n");
+	reset_cpu(0);
+}
+
+void do_hard_fault(struct autosave_regs *autosave_regs)
+{
+	printf("Hard fault\n");
+	dump_regs(autosave_regs);
+	bad_mode();
+}
+
+void do_mm_fault(struct autosave_regs *autosave_regs)
+{
+	printf("Memory management fault\n");
+	dump_regs(autosave_regs);
+	bad_mode();
+}
+
+void do_bus_fault(struct autosave_regs *autosave_regs)
+{
+	printf("Bus fault\n");
+	dump_regs(autosave_regs);
+	bad_mode();
+}
+
+void do_usage_fault(struct autosave_regs *autosave_regs)
+{
+	printf("Usage fault\n");
+	dump_regs(autosave_regs);
+	bad_mode();
+}
+
+void do_invalid_entry(struct autosave_regs *autosave_regs)
+{
+	printf("Exception\n");
+	dump_regs(autosave_regs);
+	bad_mode();
+}
diff --git a/arch/arm/lib/relocate.S b/arch/arm/lib/relocate.S
index 92f531452d..475d503dd9 100644
--- a/arch/arm/lib/relocate.S
+++ b/arch/arm/lib/relocate.S
@@ -9,6 +9,9 @@
 #include <asm-offsets.h>
 #include <config.h>
 #include <linux/linkage.h>
+#ifdef CONFIG_CPU_V7M
+#include <asm/armv7m.h>
+#endif
 
 /*
  * Default/weak exception vectors relocation routine
@@ -23,6 +26,15 @@
 
 ENTRY(relocate_vectors)
 
+#ifdef CONFIG_CPU_V7M
+	/*
+	 * On ARMv7-M we only have to write the new vector address
+	 * to VTOR register.
+	 */
+	ldr	r0, [r9, #GD_RELOCADDR]	/* r0 = gd->relocaddr */
+	ldr	r1, =V7M_SCB_BASE
+	str	r0, [r1, V7M_SCB_VTOR]
+#else
 #ifdef CONFIG_HAS_VBAR
 	/*
 	 * If the ARM processor has the security extensions,
@@ -47,6 +59,7 @@ ENTRY(relocate_vectors)
 	ldmia	r0!, {r2-r8,r10}
 	stmia	r1!, {r2-r8,r10}
 #endif
+#endif
 	bx	lr
 
 ENDPROC(relocate_vectors)
diff --git a/arch/arm/lib/vectors_m.S b/arch/arm/lib/vectors_m.S
new file mode 100644
index 0000000000..abc7f88e00
--- /dev/null
+++ b/arch/arm/lib/vectors_m.S
@@ -0,0 +1,57 @@
+/*
+ * (C) Copyright 2015
+ * Kamil Lulko, <rev13@wp.pl>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <config.h>
+#include <asm/armv7m.h>
+#include <linux/linkage.h>
+
+.type __hard_fault_entry, %function
+__hard_fault_entry:
+	mov	r0, sp	@ pass auto-saved registers as argument
+	b	do_hard_fault
+
+.type __mm_fault_entry, %function
+__mm_fault_entry:
+	mov	r0, sp	@ pass auto-saved registers as argument
+	b	do_mm_fault
+
+.type __bus_fault_entry, %function
+__bus_fault_entry:
+	mov	r0, sp	@ pass auto-saved registers as argument
+	b	do_bus_fault
+
+.type __usage_fault_entry, %function
+__usage_fault_entry:
+	mov	r0, sp	@ pass auto-saved registers as argument
+	b	do_usage_fault
+
+.type __invalid_entry, %function
+__invalid_entry:
+	mov	r0, sp	@ pass auto-saved registers as argument
+	b	do_invalid_entry
+
+   .section  .vectors
+ENTRY(_start)
+	.long	CONFIG_SYS_INIT_SP_ADDR		@ 0 - Reset stack pointer
+	.long	reset				@ 1 - Reset
+	.long	__invalid_entry			@ 2 - NMI
+	.long	__hard_fault_entry		@ 3 - HardFault
+	.long	__mm_fault_entry		@ 4 - MemManage
+	.long	__bus_fault_entry		@ 5 - BusFault
+	.long	__usage_fault_entry		@ 6 - UsageFault
+	.long	__invalid_entry			@ 7 - Reserved
+	.long	__invalid_entry			@ 8 - Reserved
+	.long	__invalid_entry			@ 9 - Reserved
+	.long	__invalid_entry			@ 10 - Reserved
+	.long	__invalid_entry			@ 11 - SVCall
+	.long	__invalid_entry			@ 12 - Debug Monitor
+	.long	__invalid_entry			@ 13 - Reserved
+	.long	__invalid_entry			@ 14 - PendSV
+	.long	__invalid_entry			@ 15 - SysTick
+	.rept	255 - 16
+	.long	__invalid_entry			@ 16..255 - External Interrupts
+	.endr