ARM: Add ARMv7-M support

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

arch/arm/Kconfig

@@ -33,6 +33,9 @@ config CPU_V7
         bool
         select HAS_VBAR
 
+config CPU_V7M
+	bool
+
 config CPU_PXA
         bool
 
@@ -47,6 +50,7 @@ config SYS_CPU
         default "arm1136" if CPU_ARM1136
         default "arm1176" if CPU_ARM1176
         default "armv7" if CPU_V7
+        default "armv7m" if CPU_V7M
         default "pxa" if CPU_PXA
         default "sa1100" if CPU_SA1100
 	default "armv8" if ARM64

arch/arm/cpu/armv7m/Makefile

@@ -0,0 +1,9 @@
+#
+# (C) Copyright 2000-2006
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+extra-y := start.o
+obj-y += cpu.o

arch/arm/cpu/armv7m/config.mk

@@ -0,0 +1,8 @@
+#
+# (C) Copyright 2015
+# Kamil Lulko, <rev13@wp.pl>
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+PLATFORM_CPPFLAGS += -march=armv7-m -mthumb

arch/arm/cpu/armv7m/cpu.c

@@ -0,0 +1,35 @@
+/*
+ * (C) Copyright 2010,2011
+ * Vladimir Khusainov, Emcraft Systems, vlad@emcraft.com
+ *
+ * (C) Copyright 2015
+ * Kamil Lulko, <rev13@wp.pl>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <asm/io.h>
+#include <asm/armv7m.h>
+
+/*
+ * This is called right before passing control to
+ * the Linux kernel point.
+ */
+int cleanup_before_linux(void)
+{
+	return 0;
+}
+
+/*
+ * Perform the low-level reset.
+ */
+void reset_cpu(ulong addr)
+{
+	/*
+	 * Perform reset but keep priority group unchanged.
+	 */
+	writel((V7M_AIRCR_VECTKEY << V7M_AIRCR_VECTKEY_SHIFT)
+		| (V7M_SCB->aircr & V7M_AIRCR_PRIGROUP_MSK)
+		| V7M_AIRCR_SYSRESET, &V7M_SCB->aircr);
+}

arch/arm/cpu/armv7m/start.S

@@ -0,0 +1,15 @@
+/*
+ * (C) Copyright 2015
+ * Kamil Lulko, <rev13@wp.pl>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+.globl	reset
+.type reset, %function
+reset:
+	b	_main
+
+.globl	c_runtime_cpu_setup
+c_runtime_cpu_setup:
+	mov	pc, lr

arch/arm/include/asm/armv7m.h

@@ -0,0 +1,60 @@
+/*
+ * (C) Copyright 2010,2011
+ * Vladimir Khusainov, Emcraft Systems, vlad@emcraft.com
+ *
+ * (C) Copyright 2015
+ * Kamil Lulko, <rev13@wp.pl>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef ARMV7M_H
+#define ARMV7M_H
+
+#if defined(__ASSEMBLY__)
+.syntax unified
+.thumb
+#endif
+
+#define V7M_SCB_BASE		0xE000ED00
+#define V7M_MPU_BASE		0xE000ED90
+
+#define V7M_SCB_VTOR		0x08
+
+#if !defined(__ASSEMBLY__)
+struct v7m_scb {
+	uint32_t cpuid;		/* CPUID Base Register */
+	uint32_t icsr;		/* Interrupt Control and State Register */
+	uint32_t vtor;		/* Vector Table Offset Register */
+	uint32_t aircr;		/* App Interrupt and Reset Control Register */
+};
+#define V7M_SCB				((struct v7m_scb *)V7M_SCB_BASE)
+
+#define V7M_AIRCR_VECTKEY		0x5fa
+#define V7M_AIRCR_VECTKEY_SHIFT		16
+#define V7M_AIRCR_ENDIAN		(1 << 15)
+#define V7M_AIRCR_PRIGROUP_SHIFT	8
+#define V7M_AIRCR_PRIGROUP_MSK		(0x7 << V7M_AIRCR_PRIGROUP_SHIFT)
+#define V7M_AIRCR_SYSRESET		(1 << 2)
+
+#define V7M_ICSR_VECTACT_MSK		0xFF
+
+struct v7m_mpu {
+	uint32_t type;		/* Type Register */
+	uint32_t ctrl;		/* Control Register */
+	uint32_t rnr;		/* Region Number Register */
+	uint32_t rbar;		/* Region Base Address Register */
+	uint32_t rasr;		/* Region Attribute and Size Register */
+};
+#define V7M_MPU				((struct v7m_mpu *)V7M_MPU_BASE)
+
+#define V7M_MPU_CTRL_ENABLE		(1 << 0)
+#define V7M_MPU_CTRL_HFNMIENA		(1 << 1)
+
+#define V7M_MPU_RASR_EN			(1 << 0)
+#define V7M_MPU_RASR_SIZE_BITS		1
+#define V7M_MPU_RASR_SIZE_4GB		(31 << V7M_MPU_RASR_SIZE_BITS)
+#define V7M_MPU_RASR_AP_RW_RW		(3 << 24)
+
+#endif /* !defined(__ASSEMBLY__) */
+#endif /* ARMV7M_H */

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

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

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();
+}

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)

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