arch/arm/mach-mvebu/coherency_ll.S

Source file repositories/reference/linux-study-clean/arch/arm/mach-mvebu/coherency_ll.S

File Facts

System
Linux kernel
Corpus path
arch/arm/mach-mvebu/coherency_ll.S
Extension
.S
Size
4134 bytes
Lines
160
Domain
Architecture Layer
Bucket
arch/arm
Inferred role
Architecture Layer: arch/arm
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <linux/linkage.h>
#define ARMADA_XP_CFB_CTL_REG_OFFSET 0x0
#define ARMADA_XP_CFB_CFG_REG_OFFSET 0x4

#include <asm/assembler.h>
#include <asm/cp15.h>

	.arch armv7-a
	.text
/*
 * Returns the coherency base address in r1 (r0 is untouched), or 0 if
 * the coherency fabric is not enabled.
 */
ENTRY(ll_get_coherency_base)
	mrc	p15, 0, r1, c1, c0, 0
	tst	r1, #CR_M @ Check MMU bit enabled
	bne	1f

	/*
	 * MMU is disabled, use the physical address of the coherency
	 * base address, (or 0x0 if the coherency fabric is not mapped)
	 */
	adr	r1, 3f
	ldr	r3, [r1]
	ldr	r1, [r1, r3]
	b	2f
1:
	/*
	 * MMU is enabled, use the virtual address of the coherency
	 * base address.
	 */
	ldr	r1, =coherency_base
	ldr	r1, [r1]
2:
	ret	lr
ENDPROC(ll_get_coherency_base)

/*
 * Returns the coherency CPU mask in r3 (r0 is untouched). This
 * coherency CPU mask can be used with the coherency fabric
 * configuration and control registers. Note that the mask is already
 * endian-swapped as appropriate so that the calling functions do not
 * have to care about endianness issues while accessing the coherency
 * fabric registers
 */
ENTRY(ll_get_coherency_cpumask)
	mrc	p15, 0, r3, cr0, cr0, 5
	and	r3, r3, #15
	mov	r2, #(1 << 24)
	lsl	r3, r2, r3
ARM_BE8(rev	r3, r3)
	ret	lr
ENDPROC(ll_get_coherency_cpumask)

/*
 * ll_add_cpu_to_smp_group(), ll_enable_coherency() and
 * ll_disable_coherency() use the strex/ldrex instructions while the
 * MMU can be disabled. The Armada XP SoC has an exclusive monitor
 * that tracks transactions to Device and/or SO memory and thanks to
 * that, exclusive transactions are functional even when the MMU is
 * disabled.
 */

ENTRY(ll_add_cpu_to_smp_group)
	/*
	 * As r0 is not modified by ll_get_coherency_base() and
	 * ll_get_coherency_cpumask(), we use it to temporarly save lr
	 * and avoid it being modified by the branch and link
	 * calls. This function is used very early in the secondary
	 * CPU boot, and no stack is available at this point.

Annotation

Implementation Notes