diff options
Diffstat (limited to 'arch/arm/mach-mvebu/coherency_ll.S')
| -rw-r--r-- | arch/arm/mach-mvebu/coherency_ll.S | 77 |
1 files changed, 49 insertions, 28 deletions
diff --git a/arch/arm/mach-mvebu/coherency_ll.S b/arch/arm/mach-mvebu/coherency_ll.S index 6828f9f157b0..510c29e079ca 100644 --- a/arch/arm/mach-mvebu/coherency_ll.S +++ b/arch/arm/mach-mvebu/coherency_ll.S @@ -24,52 +24,69 @@ #include <asm/cp15.h> .text -/* Returns with the coherency address in r1 (r0 is untouched)*/ +/* Returns the coherency base address in r1 (r0 is untouched) */ ENTRY(ll_get_coherency_base) mrc p15, 0, r1, c1, c0, 0 tst r1, #CR_M @ Check MMU bit enabled bne 1f - /* use physical address of the coherency register */ + /* + * MMU is disabled, use the physical address of the coherency + * base address. + */ adr r1, 3f ldr r3, [r1] ldr r1, [r1, r3] b 2f 1: - /* use virtual address of the coherency register */ + /* + * MMU is enabled, use the virtual address of the coherency + * base address. + */ ldr r1, =coherency_base ldr r1, [r1] 2: mov pc, lr ENDPROC(ll_get_coherency_base) -/* Returns with the CPU ID in r3 (r0 is untouched)*/ -ENTRY(ll_get_cpuid) +/* + * 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 15, 0, r3, cr0, cr0, 5 and r3, r3, #15 mov r2, #(1 << 24) lsl r3, r2, r3 -ARM_BE8(rev r1, r1) +ARM_BE8(rev r3, r3) mov pc, lr -ENDPROC(ll_get_cpuid) +ENDPROC(ll_get_coherency_cpumask) -/* ll_add_cpu_to_smp_group, ll_enable_coherency and - * ll_disable_coherency use strex/ldrex whereas MMU can be off. The - * Armada XP SoC has an exclusive monitor that can track transactions - * to Device and/or SO and as such also when MMU is disabled the - * exclusive transactions will be functional +/* + * 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) /* - * r0 being untouched in ll_get_coherency_base and - * ll_get_cpuid, we can use it to save lr modifing it with the - * following bl + * 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. */ - mov r0, lr + mov r0, lr bl ll_get_coherency_base - bl ll_get_cpuid - mov lr, r0 + bl ll_get_coherency_cpumask + mov lr, r0 add r0, r1, #ARMADA_XP_CFB_CFG_REG_OFFSET 1: ldrex r2, [r0] @@ -82,13 +99,15 @@ ENDPROC(ll_add_cpu_to_smp_group) ENTRY(ll_enable_coherency) /* - * r0 being untouched in ll_get_coherency_base and - * ll_get_cpuid, we can use it to save lr modifing it with the - * following bl + * 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. */ mov r0, lr bl ll_get_coherency_base - bl ll_get_cpuid + bl ll_get_coherency_cpumask mov lr, r0 add r0, r1, #ARMADA_XP_CFB_CTL_REG_OFFSET 1: @@ -104,14 +123,16 @@ ENDPROC(ll_enable_coherency) ENTRY(ll_disable_coherency) /* - * r0 being untouched in ll_get_coherency_base and - * ll_get_cpuid, we can use it to save lr modifing it with the - * following bl + * 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. */ - mov r0, lr + mov r0, lr bl ll_get_coherency_base - bl ll_get_cpuid - mov lr, r0 + bl ll_get_coherency_cpumask + mov lr, r0 add r0, r1, #ARMADA_XP_CFB_CTL_REG_OFFSET 1: ldrex r2, [r0] |