[PATCH] ARM: cacheflush: consolidate single-CPU ARMv7 cache disabling code
Nicolas Pitre
nicolas.pitre at linaro.org
Tue Oct 15 23:34:46 EDT 2013
This code is becoming duplicated in many places. So let's consolidate
it into a handy macro that is known to be right and available for reuse.
Signed-off-by: Nicolas Pitre <nico at linaro.org>
---
I forgot which version this one is. As far as I know, I've incorporated
most review comments, and ignored conflicting ones which tended to look
like bikeshedding and attempted to compensate for them with additional
code comments.
ACK?
arch/arm/include/asm/cacheflush.h | 45 +++++++++++++++++++++++++++++++
arch/arm/mach-vexpress/dcscb.c | 56 +++------------------------------------
arch/arm/mach-vexpress/tc2_pm.c | 48 ++-------------------------------
3 files changed, 51 insertions(+), 98 deletions(-)
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index 15f2d5bf88..60a0a79b1a 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -435,4 +435,49 @@ static inline void __sync_cache_range_r(volatile void *p, size_t size)
#define sync_cache_w(ptr) __sync_cache_range_w(ptr, sizeof *(ptr))
#define sync_cache_r(ptr) __sync_cache_range_r(ptr, sizeof *(ptr))
+/*
+ * Disabling cache access for one CPU in an ARMv7 SMP system is tricky.
+ * To do so we must:
+ *
+ * - Clear the SCTLR.C bit to prevent further cache allocations
+ * - Flush the desired level of cache
+ * - Clear the ACTLR "SMP" bit to disable local coherency
+ *
+ * ... and so without any intervening memory access in between those steps,
+ * not even to the stack.
+ *
+ * WARNING -- After this has been called:
+ *
+ * - No ldrex/strex (and similar) instructions must be used.
+ * - The CPU is obviously no longer coherent with the other CPUs.
+ * - This is unlikely to work as expected if Linux is running non-secure.
+ *
+ * Note:
+ *
+ * - This is known to apply to several ARMv7 processor implementations,
+ * however some exceptions may exist. Caveat emptor.
+ *
+ * - The clobber list is dictated by the call to v7_flush_dcache_*.
+ * fp is preserved to the stack explicitly prior disabling the cache
+ * since adding it to the clobber list is incompatible with having
+ * CONFIG_FRAME_POINTER=y.
+ */
+#define v7_exit_coherency_flush(level) \
+ asm volatile( \
+ "str fp, [sp, #-4]! \n\t" \
+ "mrc p15, 0, r0, c1, c0, 0 @ get SCTLR \n\t" \
+ "bic r0, r0, #"__stringify(CR_C)" \n\t" \
+ "mcr p15, 0, r0, c1, c0, 0 @ set SCTLR \n\t" \
+ "isb \n\t" \
+ "bl v7_flush_dcache_"__stringify(level)" \n\t" \
+ "clrex \n\t" \
+ "mrc p15, 0, r0, c1, c0, 1 @ get ACTLR \n\t" \
+ "bic r0, r0, #(1 << 6) @ disable local coherency \n\t" \
+ "mcr p15, 0, r0, c1, c0, 1 @ set ACTLR \n\t" \
+ "isb \n\t" \
+ "dsb \n\t" \
+ "ldr fp, [sp], #4" \
+ : : : "r0","r1","r2","r3","r4","r5","r6","r7", \
+ "r9","r10","lr","memory" )
+
#endif
diff --git a/arch/arm/mach-vexpress/dcscb.c b/arch/arm/mach-vexpress/dcscb.c
index 3a6384c6c4..14d4996887 100644
--- a/arch/arm/mach-vexpress/dcscb.c
+++ b/arch/arm/mach-vexpress/dcscb.c
@@ -133,38 +133,8 @@ static void dcscb_power_down(void)
if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
arch_spin_unlock(&dcscb_lock);
- /*
- * Flush all cache levels for this cluster.
- *
- * To do so we do:
- * - Clear the SCTLR.C bit to prevent further cache allocations
- * - Flush the whole cache
- * - Clear the ACTLR "SMP" bit to disable local coherency
- *
- * Let's do it in the safest possible way i.e. with
- * no memory access within the following sequence
- * including to the stack.
- *
- * Note: fp is preserved to the stack explicitly prior doing
- * this since adding it to the clobber list is incompatible
- * with having CONFIG_FRAME_POINTER=y.
- */
- asm volatile(
- "str fp, [sp, #-4]! \n\t"
- "mrc p15, 0, r0, c1, c0, 0 @ get CR \n\t"
- "bic r0, r0, #"__stringify(CR_C)" \n\t"
- "mcr p15, 0, r0, c1, c0, 0 @ set CR \n\t"
- "isb \n\t"
- "bl v7_flush_dcache_all \n\t"
- "clrex \n\t"
- "mrc p15, 0, r0, c1, c0, 1 @ get AUXCR \n\t"
- "bic r0, r0, #(1 << 6) @ disable local coherency \n\t"
- "mcr p15, 0, r0, c1, c0, 1 @ set AUXCR \n\t"
- "isb \n\t"
- "dsb \n\t"
- "ldr fp, [sp], #4"
- : : : "r0","r1","r2","r3","r4","r5","r6","r7",
- "r9","r10","lr","memory");
+ /* Flush all cache levels for this cluster. */
+ v7_exit_coherency_flush(all);
/*
* This is a harmless no-op. On platforms with a real
@@ -183,26 +153,8 @@ static void dcscb_power_down(void)
} else {
arch_spin_unlock(&dcscb_lock);
- /*
- * Flush the local CPU cache.
- * Let's do it in the safest possible way as above.
- */
- asm volatile(
- "str fp, [sp, #-4]! \n\t"
- "mrc p15, 0, r0, c1, c0, 0 @ get CR \n\t"
- "bic r0, r0, #"__stringify(CR_C)" \n\t"
- "mcr p15, 0, r0, c1, c0, 0 @ set CR \n\t"
- "isb \n\t"
- "bl v7_flush_dcache_louis \n\t"
- "clrex \n\t"
- "mrc p15, 0, r0, c1, c0, 1 @ get AUXCR \n\t"
- "bic r0, r0, #(1 << 6) @ disable local coherency \n\t"
- "mcr p15, 0, r0, c1, c0, 1 @ set AUXCR \n\t"
- "isb \n\t"
- "dsb \n\t"
- "ldr fp, [sp], #4"
- : : : "r0","r1","r2","r3","r4","r5","r6","r7",
- "r9","r10","lr","memory");
+ /* Disable and flush the local CPU cache. */
+ v7_exit_coherency_flush(louis);
}
__mcpm_cpu_down(cpu, cluster);
diff --git a/arch/arm/mach-vexpress/tc2_pm.c b/arch/arm/mach-vexpress/tc2_pm.c
index e6eb481929..4eb92ebfd9 100644
--- a/arch/arm/mach-vexpress/tc2_pm.c
+++ b/arch/arm/mach-vexpress/tc2_pm.c
@@ -156,32 +156,7 @@ static void tc2_pm_down(u64 residency)
: : "r" (0x400) );
}
- /*
- * We need to disable and flush the whole (L1 and L2) cache.
- * Let's do it in the safest possible way i.e. with
- * no memory access within the following sequence
- * including the stack.
- *
- * Note: fp is preserved to the stack explicitly prior doing
- * this since adding it to the clobber list is incompatible
- * with having CONFIG_FRAME_POINTER=y.
- */
- asm volatile(
- "str fp, [sp, #-4]! \n\t"
- "mrc p15, 0, r0, c1, c0, 0 @ get CR \n\t"
- "bic r0, r0, #"__stringify(CR_C)" \n\t"
- "mcr p15, 0, r0, c1, c0, 0 @ set CR \n\t"
- "isb \n\t"
- "bl v7_flush_dcache_all \n\t"
- "clrex \n\t"
- "mrc p15, 0, r0, c1, c0, 1 @ get AUXCR \n\t"
- "bic r0, r0, #(1 << 6) @ disable local coherency \n\t"
- "mcr p15, 0, r0, c1, c0, 1 @ set AUXCR \n\t"
- "isb \n\t"
- "dsb \n\t"
- "ldr fp, [sp], #4"
- : : : "r0","r1","r2","r3","r4","r5","r6","r7",
- "r9","r10","lr","memory");
+ v7_exit_coherency_flush(all);
cci_disable_port_by_cpu(mpidr);
@@ -197,26 +172,7 @@ static void tc2_pm_down(u64 residency)
arch_spin_unlock(&tc2_pm_lock);
- /*
- * We need to disable and flush only the L1 cache.
- * Let's do it in the safest possible way as above.
- */
- asm volatile(
- "str fp, [sp, #-4]! \n\t"
- "mrc p15, 0, r0, c1, c0, 0 @ get CR \n\t"
- "bic r0, r0, #"__stringify(CR_C)" \n\t"
- "mcr p15, 0, r0, c1, c0, 0 @ set CR \n\t"
- "isb \n\t"
- "bl v7_flush_dcache_louis \n\t"
- "clrex \n\t"
- "mrc p15, 0, r0, c1, c0, 1 @ get AUXCR \n\t"
- "bic r0, r0, #(1 << 6) @ disable local coherency \n\t"
- "mcr p15, 0, r0, c1, c0, 1 @ set AUXCR \n\t"
- "isb \n\t"
- "dsb \n\t"
- "ldr fp, [sp], #4"
- : : : "r0","r1","r2","r3","r4","r5","r6","r7",
- "r9","r10","lr","memory");
+ v7_exit_coherency_flush(louis);
}
__mcpm_cpu_down(cpu, cluster);
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