ARM: 7861/1: cacheflush: consolidate single-CPU ARMv7 cache disabling code

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@linaro.org>
Acked-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 52 insertions, 98 deletions

diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index 15f2d5bf8875..ee753f1749cd 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -435,4 +435,50 @@ 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.  ip is saved as well if ever r12-clobbering
+ *   trampoline are inserted by the linker and to keep sp 64-bit aligned.
+ */
+#define v7_exit_coherency_flush(level) \
+        asm volatile( \
+        "stmfd  sp!, {fp, ip} \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" \
+        "ldmfd  sp!, {fp, ip}" \
+        : : : "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 3a6384c6c435..14d499688736 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 e6eb48192912..4eb92ebfd953 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);