ARM: 6385/1: setup: detect aliasing I-cache when D-cache is non-aliasing

Currently, the Kernel assumes that if a CPU has a non-aliasing D-cache
then the I-cache is also non-aliasing. This may not be true on ARM cores
from v6 onwards, which may have aliasing I-caches but non-aliasing
D-caches.

This patch adds a cpu_has_aliasing_icache function, which is called from
cacheid_init and adds CACHEID_VIPT_I_ALIASING to the cacheid when
appropriate. A utility macro, icache_is_vipt_aliasing(), is also
provided.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 42 insertions, 5 deletions

diff --git a/arch/arm/include/asm/cachetype.h b/arch/arm/include/asm/cachetype.h
index d3a4c2cb9f2f..c023db09fcc1 100644
--- a/arch/arm/include/asm/cachetype.h
+++ b/arch/arm/include/asm/cachetype.h
@@ -6,6 +6,7 @@
 #define CACHEID_VIPT_ALIASING           (1 << 2)
 #define CACHEID_VIPT                    (CACHEID_VIPT_ALIASING|CACHEID_VIPT_NONALIASING)
 #define CACHEID_ASID_TAGGED             (1 << 3)
+#define CACHEID_VIPT_I_ALIASING         (1 << 4)
 
 extern unsigned int cacheid;
 
@@ -14,15 +15,18 @@ extern unsigned int cacheid;
 #define cache_is_vipt_nonaliasing()     cacheid_is(CACHEID_VIPT_NONALIASING)
 #define cache_is_vipt_aliasing()        cacheid_is(CACHEID_VIPT_ALIASING)
 #define icache_is_vivt_asid_tagged()    cacheid_is(CACHEID_ASID_TAGGED)
+#define icache_is_vipt_aliasing()       cacheid_is(CACHEID_VIPT_I_ALIASING)
 
 /*
  * __LINUX_ARM_ARCH__ is the minimum supported CPU architecture
  * Mask out support which will never be present on newer CPUs.
  * - v6+ is never VIVT
- * - v7+ VIPT never aliases
+ * - v7+ VIPT never aliases on D-side
  */
 #if __LINUX_ARM_ARCH__ >= 7
-#define __CACHEID_ARCH_MIN      (CACHEID_VIPT_NONALIASING | CACHEID_ASID_TAGGED)
+#define __CACHEID_ARCH_MIN      (CACHEID_VIPT_NONALIASING |\
+                                 CACHEID_ASID_TAGGED |\
+                                 CACHEID_VIPT_I_ALIASING)
 #elif __LINUX_ARM_ARCH__ >= 6
 #define __CACHEID_ARCH_MIN      (~CACHEID_VIVT)
 #else
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index d5231ae7355a..9fc483393bae 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -238,6 +238,34 @@ int cpu_architecture(void)
         return cpu_arch;
 }
 
+static int cpu_has_aliasing_icache(unsigned int arch)
+{
+        int aliasing_icache;
+        unsigned int id_reg, num_sets, line_size;
+
+        /* arch specifies the register format */
+        switch (arch) {
+        case CPU_ARCH_ARMv7:
+                asm("mcr        p15, 2, %1, c0, c0, 0   @ set CSSELR\n"
+                    "isb\n"
+                    "mrc        p15, 1, %0, c0, c0, 0   @ read CCSIDR"
+                    : "=r" (id_reg)
+                    : "r" (1));
+                line_size = 4 << ((id_reg & 0x7) + 2);
+                num_sets = ((id_reg >> 13) & 0x7fff) + 1;
+                aliasing_icache = (line_size * num_sets) > PAGE_SIZE;
+                break;
+        case CPU_ARCH_ARMv6:
+                aliasing_icache = read_cpuid_cachetype() & (1 << 11);
+                break;
+        default:
+                /* I-cache aliases will be handled by D-cache aliasing code */
+                aliasing_icache = 0;
+        }
+
+        return aliasing_icache;
+}
+
 static void __init cacheid_init(void)
 {
         unsigned int cachetype = read_cpuid_cachetype();
@@ -249,10 +277,15 @@ static void __init cacheid_init(void)
                         cacheid = CACHEID_VIPT_NONALIASING;
                         if ((cachetype & (3 << 14)) == 1 << 14)
                                 cacheid |= CACHEID_ASID_TAGGED;
-                } else if (cachetype & (1 << 23))
+                        else if (cpu_has_aliasing_icache(CPU_ARCH_ARMv7))
+                                cacheid |= CACHEID_VIPT_I_ALIASING;
+                } else if (cachetype & (1 << 23)) {
                         cacheid = CACHEID_VIPT_ALIASING;
-                else
+                } else {
                         cacheid = CACHEID_VIPT_NONALIASING;
+                        if (cpu_has_aliasing_icache(CPU_ARCH_ARMv6))
+                                cacheid |= CACHEID_VIPT_I_ALIASING;
+                }
         } else {
                 cacheid = CACHEID_VIVT;
         }
@@ -263,7 +296,7 @@ static void __init cacheid_init(void)
                 cache_is_vipt_nonaliasing() ? "VIPT nonaliasing" : "unknown",
                 cache_is_vivt() ? "VIVT" :
                 icache_is_vivt_asid_tagged() ? "VIVT ASID tagged" :
-                cache_is_vipt_aliasing() ? "VIPT aliasing" :
+                icache_is_vipt_aliasing() ? "VIPT aliasing" :
                 cache_is_vipt_nonaliasing() ? "VIPT nonaliasing" : "unknown");
 }