powerpc/4xx: Extended DCR support v2

This adds supports to the "extended" DCR addressing via the indirect
mfdcrx/mtdcrx instructions supported by some 4xx cores (440H6 and
later).

I enabled the feature for now only on AMCC 460 chips.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

4 files changed, 65 insertions, 17 deletions

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index f3d9d7417166..31888322d76a 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -164,6 +164,7 @@ extern const char *powerpc_base_platform;
 #define CPU_FTR_NEED_PAIRED_STWCX       ASM_CONST(0x0000000004000000)
 #define CPU_FTR_LWSYNC                  ASM_CONST(0x0000000008000000)
 #define CPU_FTR_NOEXECUTE               ASM_CONST(0x0000000010000000)
+#define CPU_FTR_INDEXED_DCR             ASM_CONST(0x0000000020000000)
 
 /*
  * Add the 64-bit processor unique features in the top half of the word;
@@ -369,6 +370,8 @@ extern const char *powerpc_base_platform;
 #define CPU_FTRS_8XX    (CPU_FTR_USE_TB)
 #define CPU_FTRS_40X    (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | CPU_FTR_NOEXECUTE)
 #define CPU_FTRS_44X    (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | CPU_FTR_NOEXECUTE)
+#define CPU_FTRS_440x6  (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | CPU_FTR_NOEXECUTE | \
+            CPU_FTR_INDEXED_DCR)
 #define CPU_FTRS_E200   (CPU_FTR_USE_TB | CPU_FTR_SPE_COMP | \
             CPU_FTR_NODSISRALIGN | CPU_FTR_COHERENT_ICACHE | \
             CPU_FTR_UNIFIED_ID_CACHE | CPU_FTR_NOEXECUTE)
@@ -455,7 +458,7 @@ enum {
             CPU_FTRS_40X |
 #endif
 #ifdef CONFIG_44x
-            CPU_FTRS_44X |
+            CPU_FTRS_44X | CPU_FTRS_440x6 |
 #endif
 #ifdef CONFIG_E200
             CPU_FTRS_E200 |
@@ -495,7 +498,7 @@ enum {
             CPU_FTRS_40X &
 #endif
 #ifdef CONFIG_44x
-            CPU_FTRS_44X &
+            CPU_FTRS_44X & CPU_FTRS_440x6 &
 #endif
 #ifdef CONFIG_E200
             CPU_FTRS_E200 &
diff --git a/arch/powerpc/include/asm/dcr-native.h b/arch/powerpc/include/asm/dcr-native.h
index 72d2b72c7390..7d2e6235726d 100644
--- a/arch/powerpc/include/asm/dcr-native.h
+++ b/arch/powerpc/include/asm/dcr-native.h
@@ -23,6 +23,7 @@
 #ifndef __ASSEMBLY__
 
 #include <linux/spinlock.h>
+#include <asm/cputable.h>
 
 typedef struct {
         unsigned int base;
@@ -39,23 +40,45 @@ static inline bool dcr_map_ok_native(dcr_host_native_t host)
 #define dcr_read_native(host, dcr_n)            mfdcr(dcr_n + host.base)
 #define dcr_write_native(host, dcr_n, value)    mtdcr(dcr_n + host.base, value)
 
-/* Device Control Registers */
-void __mtdcr(int reg, unsigned int val);
-unsigned int __mfdcr(int reg);
+/* Table based DCR accessors */
+extern void __mtdcr(unsigned int reg, unsigned int val);
+extern unsigned int __mfdcr(unsigned int reg);
+
+/* mfdcrx/mtdcrx instruction based accessors. We hand code
+ * the opcodes in order not to depend on newer binutils
+ */
+static inline unsigned int mfdcrx(unsigned int reg)
+{
+        unsigned int ret;
+        asm volatile(".long 0x7c000206 | (%0 << 21) | (%1 << 16)"
+                     : "=r" (ret) : "r" (reg));
+        return ret;
+}
+
+static inline void mtdcrx(unsigned int reg, unsigned int val)
+{
+        asm volatile(".long 0x7c000306 | (%0 << 21) | (%1 << 16)"
+                     : : "r" (val), "r" (reg));
+}
+
 #define mfdcr(rn)                                               \
         ({unsigned int rval;                                    \
-        if (__builtin_constant_p(rn))                           \
+        if (__builtin_constant_p(rn) && rn < 1024)              \
                 asm volatile("mfdcr %0," __stringify(rn)        \
                               : "=r" (rval));                   \
+        else if (likely(cpu_has_feature(CPU_FTR_INDEXED_DCR)))  \
+                rval = mfdcrx(rn);                              \
         else                                                    \
                 rval = __mfdcr(rn);                             \
         rval;})
 
 #define mtdcr(rn, v)                                            \
 do {                                                            \
-        if (__builtin_constant_p(rn))                           \
+        if (__builtin_constant_p(rn) && rn < 1024)              \
                 asm volatile("mtdcr " __stringify(rn) ",%0"     \
                               : : "r" (v));                     \
+        else if (likely(cpu_has_feature(CPU_FTR_INDEXED_DCR)))  \
+                mtdcrx(rn, v);                                  \
         else                                                    \
                 __mtdcr(rn, v);                                 \
 } while (0)
@@ -69,8 +92,13 @@ static inline unsigned __mfdcri(int base_addr, int base_data, int reg)
         unsigned int val;
 
         spin_lock_irqsave(&dcr_ind_lock, flags);
-        __mtdcr(base_addr, reg);
-        val = __mfdcr(base_data);
+        if (cpu_has_feature(CPU_FTR_INDEXED_DCR)) {
+                mtdcrx(base_addr, reg);
+                val = mfdcrx(base_data);
+        } else {
+                __mtdcr(base_addr, reg);
+                val = __mfdcr(base_data);
+        }
         spin_unlock_irqrestore(&dcr_ind_lock, flags);
         return val;
 }
@@ -81,8 +109,13 @@ static inline void __mtdcri(int base_addr, int base_data, int reg,
         unsigned long flags;
 
         spin_lock_irqsave(&dcr_ind_lock, flags);
-        __mtdcr(base_addr, reg);
-        __mtdcr(base_data, val);
+        if (cpu_has_feature(CPU_FTR_INDEXED_DCR)) {
+                mtdcrx(base_addr, reg);
+                mtdcrx(base_data, val);
+        } else {
+                __mtdcr(base_addr, reg);
+                __mtdcr(base_data, val);
+        }
         spin_unlock_irqrestore(&dcr_ind_lock, flags);
 }
 
@@ -93,9 +126,15 @@ static inline void __dcri_clrset(int base_addr, int base_data, int reg,
         unsigned int val;
 
         spin_lock_irqsave(&dcr_ind_lock, flags);
-        __mtdcr(base_addr, reg);
-        val = (__mfdcr(base_data) & ~clr) | set;
-        __mtdcr(base_data, val);
+        if (cpu_has_feature(CPU_FTR_INDEXED_DCR)) {
+                mtdcrx(base_addr, reg);
+                val = (mfdcrx(base_data) & ~clr) | set;
+                mtdcrx(base_data, val);
+        } else {
+                __mtdcr(base_addr, reg);
+                val = (__mfdcr(base_data) & ~clr) | set;
+                __mtdcr(base_data, val);
+        }
         spin_unlock_irqrestore(&dcr_ind_lock, flags);
 }
 
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index 7e8719504f39..921a2298d8e3 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -1509,7 +1509,7 @@ static struct cpu_spec __initdata cpu_specs[] = {
                 .pvr_mask               = 0xffff0002,
                 .pvr_value              = 0x13020002,
                 .cpu_name               = "460EX",
-                .cpu_features           = CPU_FTRS_44X,
+                .cpu_features           = CPU_FTRS_440x6,
                 .cpu_user_features      = COMMON_USER_BOOKE | PPC_FEATURE_HAS_FPU,
                 .icache_bsize           = 32,
                 .dcache_bsize           = 32,
@@ -1521,7 +1521,7 @@ static struct cpu_spec __initdata cpu_specs[] = {
                 .pvr_mask               = 0xffff0002,
                 .pvr_value              = 0x13020000,
                 .cpu_name               = "460GT",
-                .cpu_features           = CPU_FTRS_44X,
+                .cpu_features           = CPU_FTRS_440x6,
                 .cpu_user_features      = COMMON_USER_BOOKE | PPC_FEATURE_HAS_FPU,
                 .icache_bsize           = 32,
                 .dcache_bsize           = 32,
diff --git a/arch/powerpc/sysdev/dcr-low.S b/arch/powerpc/sysdev/dcr-low.S
index 2078f39e2f17..d3098ef1404a 100644
--- a/arch/powerpc/sysdev/dcr-low.S
+++ b/arch/powerpc/sysdev/dcr-low.S
@@ -11,14 +11,20 @@
 
 #include <asm/ppc_asm.h>
 #include <asm/processor.h>
+#include <asm/bug.h>
 
 #define DCR_ACCESS_PROLOG(table) \
+        cmpli   cr0,r3,1024;     \
         rlwinm  r3,r3,4,18,27;   \
         lis     r5,table@h;      \
         ori     r5,r5,table@l;   \
         add     r3,r3,r5;        \
+        bge-    1f;              \
         mtctr   r3;              \
-        bctr
+        bctr;                    \
+1:      trap;                    \
+        EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,0;  \
+        blr
 
 _GLOBAL(__mfdcr)
         DCR_ACCESS_PROLOG(__mfdcr_table)