Better interface to run uncached cache setup code.

Signed-off-by: Thiemo Seufer <ths@networkno.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

6 files changed, 94 insertions, 27 deletions

diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index 037303412909..cf12caf80774 100644
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -2,8 +2,8 @@
 # Makefile for MIPS-specific library files..
 #
 
-lib-y   += csum_partial_copy.o memcpy.o promlib.o \
-           strlen_user.o strncpy_user.o strnlen_user.o
+lib-y   += csum_partial_copy.o memcpy.o promlib.o strlen_user.o strncpy_user.o \
+           strnlen_user.o uncached.o
 
 obj-y   += iomap.o
 
diff --git a/arch/mips/lib/uncached.c b/arch/mips/lib/uncached.c
new file mode 100644
index 000000000000..98ce89f8068b
--- /dev/null
+++ b/arch/mips/lib/uncached.c
@@ -0,0 +1,76 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2005 Thiemo Seufer
+ * Copyright (C) 2005  MIPS Technologies, Inc.  All rights reserved.
+ *      Author: Maciej W. Rozycki <macro@mips.com>
+ */
+
+#include <linux/init.h>
+
+#include <asm/addrspace.h>
+#include <asm/bug.h>
+
+#ifndef CKSEG2
+#define CKSEG2 CKSSEG
+#endif
+#ifndef TO_PHYS_MASK
+#define TO_PHYS_MASK -1
+#endif
+
+/*
+ * FUNC is executed in one of the uncached segments, depending on its
+ * original address as follows:
+ *
+ * 1. If the original address is in CKSEG0 or CKSEG1, then the uncached
+ *    segment used is CKSEG1.
+ * 2. If the original address is in XKPHYS, then the uncached segment
+ *    used is XKPHYS(2).
+ * 3. Otherwise it's a bug.
+ *
+ * The same remapping is done with the stack pointer.  Stack handling
+ * works because we don't handle stack arguments or more complex return
+ * values, so we can avoid sharing the same stack area between a cached
+ * and the uncached mode.
+ */
+unsigned long __init run_uncached(void *func)
+{
+        register long sp __asm__("$sp");
+        register long ret __asm__("$2");
+        long lfunc = (long)func, ufunc;
+        long usp;
+
+        if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
+                usp = CKSEG1ADDR(sp);
+        else if ((long long)sp >= (long long)PHYS_TO_XKPHYS(0LL, 0) &&
+                 (long long)sp < (long long)PHYS_TO_XKPHYS(8LL, 0))
+                usp = PHYS_TO_XKPHYS((long long)K_CALG_UNCACHED,
+                                     XKPHYS_TO_PHYS((long long)sp));
+        else {
+                BUG();
+                usp = sp;
+        }
+        if (lfunc >= (long)CKSEG0 && lfunc < (long)CKSEG2)
+                ufunc = CKSEG1ADDR(lfunc);
+        else if ((long long)lfunc >= (long long)PHYS_TO_XKPHYS(0LL, 0) &&
+                 (long long)lfunc < (long long)PHYS_TO_XKPHYS(8LL, 0))
+                ufunc = PHYS_TO_XKPHYS((long long)K_CALG_UNCACHED,
+                                       XKPHYS_TO_PHYS((long long)lfunc));
+        else {
+                BUG();
+                ufunc = lfunc;
+        }
+
+        __asm__ __volatile__ (
+                "       move    $16, $sp\n"
+                "       move    $sp, %1\n"
+                "       jalr    %2\n"
+                "       move    $sp, $16"
+                : "=r" (ret)
+                : "r" (usp), "r" (ufunc)
+                : "$16", "$31");
+
+        return ret;
+}
diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 48d731c2f08a..b90147399ea4 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -26,6 +26,7 @@
 #include <asm/system.h>
 #include <asm/mmu_context.h>
 #include <asm/war.h>
+#include <asm/cacheflush.h> /* for run_uncached() */
 
 static unsigned long icache_size, dcache_size, scache_size;
 
@@ -1119,7 +1120,6 @@ static int __init probe_scache(void)
         return 1;
 }
 
-typedef int (*probe_func_t)(unsigned long);
 extern int r5k_sc_init(void);
 extern int rm7k_sc_init(void);
 
@@ -1127,7 +1127,6 @@ static void __init setup_scache(void)
 {
         struct cpuinfo_mips *c = &current_cpu_data;
         unsigned int config = read_c0_config();
-        probe_func_t probe_scache_kseg1;
         int sc_present = 0;
 
         /*
@@ -1140,8 +1139,7 @@ static void __init setup_scache(void)
         case CPU_R4000MC:
         case CPU_R4400SC:
         case CPU_R4400MC:
-                probe_scache_kseg1 = (probe_func_t) (CKSEG1ADDR(&probe_scache));
-                sc_present = probe_scache_kseg1(config);
+                sc_present = run_uncached(probe_scache);
                 if (sc_present)
                         c->options |= MIPS_CPU_CACHE_CDEX_S;
                 break;
diff --git a/arch/mips/mm/sc-rm7k.c b/arch/mips/mm/sc-rm7k.c
index 4e92f931aaba..1df5aab82c13 100644
--- a/arch/mips/mm/sc-rm7k.c
+++ b/arch/mips/mm/sc-rm7k.c
@@ -15,6 +15,7 @@
 #include <asm/cacheops.h>
 #include <asm/mipsregs.h>
 #include <asm/processor.h>
+#include <asm/cacheflush.h> /* for run_uncached() */
 
 /* Primary cache parameters. */
 #define sc_lsize        32
@@ -96,25 +97,13 @@ static void rm7k_sc_inv(unsigned long addr, unsigned long size)
 }
 
 /*
- * This function is executed in the uncached segment CKSEG1.
- * It must not touch the stack, because the stack pointer still points
- * into CKSEG0.
- *
- * Three options:
- *      - Write it in assembly and guarantee that we don't use the stack.
- *      - Disable caching for CKSEG0 before calling it.
- *      - Pray that GCC doesn't randomly start using the stack.
- *
- * This being Linux, we obviously take the least sane of those options -
- * following DaveM's lead in c-r4k.c
- *
- * It seems we get our kicks from relying on unguaranteed behaviour in GCC
+ * This function is executed in uncached address space.
  */
 static __init void __rm7k_sc_enable(void)
 {
         int i;
 
-        set_c0_config(1 << 3);                          /* CONF_SE */
+        set_c0_config(R7K_CONF_SE);
 
         write_c0_taglo(0);
         write_c0_taghi(0);
@@ -127,24 +116,22 @@ static __init void __rm7k_sc_enable(void)
                       ".set mips0\n\t"
                       ".set reorder"
                       :
-                      : "r" (KSEG0ADDR(i)), "i" (Index_Store_Tag_SD));
+                      : "r" (CKSEG0ADDR(i)), "i" (Index_Store_Tag_SD));
         }
 }
 
 static __init void rm7k_sc_enable(void)
 {
-        void (*func)(void) = (void *) KSEG1ADDR(&__rm7k_sc_enable);
-
-        if (read_c0_config() & 0x08)                    /* CONF_SE */
+        if (read_c0_config() & R7K_CONF_SE)
                 return;
 
         printk(KERN_INFO "Enabling secondary cache...");
-        func();
+        run_uncached(__rm7k_sc_enable);
 }
 
 static void rm7k_sc_disable(void)
 {
-        clear_c0_config(1<<3);                          /* CONF_SE */
+        clear_c0_config(R7K_CONF_SE);
 }
 
 struct bcache_ops rm7k_sc_ops = {
@@ -164,7 +151,7 @@ void __init rm7k_sc_init(void)
         printk(KERN_INFO "Secondary cache size %dK, linesize %d bytes.\n",
                (scache_size >> 10), sc_lsize);
 
-        if (!((config >> 3) & 1))       /* CONF_SE */
+        if (!(config & R7K_CONF_SE))
                 rm7k_sc_enable();
 
         /*
diff --git a/include/asm-mips/cacheflush.h b/include/asm-mips/cacheflush.h
index 4213d2c8bb8a..a18ba2edc0b6 100644
--- a/include/asm-mips/cacheflush.h
+++ b/include/asm-mips/cacheflush.h
@@ -90,4 +90,7 @@ extern void (*flush_data_cache_page)(unsigned long addr);
 #define ClearPageDcacheDirty(page)      \
         clear_bit(PG_dcache_dirty, &(page)->flags)
 
+/* Run kernel code uncached, useful for cache probing functions. */
+unsigned long __init run_uncached(void *func);
+
 #endif /* _ASM_CACHEFLUSH_H */
diff --git a/include/asm-mips/mipsregs.h b/include/asm-mips/mipsregs.h
index 006354ed2e29..f3b0b4181508 100644
--- a/include/asm-mips/mipsregs.h
+++ b/include/asm-mips/mipsregs.h
@@ -433,6 +433,9 @@
 #define R5K_CONF_SE             (_ULCAST_(1) << 12)
 #define R5K_CONF_SS             (_ULCAST_(3) << 20)
 
+/* Bits specific to the RM7000.  */
+#define R7K_CONF_SE             (_ULCAST_(1) << 3)
+
 /* Bits specific to the R10000.  */
 #define R10K_CONF_DN            (_ULCAST_(3) <<  3)
 #define R10K_CONF_CT            (_ULCAST_(1) <<  5)