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>

1 files changed, 76 insertions, 0 deletions

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;
+}