[PATCH] xtensa: Architecture support for Tensilica Xtensa Part 6

The attached patches provides part 6 of an architecture implementation for the
Tensilica Xtensa CPU series.

Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 330 insertions, 0 deletions

diff --git a/include/asm-xtensa/mmu_context.h b/include/asm-xtensa/mmu_context.h
new file mode 100644
index 000000000000..1b0801548cd9
--- /dev/null
+++ b/include/asm-xtensa/mmu_context.h
@@ -0,0 +1,330 @@
+/*
+ * include/asm-xtensa/mmu_context.h
+ *
+ * Switch an MMU context.
+ *
+ * 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) 2001 - 2005 Tensilica Inc.
+ */
+
+#ifndef _XTENSA_MMU_CONTEXT_H
+#define _XTENSA_MMU_CONTEXT_H
+
+#include <linux/config.h>
+#include <linux/stringify.h>
+
+#include <asm/pgtable.h>
+#include <asm/mmu_context.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+/*
+ * Linux was ported to Xtensa assuming all auto-refill ways in set 0
+ * had the same properties (a very likely assumption).  Multiple sets
+ * of auto-refill ways will still work properly, but not as optimally
+ * as the Xtensa designer may have assumed.
+ *
+ * We make this case a hard #error, killing the kernel build, to alert
+ * the developer to this condition (which is more likely an error).
+ * You super-duper clever developers can change it to a warning or
+ * remove it altogether if you think you know what you're doing.  :)
+ */
+
+#if (XCHAL_HAVE_TLBS != 1)
+# error "Linux must have an MMU!"
+#endif
+
+#if ((XCHAL_ITLB_ARF_WAYS == 0) || (XCHAL_DTLB_ARF_WAYS == 0))
+# error "MMU must have auto-refill ways"
+#endif
+
+#if ((XCHAL_ITLB_ARF_SETS != 1) || (XCHAL_DTLB_ARF_SETS != 1))
+# error Linux may not use all auto-refill ways as efficiently as you think
+#endif
+
+#if (XCHAL_MMU_MAX_PTE_PAGE_SIZE != XCHAL_MMU_MIN_PTE_PAGE_SIZE)
+# error Only one page size allowed!
+#endif
+
+extern unsigned long asid_cache;
+extern pgd_t *current_pgd;
+
+/*
+ * Define the number of entries per auto-refill way in set 0 of both I and D
+ * TLBs.  We deal only with set 0 here (an assumption further explained in
+ * assertions.h).  Also, define the total number of ARF entries in both TLBs.
+ */
+
+#define ITLB_ENTRIES_PER_ARF_WAY  (XCHAL_ITLB_SET(XCHAL_ITLB_ARF_SET0,ENTRIES))
+#define DTLB_ENTRIES_PER_ARF_WAY  (XCHAL_DTLB_SET(XCHAL_DTLB_ARF_SET0,ENTRIES))
+
+#define ITLB_ENTRIES                                                    \
+        (ITLB_ENTRIES_PER_ARF_WAY * (XCHAL_ITLB_SET(XCHAL_ITLB_ARF_SET0,WAYS)))
+#define DTLB_ENTRIES                                                    \
+        (DTLB_ENTRIES_PER_ARF_WAY * (XCHAL_DTLB_SET(XCHAL_DTLB_ARF_SET0,WAYS)))
+
+
+/*
+ * SMALLEST_NTLB_ENTRIES is the smaller of ITLB_ENTRIES and DTLB_ENTRIES.
+ * In practice, they are probably equal.  This macro simplifies function
+ * flush_tlb_range().
+ */
+
+#if (DTLB_ENTRIES < ITLB_ENTRIES)
+# define SMALLEST_NTLB_ENTRIES  DTLB_ENTRIES
+#else
+# define SMALLEST_NTLB_ENTRIES  ITLB_ENTRIES
+#endif
+
+
+/*
+ * asid_cache tracks only the ASID[USER_RING] field of the RASID special
+ * register, which is the current user-task asid allocation value.
+ * mm->context has the same meaning.  When it comes time to write the
+ * asid_cache or mm->context values to the RASID special register, we first
+ * shift the value left by 8, then insert the value.
+ * ASID[0] always contains the kernel's asid value, and we reserve three
+ * other asid values that we never assign to user tasks.
+ */
+
+#define ASID_INC        0x1
+#define ASID_MASK       ((1 << XCHAL_MMU_ASID_BITS) - 1)
+
+/*
+ * XCHAL_MMU_ASID_INVALID is a configurable Xtensa processor constant
+ * indicating invalid address space.  XCHAL_MMU_ASID_KERNEL is a configurable
+ * Xtensa processor constant indicating the kernel address space.  They can
+ * be arbitrary values.
+ *
+ * We identify three more unique, reserved ASID values to use in the unused
+ * ring positions.  No other user process will be assigned these reserved
+ * ASID values.
+ *
+ * For example, given that
+ *
+ *      XCHAL_MMU_ASID_INVALID == 0
+ *      XCHAL_MMU_ASID_KERNEL  == 1
+ *
+ * the following maze of #if statements would generate
+ *
+ *      ASID_RESERVED_1        == 2
+ *      ASID_RESERVED_2        == 3
+ *      ASID_RESERVED_3        == 4
+ *      ASID_FIRST_NONRESERVED == 5
+ */
+
+#if (XCHAL_MMU_ASID_INVALID != XCHAL_MMU_ASID_KERNEL + 1)
+# define ASID_RESERVED_1         ((XCHAL_MMU_ASID_KERNEL + 1) & ASID_MASK)
+#else
+# define ASID_RESERVED_1         ((XCHAL_MMU_ASID_KERNEL + 2) & ASID_MASK)
+#endif
+
+#if (XCHAL_MMU_ASID_INVALID != ASID_RESERVED_1 + 1)
+# define ASID_RESERVED_2         ((ASID_RESERVED_1 + 1) & ASID_MASK)
+#else
+# define ASID_RESERVED_2         ((ASID_RESERVED_1 + 2) & ASID_MASK)
+#endif
+
+#if (XCHAL_MMU_ASID_INVALID != ASID_RESERVED_2 + 1)
+# define ASID_RESERVED_3         ((ASID_RESERVED_2 + 1) & ASID_MASK)
+#else
+# define ASID_RESERVED_3         ((ASID_RESERVED_2 + 2) & ASID_MASK)
+#endif
+
+#if (XCHAL_MMU_ASID_INVALID != ASID_RESERVED_3 + 1)
+# define ASID_FIRST_NONRESERVED  ((ASID_RESERVED_3 + 1) & ASID_MASK)
+#else
+# define ASID_FIRST_NONRESERVED  ((ASID_RESERVED_3 + 2) & ASID_MASK)
+#endif
+
+#define ASID_ALL_RESERVED ( ((ASID_RESERVED_1) << 24) + \
+                            ((ASID_RESERVED_2) << 16) + \
+                            ((ASID_RESERVED_3) <<  8) + \
+                            ((XCHAL_MMU_ASID_KERNEL))   )
+
+
+/*
+ * NO_CONTEXT is the invalid ASID value that we don't ever assign to
+ * any user or kernel context.  NO_CONTEXT is a better mnemonic than
+ * XCHAL_MMU_ASID_INVALID, so we use it in code instead.
+ */
+
+#define NO_CONTEXT   XCHAL_MMU_ASID_INVALID
+
+#if (KERNEL_RING != 0)
+# error The KERNEL_RING really should be zero.
+#endif
+
+#if (USER_RING >= XCHAL_MMU_RINGS)
+# error USER_RING cannot be greater than the highest numbered ring.
+#endif
+
+#if (USER_RING == KERNEL_RING)
+# error The user and kernel rings really should not be equal.
+#endif
+
+#if (USER_RING == 1)
+#define ASID_INSERT(x) ( ((ASID_RESERVED_1)   << 24) + \
+                         ((ASID_RESERVED_2)   << 16) + \
+                         (((x) & (ASID_MASK)) <<  8) + \
+                         ((XCHAL_MMU_ASID_KERNEL))   )
+
+#elif (USER_RING == 2)
+#define ASID_INSERT(x) ( ((ASID_RESERVED_1)   << 24) + \
+                         (((x) & (ASID_MASK)) << 16) + \
+                         ((ASID_RESERVED_2)   <<  8) + \
+                         ((XCHAL_MMU_ASID_KERNEL))   )
+
+#elif (USER_RING == 3)
+#define ASID_INSERT(x) ( (((x) & (ASID_MASK)) << 24) + \
+                         ((ASID_RESERVED_1)   << 16) + \
+                         ((ASID_RESERVED_2)   <<  8) + \
+                         ((XCHAL_MMU_ASID_KERNEL))   )
+
+#else
+#error Goofy value for USER_RING
+
+#endif /* USER_RING == 1 */
+
+
+/*
+ *  All unused by hardware upper bits will be considered
+ *  as a software asid extension.
+ */
+
+#define ASID_VERSION_MASK  ((unsigned long)~(ASID_MASK|(ASID_MASK-1)))
+#define ASID_FIRST_VERSION                                              \
+        ((unsigned long)(~ASID_VERSION_MASK) + 1 + ASID_FIRST_NONRESERVED)
+
+extern inline void set_rasid_register (unsigned long val)
+{
+        __asm__ __volatile__ (" wsr %0, "__stringify(RASID)"\n\t"
+                              " isync\n" : : "a" (val));
+}
+
+extern inline unsigned long get_rasid_register (void)
+{
+        unsigned long tmp;
+        __asm__ __volatile__ (" rsr %0, "__stringify(RASID)"\n\t" : "=a" (tmp));
+        return tmp;
+}
+
+
+#if ((XCHAL_MMU_ASID_INVALID == 0) && (XCHAL_MMU_ASID_KERNEL == 1))
+
+extern inline void
+get_new_mmu_context(struct mm_struct *mm, unsigned long asid)
+{
+        extern void flush_tlb_all(void);
+        if (! ((asid += ASID_INC) & ASID_MASK) ) {
+                flush_tlb_all(); /* start new asid cycle */
+                if (!asid)      /* fix version if needed */
+                        asid = ASID_FIRST_VERSION - ASID_FIRST_NONRESERVED;
+                asid += ASID_FIRST_NONRESERVED;
+        }
+        mm->context = asid_cache = asid;
+}
+
+#else
+#warning ASID_{INVALID,KERNEL} values impose non-optimal get_new_mmu_context implementation
+
+/* XCHAL_MMU_ASID_INVALID == 0 and XCHAL_MMU_ASID_KERNEL ==1 are
+   really the best, but if you insist... */
+
+extern inline int validate_asid (unsigned long asid)
+{
+        switch (asid) {
+        case XCHAL_MMU_ASID_INVALID:
+        case XCHAL_MMU_ASID_KERNEL:
+        case ASID_RESERVED_1:
+        case ASID_RESERVED_2:
+        case ASID_RESERVED_3:
+                return 0; /* can't use these values as ASIDs */
+        }
+        return 1; /* valid */
+}
+
+extern inline void
+get_new_mmu_context(struct mm_struct *mm, unsigned long asid)
+{
+        extern void flush_tlb_all(void);
+        while (1) {
+                asid += ASID_INC;
+                if ( ! (asid & ASID_MASK) ) {
+                        flush_tlb_all(); /* start new asid cycle */
+                        if (!asid)      /* fix version if needed */
+                                asid = ASID_FIRST_VERSION - ASID_FIRST_NONRESERVED;
+                        asid += ASID_FIRST_NONRESERVED;
+                        break; /* no need to validate here */
+                }
+                if (validate_asid (asid & ASID_MASK))
+                        break;
+        }
+        mm->context = asid_cache = asid;
+}
+
+#endif
+
+
+/*
+ * Initialize the context related info for a new mm_struct
+ * instance.
+ */
+
+extern inline int
+init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+        mm->context = NO_CONTEXT;
+        return 0;
+}
+
+extern inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+                             struct task_struct *tsk)
+{
+        unsigned long asid = asid_cache;
+
+        /* Check if our ASID is of an older version and thus invalid */
+
+        if ((next->context ^ asid) & ASID_VERSION_MASK)
+                get_new_mmu_context(next, asid);
+
+        set_rasid_register (ASID_INSERT(next->context));
+        invalidate_page_directory();
+}
+
+#define deactivate_mm(tsk, mm)  do { } while(0)
+
+/*
+ * Destroy context related info for an mm_struct that is about
+ * to be put to rest.
+ */
+extern inline void destroy_context(struct mm_struct *mm)
+{
+        /* Nothing to do. */
+}
+
+/*
+ * After we have set current->mm to a new value, this activates
+ * the context for the new mm so we see the new mappings.
+ */
+extern inline void
+activate_mm(struct mm_struct *prev, struct mm_struct *next)
+{
+        /* Unconditionally get a new ASID.  */
+
+        get_new_mmu_context(next, asid_cache);
+        set_rasid_register (ASID_INSERT(next->context));
+        invalidate_page_directory();
+}
+
+
+static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+        /* Nothing to do. */
+
+}
+
+#endif /* _XTENSA_MMU_CONTEXT_H */