arch/powerpc/include/asm/nohash/32/pte-44x.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_POWERPC_NOHASH_32_PTE_44x_H
   3 #define _ASM_POWERPC_NOHASH_32_PTE_44x_H
   4 #ifdef __KERNEL__
   5
   6 /*
   7  * Definitions for PPC440
   8  *
   9  * Because of the 3 word TLB entries to support 36-bit addressing,
  10  * the attribute are difficult to map in such a fashion that they
  11  * are easily loaded during exception processing.  I decided to
  12  * organize the entry so the ERPN is the only portion in the
  13  * upper word of the PTE and the attribute bits below are packed
  14  * in as sensibly as they can be in the area below a 4KB page size
  15  * oriented RPN.  This at least makes it easy to load the RPN and
  16  * ERPN fields in the TLB. -Matt
  17  *
  18  * This isn't entirely true anymore, at least some bits are now
  19  * easier to move into the TLB from the PTE. -BenH.
  20  *
  21  * Note that these bits preclude future use of a page size
  22  * less than 4KB.
  23  *
  24  *
  25  * PPC 440 core has following TLB attribute fields;
  26  *
  27  *   TLB1:
  28  *   0  1  2  3  4  ... 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
  29  *   RPN.................................  -  -  -  -  -  - ERPN.......
  30  *
  31  *   TLB2:
  32  *   0  1  2  3  4  ... 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
  33  *   -  -  -  -  -    - U0 U1 U2 U3 W  I  M  G  E   - UX UW UR SX SW SR
  34  *
  35  * Newer 440 cores (440x6 as used on AMCC 460EX/460GT) have additional
  36  * TLB2 storage attribute fields. Those are:
  37  *
  38  *   TLB2:
  39  *   0...10    11   12   13   14   15   16...31
  40  *   no change WL1  IL1I IL1D IL2I IL2D no change
  41  *
  42  * There are some constrains and options, to decide mapping software bits
  43  * into TLB entry.
  44  *
  45  *   - PRESENT *must* be in the bottom three bits because swap cache
  46  *     entries use the top 29 bits for TLB2.
  47  *
  48  *   - CACHE COHERENT bit (M) has no effect on original PPC440 cores,
  49  *     because it doesn't support SMP. However, some later 460 variants
  50  *     have -some- form of SMP support and so I keep the bit there for
  51  *     future use
  52  *
  53  * With the PPC 44x Linux implementation, the 0-11th LSBs of the PTE are used
  54  * for memory protection related functions (see PTE structure in
  55  * include/asm-ppc/mmu.h).  The _PAGE_XXX definitions in this file map to the
  56  * above bits.  Note that the bit values are CPU specific, not architecture
  57  * specific.
  58  *
  59  * The kernel PTE entry holds an arch-dependent swp_entry structure under
  60  * certain situations. In other words, in such situations some portion of
  61  * the PTE bits are used as a swp_entry. In the PPC implementation, the
  62  * 3-24th LSB are shared with swp_entry, however the 0-2nd three LSB still
  63  * hold protection values. That means the three protection bits are
  64  * reserved for both PTE and SWAP entry at the most significant three
  65  * LSBs.
  66  *
  67  * There are three protection bits available for SWAP entry:
  68  *      _PAGE_PRESENT
  69  *      _PAGE_HASHPTE (if HW has)
  70  *
  71  * So those three bits have to be inside of 0-2nd LSB of PTE.
  72  *
  73  */
  74
  75 #define _PAGE_PRESENT   0x00000001              /* S: PTE valid */
  76 #define _PAGE_RW        0x00000002              /* S: Write permission */
  77 #define _PAGE_EXEC      0x00000004              /* H: Execute permission */
  78 #define _PAGE_ACCESSED  0x00000008              /* S: Page referenced */
  79 #define _PAGE_DIRTY     0x00000010              /* S: Page dirty */
  80 #define _PAGE_SPECIAL   0x00000020              /* S: Special page */
  81 #define _PAGE_USER      0x00000040              /* S: User page */
  82 #define _PAGE_ENDIAN    0x00000080              /* H: E bit */
  83 #define _PAGE_GUARDED   0x00000100              /* H: G bit */
  84 #define _PAGE_COHERENT  0x00000200              /* H: M bit */
  85 #define _PAGE_NO_CACHE  0x00000400              /* H: I bit */
  86 #define _PAGE_WRITETHRU 0x00000800              /* H: W bit */
  87
  88 /* TODO: Add large page lowmem mapping support */
  89 #define _PMD_PRESENT    0
  90 #define _PMD_PRESENT_MASK (PAGE_MASK)
  91 #define _PMD_BAD        (~PAGE_MASK)
  92
  93 /* ERPN in a PTE never gets cleared, ignore it */
  94 #define _PTE_NONE_MASK  0xffffffff00000000ULL
  95
  96
  97 #endif /* __KERNEL__ */
  98 #endif /*  _ASM_POWERPC_NOHASH_32_PTE_44x_H */