arch/powerpc/include/asm/pte-8xx.h

   1 #ifndef _ASM_POWERPC_PTE_8xx_H
   2 #define _ASM_POWERPC_PTE_8xx_H
   3 #ifdef __KERNEL__
   4
   5 /*
   6  * The PowerPC MPC8xx uses a TLB with hardware assisted, software tablewalk.
   7  * We also use the two level tables, but we can put the real bits in them
   8  * needed for the TLB and tablewalk.  These definitions require Mx_CTR.PPM = 0,
   9  * Mx_CTR.PPCS = 0, and MD_CTR.TWAM = 1.  The level 2 descriptor has
  10  * additional page protection (when Mx_CTR.PPCS = 1) that allows TLB hit
  11  * based upon user/super access.  The TLB does not have accessed nor write
  12  * protect.  We assume that if the TLB get loaded with an entry it is
  13  * accessed, and overload the changed bit for write protect.  We use
  14  * two bits in the software pte that are supposed to be set to zero in
  15  * the TLB entry (24 and 25) for these indicators.  Although the level 1
  16  * descriptor contains the guarded and writethrough/copyback bits, we can
  17  * set these at the page level since they get copied from the Mx_TWC
  18  * register when the TLB entry is loaded.  We will use bit 27 for guard, since
  19  * that is where it exists in the MD_TWC, and bit 26 for writethrough.
  20  * These will get masked from the level 2 descriptor at TLB load time, and
  21  * copied to the MD_TWC before it gets loaded.
  22  * Large page sizes added.  We currently support two sizes, 4K and 8M.
  23  * This also allows a TLB hander optimization because we can directly
  24  * load the PMD into MD_TWC.  The 8M pages are only used for kernel
  25  * mapping of well known areas.  The PMD (PGD) entries contain control
  26  * flags in addition to the address, so care must be taken that the
  27  * software no longer assumes these are only pointers.
  28  */
  29
  30 /* Definitions for 8xx embedded chips. */
  31 #define _PAGE_PRESENT   0x0001  /* Page is valid */
  32 #define _PAGE_FILE      0x0002  /* when !present: nonlinear file mapping */
  33 #define _PAGE_NO_CACHE  0x0002  /* I: cache inhibit */
  34 #define _PAGE_SHARED    0x0004  /* No ASID (context) compare */
  35 #define _PAGE_SPECIAL   0x0008  /* SW entry, forced to 0 by the TLB miss */
  36
  37 /* These five software bits must be masked out when the entry is loaded
  38  * into the TLB.
  39  */
  40 #define _PAGE_GUARDED   0x0010  /* software: guarded access */
  41 #define _PAGE_DIRTY     0x0020  /* software: page changed */
  42 #define _PAGE_RW        0x0040  /* software: user write access allowed */
  43 #define _PAGE_ACCESSED  0x0080  /* software: page referenced */
  44
  45 /* Setting any bits in the nibble with the follow two controls will
  46  * require a TLB exception handler change.  It is assumed unused bits
  47  * are always zero.
  48  */
  49 #define _PAGE_HWWRITE   0x0100  /* h/w write enable: never set in Linux PTE */
  50 #define _PAGE_USER      0x0800  /* One of the PP bits, the other is USER&~RW */
  51
  52 #define _PMD_PRESENT    0x0001
  53 #define _PMD_BAD        0x0ff0
  54 #define _PMD_PAGE_MASK  0x000c
  55 #define _PMD_PAGE_8M    0x000c
  56
  57 #define _PTE_NONE_MASK _PAGE_ACCESSED
  58
  59 /* Until my rework is finished, 8xx still needs atomic PTE updates */
  60 #define PTE_ATOMIC_UPDATES      1
  61
  62 /* We need to add _PAGE_SHARED to kernel pages */
  63 #define _PAGE_KERNEL_RO (_PAGE_SHARED)
  64 #define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
  65
  66 #endif /* __KERNEL__ */
  67 #endif /*  _ASM_POWERPC_PTE_8xx_H */