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    Subject[PATCH 4/8] powerpc/8xx: remove unused _PAGE_WRITETHRU
    Date
    _PAGE_WRITETHRU is only used in:
    * AMIGA_Z2RAM block driver which is never activated on powerPC
    * Video/FB driver which is for PPC_PMAC

    Therefore, no need to spend time in 8xx TLB miss handlers for
    handling it.

    And by removing it, we free up bit 20 which then avoids having
    to clear it on each TLB miss.

    Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
    ---
    arch/powerpc/include/asm/nohash/32/pte-8xx.h | 3 +--
    arch/powerpc/include/asm/nohash/pgtable.h | 2 ++
    arch/powerpc/kernel/head_8xx.S | 5 -----
    3 files changed, 3 insertions(+), 7 deletions(-)

    diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
    index 6dc0180fd5c7..19a5ecaef265 100644
    --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
    +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
    @@ -41,8 +41,7 @@
    #define _PAGE_GUARDED 0x0010 /* Copied to L1 G entry in DTLB */
    #define _PAGE_USER 0x0020 /* Copied to L1 APG lsb */
    #define _PAGE_EXEC 0x0040 /* Copied to L1 APG */
    -#define _PAGE_WRITETHRU 0x0080 /* software: caching is write through */
    -#define _PAGE_ACCESSED 0x0800 /* software: page referenced */
    +#define _PAGE_ACCESSED 0x0080 /* software: page referenced */

    #define _PAGE_RO 0x0600 /* Supervisor RO, User no access */

    diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
    index 5c68f4a59f75..84120d65d0e9 100644
    --- a/arch/powerpc/include/asm/nohash/pgtable.h
    +++ b/arch/powerpc/include/asm/nohash/pgtable.h
    @@ -212,8 +212,10 @@ extern int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long addre
    #define pgprot_cached(prot) (__pgprot((pgprot_val(prot) & ~_PAGE_CACHE_CTL) | \
    _PAGE_COHERENT))

    +#if _PAGE_WRITETHRU != 0
    #define pgprot_cached_wthru(prot) (__pgprot((pgprot_val(prot) & ~_PAGE_CACHE_CTL) | \
    _PAGE_COHERENT | _PAGE_WRITETHRU))
    +#endif

    #define pgprot_cached_noncoherent(prot) \
    (__pgprot(pgprot_val(prot) & ~_PAGE_CACHE_CTL))
    diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
    index 641c9a9d4db2..6399dcadf51d 100644
    --- a/arch/powerpc/kernel/head_8xx.S
    +++ b/arch/powerpc/kernel/head_8xx.S
    @@ -486,10 +486,6 @@ _ENTRY(DTLBMiss_jmp)
    * above.
    */
    rlwimi r11, r10, 0, 26, 27
    - /* Insert the WriteThru flag into the TWC from the Linux PTE.
    - * It is bit 25 in the Linux PTE and bit 30 in the TWC
    - */
    - rlwimi r11, r10, 32-5, 30, 30
    mtspr SPRN_MD_TWC, r11

    /* In 4k pages mode, SPS (bit 28) in RPN must match PS[1] (bit 29)
    @@ -523,7 +519,6 @@ _ENTRY(DTLBMiss_jmp)
    #else
    rlwimi r10, r11, 0, 24, 28 /* Set 24-27, clear 28 */
    #endif
    - rlwimi r10, r11, 0, 20, 20 /* clear 20 */
    mtspr SPRN_MD_RPN, r10 /* Update TLB entry */

    /* Restore registers */
    --
    2.13.3
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