Eric Lee / smarc-fsl-linux-kernel

04 Jul, 2014

1 commit

  • 3a044178c   readq/writeq: Add explicit lo_hi_[read|write]_q and hi_lo_[read|write]_q ... Browse Code »

    Even on x86-64, I've found the need to break up a readq() into 2 readl()
    calls. According to the Intel datasheet for the E3-1200 processor:

    "
    Software must not access B0/D0/F0 32-bit memory-mapped registers with
    requests that cross a DW boundary.
    "

    (http://www.intel.com/content/www/us/en/processors/xeon/xeon-e3-1200-family-vol-2-datasheet.html p. 16)

    I can confirm this is true via several hard machine lockups.

    Thus, add explicit hi_lo_[readq|write]_q and lo_hi_[read|write]_q so that these
    uses are spelled out.

    Signed-off-by: Jason Baron
    Link: http://lkml.kernel.org/r/281f09da7ad01e5cea99737ec34d2399bdbbbf63.1403818526.git.jbaron@akamai.com
    Signed-off-by: Borislav Petkov

    Jason Baron
     

22 Feb, 2012

1 commit

  • 797a796a1   asm-generic: architecture independent readq/writeq for 32bit environment ... Browse Code »

    This provides unified readq()/writeq() helper functions for 32-bit
    drivers.

    For some cases, readq/writeq without atomicity is harmful, and order of
    io access has to be specified explicitly. So in this patch, new two
    header files which contain non-atomic readq/writeq are added.

    - provides non-atomic readq/
    writeq with the order of lower address -> higher address

    - provides non-atomic readq/
    writeq with reversed order

    This allows us to remove some readq()s that were added drivers when the
    default non-atomic ones were removed in commit dbee8a0affd5 ("x86:
    remove 32-bit versions of readq()/writeq()")

    The drivers which need readq/writeq but can do with the non-atomic ones
    must add the line:

    #include /* or hi-lo.h */

    But this will be nop in 64-bit environments, and no other #ifdefs are
    required. So I believe that this patch can solve the problem of
    1. driver-specific readq/writeq
    2. atomicity and order of io access

    This patch is tested with building allyesconfig and allmodconfig as
    ARCH=x86 and ARCH=i386 on top of tip/master.

    Cc: Kashyap Desai
    Cc: Len Brown
    Cc: Ravi Anand
    Cc: Vikas Chaudhary
    Cc: Matthew Garrett
    Cc: Jason Uhlenkott
    Cc: James Bottomley
    Cc: Thomas Gleixner
    Cc: "H. Peter Anvin"
    Cc: Roland Dreier
    Cc: James Bottomley
    Cc: Alan Cox
    Cc: Matthew Wilcox
    Cc: Andrew Morton
    Signed-off-by: Hitoshi Mitake
    Signed-off-by: Linus Torvalds

    Hitoshi Mitake