lkml.org 
[lkml]   [2007]   [Dec]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.


    H. Peter Anvin wrote:
    > David P. Reed wrote:
    >> As support: port 80 on the reporter's (my) HP dv9000z laptop clearly
    >> responds to reads differently than "unused" ports. In particular, an
    >> inb takes 1/2 the elapsed time compared to a read to "known" unused
    >> port 0xed - 792 tsc ticks for port 80 compared to about 1450 tsc
    >> ticks for port 0xed and other unused ports (tsc at 800 MHz).
    >>
    >
    > Any timings for port 0xf0 (write zero), out of curiosity?
    >

    Here's a bunch of data:

    port 0xF0: cycles: out 919, in 933
    port 0xed: cycles: out 2541, in 2036
    port 0x70: cycles: out n/a, in 934
    port 0x80: cycles: out 1424, in 795

    AMD Turion 64x2 TL-60 CPU running at 800 MHz, nVidia MCP51 chipset,
    Quanta motherboard. Running 2.6.24-rc5 with Ingo's patch so inb_p, etc.
    use port 0xed.

    Note that I can run the port 80 test once, the second time I get the
    hard freeze. I didn't try writing to port 70 from userspace - that
    one's dangerous, but the reading of it was included for a timing typical
    of a chipset supported device. These are all pretty consistent.

    I find the "read" timing from 0x80 verrrrry interesting. The write
    timeing is also interesting, being faster than an unused port.




    \
     
     \ /
      Last update: 2007-12-17 22:05    [W:4.204 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site