Messages in this thread | | | Date | Mon, 17 Dec 2007 16:02:20 -0500 | From | "David P. Reed" <> | Subject | Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override. |
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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.
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