Messages in this thread Patch in this message | | | From | "Dunlap, Randy" <> | Subject | RE: A20 gate control question. | Date | Mon, 17 Jul 2000 09:46:17 -0700 |
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> Hi.
Jesse Off (joff@newmonics.com) posted a patch to do this on Oct. 26, 1999. His patch needs to be added to setup.S IMO, along with the current gating of A20.
<from joff:> The company I work for, NewMonics, does a lot of work on embedded systems and we've recently ported our product (a lightweight realtime Java virtual machine) to Linux. On some of the embedded systems/PLC's we work with (specifically, those based on the AMD Elan SC310 and SC300 386 microcontrollers) Linux fails to boot because the keyboard controller is not there to set the A20 bit. These machines are headless, keyboardless, and diskless (except for a small PCMCIA flash card). With the following patch, we were able to get our virtual machine running on Linux under this hardware via a serial port console.
--- setup.S Mon Aug 9 12:04:38 1999 +++ setup.S.patched Tue Oct 26 10:50:36 1999 @@ -553,6 +553,15 @@ out #0x60,al call empty_8042 +! The AMD 386 Elan SC300 and SC310 microcontrollers which +! are used in some embedded systems don't have +! a keyboard controller; we have to do things different on +! these chips. Jesse Off, NewMonics, Inc. <joff@newmonics.com> + + mov al,#0x2 ! GATEA20 functionality is acheived + out #0x92, al ! via port 0x92, bit 1. + + ! wait until a20 really *is* enabled; it can take a fair amount of ! time on certain systems; Toshiba Tecras are known to have this ! problem. The memory location used here is the int 0x1f vector, - </from joff>
This applies to newer Intel systems also. I asked internally if port 0x92 might have conflicts with other chipsets and the answer I got was "no."
Also, from other email on this subject, is there an implication here that the timeout (counter) in "empty_8042" doesn't work (on systems that don't have an 8042 controller)?
~Randy ___________________________________________________ |Randy Dunlap Intel Corp., DAL Sr. SW Engr.| |randy.dunlap.at.intel.com 503-696-2055| |NOTE: Any views presented here are mine alone | |and may not represent the views of my employer. | |_________________________________________________| > -----Original Message----- > From: Agust Karlsson [mailto:Gusti@pallas.dk] > Sent: Friday, July 14, 2000 5:46 AM > To: 'linux-kernel@vger.rutgers.edu'; 'linux-config@vger.rutgers.edu' > Subject: A20 gate control question. > > Where does Linux set the System Control Port A (io port 0x92) or where > should I put the code to use port 0x92 as a a20 gate handler. > > Best regards > > Agust Karlsson > Pallas Informatik > Allerød Denmark > > -
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