From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933463AbXGKT0n (ORCPT ); Wed, 11 Jul 2007 15:26:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932629AbXGKTTm (ORCPT ); Wed, 11 Jul 2007 15:19:42 -0400 Received: from terminus.zytor.com ([192.83.249.54]:38289 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762113AbXGKTTd (ORCPT ); Wed, 11 Jul 2007 15:19:33 -0400 From: "H. Peter Anvin" To: torvalds@linux-foundation.org, andi@firstfloor.org, linux-kernel@vger.kernel.org Cc: "H. Peter Anvin" Subject: [x86 setup 17/33] A20 handling code Date: Wed, 11 Jul 2007 12:18:42 -0700 Message-Id: <11841815411436-git-send-email-hpa@zytor.com> X-Mailer: git-send-email 1.5.2.2 In-Reply-To: <1184181541746-git-send-email-hpa@zytor.com> References: <1184181538674-git-send-email-hpa@zytor.com> <118418153862-git-send-email-hpa@zytor.com> <11841815382283-git-send-email-hpa@zytor.com> <11841815392122-git-send-email-hpa@zytor.com> <11841815393975-git-send-email-hpa@zytor.com> <11841815393014-git-send-email-hpa@zytor.com> <1184181539416-git-send-email-hpa@zytor.com> <118418153972-git-send-email-hpa@zytor.com> <11841815391923-git-send-email-hpa@zytor.com> <11841815403678-git-send-email-hpa@zytor.com> <11841815403041-git-send-email-hpa@zytor.com> <11841815402349-git-send-email-hpa@zytor.com> <11841815401013-git-send-email-hpa@zytor.com> <1184181540369-git-send-email-hpa@zytor.com> <11841815401476-git-send-email-hpa@zytor.com> <11841815411443-git-send-email-hpa@zytor.com> <1184181541746-git-send-email-hpa@zytor.com> Message-Id: In-Reply-To: <7aca4ce0a222438c94300a2ea535270a21db8812.1184181208.git.hpa@zytor.com> References: <7aca4ce0a222438c94300a2ea535270a21db8812.1184181208.git.hpa@zytor.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: H. Peter Anvin A20 handling code for the new x86 setup code. This implements the same algorithms as the assembly version. Signed-off-by: H. Peter Anvin --- arch/i386/boot/a20.c | 161 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 161 insertions(+), 0 deletions(-) create mode 100644 arch/i386/boot/a20.c diff --git a/arch/i386/boot/a20.c b/arch/i386/boot/a20.c new file mode 100644 index 0000000..31348d0 --- /dev/null +++ b/arch/i386/boot/a20.c @@ -0,0 +1,161 @@ +/* -*- linux-c -*- ------------------------------------------------------- * + * + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright 2007 rPath, Inc. - All Rights Reserved + * + * This file is part of the Linux kernel, and is made available under + * the terms of the GNU General Public License version 2. + * + * ----------------------------------------------------------------------- */ + +/* + * arch/i386/boot/a20.c + * + * Enable A20 gate (return -1 on failure) + */ + +#include "boot.h" + +#define MAX_8042_LOOPS 100000 + +static int empty_8042(void) +{ + u8 status; + int loops = MAX_8042_LOOPS; + + while (loops--) { + io_delay(); + + status = inb(0x64); + if (status & 1) { + /* Read and discard input data */ + io_delay(); + (void)inb(0x60); + } else if (!(status & 2)) { + /* Buffers empty, finished! */ + return 0; + } + } + + return -1; +} + +/* Returns nonzero if the A20 line is enabled. The memory address + used as a test is the int $0x80 vector, which should be safe. */ + +#define A20_TEST_ADDR (4*0x80) +#define A20_TEST_SHORT 32 +#define A20_TEST_LONG 2097152 /* 2^21 */ + +static int a20_test(int loops) +{ + int ok = 0; + int saved, ctr; + + set_fs(0x0000); + set_gs(0xffff); + + saved = ctr = rdfs32(A20_TEST_ADDR); + + while (loops--) { + wrfs32(++ctr, A20_TEST_ADDR); + io_delay(); /* Serialize and make delay constant */ + ok = rdgs32(A20_TEST_ADDR+0x10) ^ ctr; + if (ok) + break; + } + + wrfs32(saved, A20_TEST_ADDR); + return ok; +} + +/* Quick test to see if A20 is already enabled */ +static int a20_test_short(void) +{ + return a20_test(A20_TEST_SHORT); +} + +/* Longer test that actually waits for A20 to come on line; this + is useful when dealing with the KBC or other slow external circuitry. */ +static int a20_test_long(void) +{ + return a20_test(A20_TEST_LONG); +} + +static void enable_a20_bios(void) +{ + asm volatile("pushfl; int $0x15; popfl" + : : "a" ((u16)0x2401)); +} + +static void enable_a20_kbc(void) +{ + empty_8042(); + + outb(0xd1, 0x64); /* Command write */ + empty_8042(); + + outb(0xdf, 0x60); /* A20 on */ + empty_8042(); +} + +static void enable_a20_fast(void) +{ + u8 port_a; + + port_a = inb(0x92); /* Configuration port A */ + port_a |= 0x02; /* Enable A20 */ + port_a &= ~0x01; /* Do not reset machine */ + outb(port_a, 0x92); +} + +/* + * Actual routine to enable A20; return 0 on ok, -1 on failure + */ + +#define A20_ENABLE_LOOPS 255 /* Number of times to try */ + +int enable_a20(void) +{ + int loops = A20_ENABLE_LOOPS; + +#if defined(CONFIG_X86_ELAN) + /* Elan croaks if we try to touch the KBC */ + enable_a20_fast(); + while (!a20_test_long()) + ; + return 0; +#elif defined(CONFIG_X86_VOYAGER) + /* On Voyager, a20_test() is unsafe? */ + enable_a20_kbc(); + return 0; +#else + while (loops--) { + /* First, check to see if A20 is already enabled + (legacy free, etc.) */ + if (a20_test_short()) + return 0; + + /* Next, try the BIOS (INT 0x15, AX=0x2401) */ + enable_a20_bios(); + if (a20_test_short()) + return 0; + + /* Try enabling A20 through the keyboard controller */ + empty_8042(); + if (a20_test_short()) + return 0; /* BIOS worked, but with delayed reaction */ + + enable_a20_kbc(); + if (a20_test_long()) + return 0; + + /* Finally, try enabling the "fast A20 gate" */ + enable_a20_fast(); + if (a20_test_long()) + return 0; + } + + return -1; +#endif +} -- 1.5.2.2