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linux-next/include/asm-mips/sibyte/sb1250.h
Ralf Baechle a904f74785 [MIPS] Sibyte: Fix race in sb1250_gettimeoffset().
From Dave Johnson <djohnson+linuxmips@sw.starentnetworks.com>:
    
sb1250_gettimeoffset() simply reads the current cpu 0 timer remaining
value, however once this counter reaches 0 and the interrupt is raised,
it immediately resets and begins to count down again.
    
If sb1250_gettimeoffset() is called on cpu 1 via do_gettimeofday() after
the timer has reset but prior to cpu 0 processing the interrupt and
taking write_seqlock() in timer_interrupt() it will return a full value
(or close to it) causing time to jump backwards 1ms. Once cpu 0 handles
the interrupt and timer_interrupt() gets far enough along it will jump
forward 1ms.
    
Fix this problem by implementing mips_hpt_*() on sb1250 using a spare
timer unrelated to the existing periodic interrupt timers. It runs at
1Mhz with a full 23bit counter.  This eliminated the custom
do_gettimeoffset() for sb1250 and allowed use of the generic
fixed_rate_gettimeoffset() using mips_hpt_*() and timerhi/timerlo.
    
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2006-03-18 16:59:30 +00:00

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2.1 KiB
C

/*
* Copyright (C) 2000, 2001, 2002, 2003 Broadcom Corporation
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifndef _ASM_SIBYTE_SB1250_H
#define _ASM_SIBYTE_SB1250_H
/*
* yymmddpp: year, month, day, patch.
* should sync with Makefile EXTRAVERSION
*/
#define SIBYTE_RELEASE 0x02111403
#define SB1250_NR_IRQS 64
#define BCM1480_NR_IRQS 128
#define BCM1480_NR_IRQS_HALF 64
#define SB1250_DUART_MINOR_BASE 64
#ifndef __ASSEMBLY__
#include <asm/addrspace.h>
/* For revision/pass information */
#include <asm/sibyte/sb1250_scd.h>
#include <asm/sibyte/bcm1480_scd.h>
extern unsigned int sb1_pass;
extern unsigned int soc_pass;
extern unsigned int soc_type;
extern unsigned int periph_rev;
extern unsigned int zbbus_mhz;
extern void sb1250_hpt_setup(void);
extern void sb1250_time_init(void);
extern void sb1250_mask_irq(int cpu, int irq);
extern void sb1250_unmask_irq(int cpu, int irq);
extern void sb1250_smp_finish(void);
extern void bcm1480_time_init(void);
extern unsigned long bcm1480_gettimeoffset(void);
extern void bcm1480_mask_irq(int cpu, int irq);
extern void bcm1480_unmask_irq(int cpu, int irq);
extern void bcm1480_smp_finish(void);
extern void prom_printf(char *fmt, ...);
#define AT_spin \
__asm__ __volatile__ ( \
".set noat\n" \
"li $at, 0\n" \
"1: beqz $at, 1b\n" \
".set at\n" \
)
#endif
#define IOADDR(a) ((volatile void __iomem *)(IO_BASE + (a)))
#endif