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linux/include/asm-v850/anna.h
H. Peter Anvin bdc807871d avoid overflows in kernel/time.c 
When the conversion factor between jiffies and milli- or microseconds is
not a single multiply or divide, as for the case of HZ == 300, we currently
do a multiply followed by a divide.  The intervening result, however, is
subject to overflows, especially since the fraction is not simplified (for
HZ == 300, we multiply by 300 and divide by 1000).

This is exposed to the user when passing a large timeout to poll(), for
example.

This patch replaces the multiply-divide with a reciprocal multiplication on
32-bit platforms.  When the input is an unsigned long, there is no portable
way to do this on 64-bit platforms there is no portable way to do this
since it requires a 128-bit intermediate result (which gcc does support on
64-bit platforms but may generate libgcc calls, e.g.  on 64-bit s390), but
since the output is a 32-bit integer in the cases affected, just simplify
the multiply-divide (*3/10 instead of *300/1000).

The reciprocal multiply used can have off-by-one errors in the upper half
of the valid output range.  This could be avoided at the expense of having
to deal with a potential 65-bit intermediate result.  Since the intent is
to avoid overflow problems and most of the other time conversions are only
semiexact, the off-by-one errors were considered an acceptable tradeoff.

At Ralf Baechle's suggestion, this version uses a Perl script to compute
the necessary constants.  We already have dependencies on Perl for kernel
compiles.  This does, however, require the Perl module Math::BigInt, which
is included in the standard Perl distribution starting with version 5.8.0.
In order to support older versions of Perl, include a table of canned
constants in the script itself, and structure the script so that
Math::BigInt isn't required if pulling values from said table.

Running the script requires that the HZ value is available from the
Makefile.  Thus, this patch also adds the Kconfig variable CONFIG_HZ to the
architectures which didn't already have it (alpha, cris, frv, h8300, m32r,
m68k, m68knommu, sparc, v850, and xtensa.) It does *not* touch the sh or
sh64 architectures, since Paul Mundt has dealt with those separately in the
sh tree.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
Cc: Sam Ravnborg <sam@ravnborg.org>,
Cc: Paul Mundt <lethal@linux-sh.org>,
Cc: Richard Henderson <rth@twiddle.net>,
Cc: Michael Starvik <starvik@axis.com>,
Cc: David Howells <dhowells@redhat.com>,
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>,
Cc: Hirokazu Takata <takata@linux-m32r.org>,
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Cc: Roman Zippel <zippel@linux-m68k.org>,
Cc: William L. Irwin <sparclinux@vger.kernel.org>,
Cc: Chris Zankel <chris@zankel.net>,
Cc: H. Peter Anvin <hpa@zytor.com>,
Cc: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:39 -08:00

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/*
* include/asm-v850/anna.h -- Anna V850E2 evaluation cpu chip/board
*
* Copyright (C) 2001,02,03 NEC Electronics Corporation
* Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org>
*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file COPYING in the main directory of this
* archive for more details.
*
* Written by Miles Bader <miles@gnu.org>
*/
#ifndef __V850_ANNA_H__
#define __V850_ANNA_H__
#include <asm/v850e2.h> /* Based on V850E2 core. */
#define CPU_MODEL "v850e2/anna"
#define CPU_MODEL_LONG "NEC V850E2/Anna"
#define PLATFORM "anna"
#define PLATFORM_LONG "NEC/Midas lab V850E2/Anna evaluation board"
#define CPU_CLOCK_FREQ 200000000 /* 200MHz */
#define SYS_CLOCK_FREQ 33300000 /* 33.3MHz */
/* 1MB of static RAM. This memory is mirrored 64 times. */
#define SRAM_ADDR 0x04000000
#define SRAM_SIZE 0x00100000 /* 1MB */
/* 64MB of DRAM. */
#define SDRAM_ADDR 0x08000000
#define SDRAM_SIZE 0x04000000 /* 64MB */
/* For <asm/page.h> */
#define PAGE_OFFSET SRAM_ADDR
/* We use on-chip RAM, for a few miscellaneous variables that must be
accessible using a load instruction relative to R0. The Anna chip has
128K of `dLB' ram nominally located at 0xFFF00000, but it's mirrored
every 128K, so we can use the `last mirror' (except for the portion at
the top which is overridden by I/O space). In addition, the early
sample chip we're using has lots of memory errors in the dLB ram, so we
use a specially chosen location that has at least 20 bytes of contiguous
valid memory (xxxF0020 - xxxF003F). */
#define R0_RAM_ADDR 0xFFFF8020
/* Anna specific control registers. */
#define ANNA_ILBEN_ADDR 0xFFFFF7F2
#define ANNA_ILBEN (*(volatile u16 *)ANNA_ILBEN_ADDR)
/* I/O port P0-P3. */
/* Direct I/O. Bits 0-7 are pins Pn0-Pn7. */
#define ANNA_PORT_IO_ADDR(n) (0xFFFFF400 + (n) * 2)
#define ANNA_PORT_IO(n) (*(volatile u8 *)ANNA_PORT_IO_ADDR(n))
/* Port mode (for direct I/O, 0 = output, 1 = input). */
#define ANNA_PORT_PM_ADDR(n) (0xFFFFF410 + (n) * 2)
#define ANNA_PORT_PM(n) (*(volatile u8 *)ANNA_PORT_PM_ADDR(n))
/* Hardware-specific interrupt numbers (in the kernel IRQ namespace). */
#define IRQ_INTP(n) (n) /* Pnnn (pin) interrupts 0-15 */
#define IRQ_INTP_NUM 16
#define IRQ_INTOV(n) (0x10 + (n)) /* 0-2 */
#define IRQ_INTOV_NUM 2
#define IRQ_INTCCC(n) (0x12 + (n))
#define IRQ_INTCCC_NUM 4
#define IRQ_INTCMD(n) (0x16 + (n)) /* interval timer interrupts 0-5 */
#define IRQ_INTCMD_NUM 6
#define IRQ_INTDMA(n) (0x1C + (n)) /* DMA interrupts 0-3 */
#define IRQ_INTDMA_NUM 4
#define IRQ_INTDMXER 0x20
#define IRQ_INTSRE(n) (0x21 + (n)*3) /* UART 0-1 reception error */
#define IRQ_INTSRE_NUM 2
#define IRQ_INTSR(n) (0x22 + (n)*3) /* UART 0-1 reception completion */
#define IRQ_INTSR_NUM 2
#define IRQ_INTST(n) (0x23 + (n)*3) /* UART 0-1 transmission completion */
#define IRQ_INTST_NUM 2
#define NUM_CPU_IRQS 64
#ifndef __ASSEMBLY__
/* Initialize chip interrupts. */
extern void anna_init_irqs (void);
#endif
/* Anna UART details (basically the same as the V850E/MA1, but 2 channels). */
#define V850E_UART_NUM_CHANNELS 2
#define V850E_UART_BASE_FREQ (SYS_CLOCK_FREQ / 2)
#define V850E_UART_CHIP_NAME "V850E2/NA85E2A"
/* This is the UART channel that's actually connected on the board. */
#define V850E_UART_CONSOLE_CHANNEL 1
/* This is a function that gets called before configuring the UART. */
#define V850E_UART_PRE_CONFIGURE anna_uart_pre_configure
#ifndef __ASSEMBLY__
extern void anna_uart_pre_configure (unsigned chan,
unsigned cflags, unsigned baud);
#endif
/* This board supports RTS/CTS for the on-chip UART, but only for channel 1. */
/* CTS for UART channel 1 is pin P37 (bit 7 of port 3). */
#define V850E_UART_CTS(chan) ((chan) == 1 ? !(ANNA_PORT_IO(3) & 0x80) : 1)
/* RTS for UART channel 1 is pin P07 (bit 7 of port 0). */
#define V850E_UART_SET_RTS(chan, val) \
do { \
if (chan == 1) { \
unsigned old = ANNA_PORT_IO(0); \
if (val) \
ANNA_PORT_IO(0) = old & ~0x80; \
else \
ANNA_PORT_IO(0) = old | 0x80; \
} \
} while (0)
/* Timer C details. */
#define V850E_TIMER_C_BASE_ADDR 0xFFFFF600
/* Timer D details (the Anna actually has 5 of these; should change later). */
#define V850E_TIMER_D_BASE_ADDR 0xFFFFF540
#define V850E_TIMER_D_TMD_BASE_ADDR (V850E_TIMER_D_BASE_ADDR + 0x0)
#define V850E_TIMER_D_CMD_BASE_ADDR (V850E_TIMER_D_BASE_ADDR + 0x2)
#define V850E_TIMER_D_TMCD_BASE_ADDR (V850E_TIMER_D_BASE_ADDR + 0x4)
#define V850E_TIMER_D_BASE_FREQ SYS_CLOCK_FREQ
#define V850E_TIMER_D_TMCD_CS_MIN 1 /* min 2^1 divider */
#endif /* __V850_ANNA_H__ */
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