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remarkable-linux/include/asm-v850/as85ep1.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/as85ep1.h -- AS85EP1 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_AS85EP1_H__
#define __V850_AS85EP1_H__
#include <asm/v850e.h>
#define CPU_MODEL "as85ep1"
#define CPU_MODEL_LONG "NEC V850E/AS85EP1"
#define PLATFORM "AS85EP1"
#define PLATFORM_LONG "NEC V850E/AS85EP1 evaluation board"
#define CPU_CLOCK_FREQ 96000000 /* 96MHz */
#define SYS_CLOCK_FREQ CPU_CLOCK_FREQ
/* 1MB of static RAM. */
#define SRAM_ADDR 0x00400000
#define SRAM_SIZE 0x00100000 /* 1MB */
/* About 58MB of DRAM. This can actually be at one of two positions,
determined by jump JP3; we have to use the first position because the
second is partially out of processor instruction addressing range
(though in the second position there's actually 64MB available). */
#define SDRAM_ADDR 0x00600000
#define SDRAM_SIZE 0x039F8000 /* approx 58MB */
/* 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 AS85EP1 chip
16K of internal RAM located slightly before I/O space. */
#define R0_RAM_ADDR 0xFFFF8000
/* AS85EP1 specific control registers. */
#define AS85EP1_CSC_ADDR(n) (0xFFFFF060 + (n) * 2)
#define AS85EP1_CSC(n) (*(volatile u16 *)AS85EP1_CSC_ADDR(n))
#define AS85EP1_BSC_ADDR 0xFFFFF066
#define AS85EP1_BSC (*(volatile u16 *)AS85EP1_BSC_ADDR)
#define AS85EP1_BCT_ADDR(n) (0xFFFFF480 + (n) * 2)
#define AS85EP1_BCT(n) (*(volatile u16 *)AS85EP1_BCT_ADDR(n))
#define AS85EP1_DWC_ADDR(n) (0xFFFFF484 + (n) * 2)
#define AS85EP1_DWC(n) (*(volatile u16 *)AS85EP1_DWC_ADDR(n))
#define AS85EP1_BCC_ADDR 0xFFFFF488
#define AS85EP1_BCC (*(volatile u16 *)AS85EP1_BCC_ADDR)
#define AS85EP1_ASC_ADDR 0xFFFFF48A
#define AS85EP1_ASC (*(volatile u16 *)AS85EP1_ASC_ADDR)
#define AS85EP1_BCP_ADDR 0xFFFFF48C
#define AS85EP1_BCP (*(volatile u16 *)AS85EP1_BCP_ADDR)
#define AS85EP1_LBS_ADDR 0xFFFFF48E
#define AS85EP1_LBS (*(volatile u16 *)AS85EP1_LBS_ADDR)
#define AS85EP1_BMC_ADDR 0xFFFFF498
#define AS85EP1_BMC (*(volatile u16 *)AS85EP1_BMC_ADDR)
#define AS85EP1_PRC_ADDR 0xFFFFF49A
#define AS85EP1_PRC (*(volatile u16 *)AS85EP1_PRC_ADDR)
#define AS85EP1_SCR_ADDR(n) (0xFFFFF4A0 + (n) * 4)
#define AS85EP1_SCR(n) (*(volatile u16 *)AS85EP1_SCR_ADDR(n))
#define AS85EP1_RFS_ADDR(n) (0xFFFFF4A2 + (n) * 4)
#define AS85EP1_RFS(n) (*(volatile u16 *)AS85EP1_RFS_ADDR(n))
#define AS85EP1_IRAMM_ADDR 0xFFFFF80A
#define AS85EP1_IRAMM (*(volatile u8 *)AS85EP1_IRAMM_ADDR)
/* I/O port P0-P13. */
/* Direct I/O. Bits 0-7 are pins Pn0-Pn7. */
#define AS85EP1_PORT_IO_ADDR(n) (0xFFFFF400 + (n) * 2)
#define AS85EP1_PORT_IO(n) (*(volatile u8 *)AS85EP1_PORT_IO_ADDR(n))
/* Port mode (for direct I/O, 0 = output, 1 = input). */
#define AS85EP1_PORT_PM_ADDR(n) (0xFFFFF420 + (n) * 2)
#define AS85EP1_PORT_PM(n) (*(volatile u8 *)AS85EP1_PORT_PM_ADDR(n))
/* Port mode control (0 = direct I/O mode, 1 = alternative I/O mode). */
#define AS85EP1_PORT_PMC_ADDR(n) (0xFFFFF440 + (n) * 2)
#define AS85EP1_PORT_PMC(n) (*(volatile u8 *)AS85EP1_PORT_PMC_ADDR(n))
/* Hardware-specific interrupt numbers (in the kernel IRQ namespace). */
#define IRQ_INTCCC(n) (0x0C + (n))
#define IRQ_INTCCC_NUM 8
#define IRQ_INTCMD(n) (0x14 + (n)) /* interval timer interrupts 0-5 */
#define IRQ_INTCMD_NUM 6
#define IRQ_INTSRE(n) (0x1E + (n)*3) /* UART 0-1 reception error */
#define IRQ_INTSRE_NUM 2
#define IRQ_INTSR(n) (0x1F + (n)*3) /* UART 0-1 reception completion */
#define IRQ_INTSR_NUM 2
#define IRQ_INTST(n) (0x20 + (n)*3) /* UART 0-1 transmission completion */
#define IRQ_INTST_NUM 2
#define NUM_CPU_IRQS 64
#ifndef __ASSEMBLY__
/* Initialize chip interrupts. */
extern void as85ep1_init_irqs (void);
#endif
/* AS85EP1 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 / 4)
#define V850E_UART_CHIP_NAME "V850E/NA85E"
/* This is a function that gets called before configuring the UART. */
#define V850E_UART_PRE_CONFIGURE as85ep1_uart_pre_configure
#ifndef __ASSEMBLY__
extern void as85ep1_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 P54 (bit 4 of port 5). */
#define V850E_UART_CTS(chan) ((chan) == 1 ? !(AS85EP1_PORT_IO(5) & 0x10) : 1)
/* RTS for UART channel 1 is pin P53 (bit 3 of port 5). */
#define V850E_UART_SET_RTS(chan, val) \
do { \
if (chan == 1) { \
unsigned old = AS85EP1_PORT_IO(5); \
if (val) \
AS85EP1_PORT_IO(5) = old & ~0x8; \
else \
AS85EP1_PORT_IO(5) = old | 0x8; \
} \
} while (0)
/* Timer C details. */
#define V850E_TIMER_C_BASE_ADDR 0xFFFFF600
/* Timer D details (the AS85EP1 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 2 /* min 2^2 divider */
#endif /* __V850_AS85EP1_H__ */
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