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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/arm/mach-s3c2410/time.c
downloadlinux-stericsson-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/* linux/arch/arm/mach-s3c2410/time.c
+ *
+ * Copyright (C) 2003-2005 Simtec Electronics
+ * Ben Dooks, <ben@simtec.co.uk>
+ *
+ * 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
+ */
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/err.h>
+
+#include <asm/system.h>
+#include <asm/leds.h>
+#include <asm/mach-types.h>
+
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <asm/arch/map.h>
+#include <asm/arch/regs-timer.h>
+#include <asm/arch/regs-irq.h>
+#include <asm/mach/time.h>
+#include <asm/hardware/clock.h>
+
+#include "clock.h"
+
+static unsigned long timer_startval;
+static unsigned long timer_usec_ticks;
+
+#define TIMER_USEC_SHIFT 16
+
+/* we use the shifted arithmetic to work out the ratio of timer ticks
+ * to usecs, as often the peripheral clock is not a nice even multiple
+ * of 1MHz.
+ *
+ * shift of 14 and 15 are too low for the 12MHz, 16 seems to be ok
+ * for the current HZ value of 200 without producing overflows.
+ *
+ * Original patch by Dimitry Andric, updated by Ben Dooks
+*/
+
+
+/* timer_mask_usec_ticks
+ *
+ * given a clock and divisor, make the value to pass into timer_ticks_to_usec
+ * to scale the ticks into usecs
+*/
+
+static inline unsigned long
+timer_mask_usec_ticks(unsigned long scaler, unsigned long pclk)
+{
+ unsigned long den = pclk / 1000;
+
+ return ((1000 << TIMER_USEC_SHIFT) * scaler + (den >> 1)) / den;
+}
+
+/* timer_ticks_to_usec
+ *
+ * convert timer ticks to usec.
+*/
+
+static inline unsigned long timer_ticks_to_usec(unsigned long ticks)
+{
+ unsigned long res;
+
+ res = ticks * timer_usec_ticks;
+ res += 1 << (TIMER_USEC_SHIFT - 4); /* round up slightly */
+
+ return res >> TIMER_USEC_SHIFT;
+}
+
+/***
+ * Returns microsecond since last clock interrupt. Note that interrupts
+ * will have been disabled by do_gettimeoffset()
+ * IRQs are disabled before entering here from do_gettimeofday()
+ */
+
+#define SRCPND_TIMER4 (1<<(IRQ_TIMER4 - IRQ_EINT0))
+
+static unsigned long s3c2410_gettimeoffset (void)
+{
+ unsigned long tdone;
+ unsigned long irqpend;
+ unsigned long tval;
+
+ /* work out how many ticks have gone since last timer interrupt */
+
+ tval = __raw_readl(S3C2410_TCNTO(4));
+ tdone = timer_startval - tval;
+
+ /* check to see if there is an interrupt pending */
+
+ irqpend = __raw_readl(S3C2410_SRCPND);
+ if (irqpend & SRCPND_TIMER4) {
+ /* re-read the timer, and try and fix up for the missed
+ * interrupt. Note, the interrupt may go off before the
+ * timer has re-loaded from wrapping.
+ */
+
+ tval = __raw_readl(S3C2410_TCNTO(4));
+ tdone = timer_startval - tval;
+
+ if (tval != 0)
+ tdone += timer_startval;
+ }
+
+ return timer_ticks_to_usec(tdone);
+}
+
+
+/*
+ * IRQ handler for the timer
+ */
+static irqreturn_t
+s3c2410_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+ write_seqlock(&xtime_lock);
+ timer_tick(regs);
+ write_sequnlock(&xtime_lock);
+ return IRQ_HANDLED;
+}
+
+static struct irqaction s3c2410_timer_irq = {
+ .name = "S3C2410 Timer Tick",
+ .flags = SA_INTERRUPT,
+ .handler = s3c2410_timer_interrupt
+};
+
+/*
+ * Set up timer interrupt, and return the current time in seconds.
+ *
+ * Currently we only use timer4, as it is the only timer which has no
+ * other function that can be exploited externally
+ */
+static void s3c2410_timer_setup (void)
+{
+ unsigned long tcon;
+ unsigned long tcnt;
+ unsigned long tcfg1;
+ unsigned long tcfg0;
+
+ tcnt = 0xffff; /* default value for tcnt */
+
+ /* read the current timer configuration bits */
+
+ tcon = __raw_readl(S3C2410_TCON);
+ tcfg1 = __raw_readl(S3C2410_TCFG1);
+ tcfg0 = __raw_readl(S3C2410_TCFG0);
+
+ /* configure the system for whichever machine is in use */
+
+ if (machine_is_bast() || machine_is_vr1000()) {
+ /* timer is at 12MHz, scaler is 1 */
+ timer_usec_ticks = timer_mask_usec_ticks(1, 12000000);
+ tcnt = 12000000 / HZ;
+
+ tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
+ tcfg1 |= S3C2410_TCFG1_MUX4_TCLK1;
+ } else {
+ unsigned long pclk;
+ struct clk *clk;
+
+ /* for the h1940 (and others), we use the pclk from the core
+ * to generate the timer values. since values around 50 to
+ * 70MHz are not values we can directly generate the timer
+ * value from, we need to pre-scale and divide before using it.
+ *
+ * for instance, using 50.7MHz and dividing by 6 gives 8.45MHz
+ * (8.45 ticks per usec)
+ */
+
+ /* this is used as default if no other timer can be found */
+
+ clk = clk_get(NULL, "timers");
+ if (IS_ERR(clk))
+ panic("failed to get clock for system timer");
+
+ clk_use(clk);
+ clk_enable(clk);
+
+ pclk = clk_get_rate(clk);
+
+ /* configure clock tick */
+
+ timer_usec_ticks = timer_mask_usec_ticks(6, pclk);
+
+ tcfg1 &= ~S3C2410_TCFG1_MUX4_MASK;
+ tcfg1 |= S3C2410_TCFG1_MUX4_DIV2;
+
+ tcfg0 &= ~S3C2410_TCFG_PRESCALER1_MASK;
+ tcfg0 |= ((6 - 1) / 2) << S3C2410_TCFG_PRESCALER1_SHIFT;
+
+ tcnt = (pclk / 6) / HZ;
+ }
+
+ /* timers reload after counting zero, so reduce the count by 1 */
+
+ tcnt--;
+
+ printk("timer tcon=%08lx, tcnt %04lx, tcfg %08lx,%08lx, usec %08lx\n",
+ tcon, tcnt, tcfg0, tcfg1, timer_usec_ticks);
+
+ /* check to see if timer is within 16bit range... */
+ if (tcnt > 0xffff) {
+ panic("setup_timer: HZ is too small, cannot configure timer!");
+ return;
+ }
+
+ __raw_writel(tcfg1, S3C2410_TCFG1);
+ __raw_writel(tcfg0, S3C2410_TCFG0);
+
+ timer_startval = tcnt;
+ __raw_writel(tcnt, S3C2410_TCNTB(4));
+
+ /* ensure timer is stopped... */
+
+ tcon &= ~(7<<20);
+ tcon |= S3C2410_TCON_T4RELOAD;
+ tcon |= S3C2410_TCON_T4MANUALUPD;
+
+ __raw_writel(tcon, S3C2410_TCON);
+ __raw_writel(tcnt, S3C2410_TCNTB(4));
+ __raw_writel(tcnt, S3C2410_TCMPB(4));
+
+ /* start the timer running */
+ tcon |= S3C2410_TCON_T4START;
+ tcon &= ~S3C2410_TCON_T4MANUALUPD;
+ __raw_writel(tcon, S3C2410_TCON);
+}
+
+static void __init s3c2410_timer_init (void)
+{
+ s3c2410_timer_setup();
+ setup_irq(IRQ_TIMER4, &s3c2410_timer_irq);
+}
+
+struct sys_timer s3c24xx_timer = {
+ .init = s3c2410_timer_init,
+ .offset = s3c2410_gettimeoffset,
+ .resume = s3c2410_timer_setup
+};