Initial revision

1 files changed, 187 insertions, 0 deletions

diff --git a/cpu/mpc8xx/speed.c b/cpu/mpc8xx/speed.c
new file mode 100644
index 0000000000..ef32371aba
--- /dev/null
+++ b/cpu/mpc8xx/speed.c
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+/*
+ * (C) Copyright 2000-2002
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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 <common.h>
+#include <mpc8xx.h>
+#include <asm/processor.h>
+
+#define PITC_SHIFT 16
+#define PITR_SHIFT 16
+/* pitc values to time for 58/8192 seconds (about 70.8 milliseconds) */
+#define SPEED_PIT_COUNTS 58
+#define SPEED_PITC	 ((SPEED_PIT_COUNTS - 1) << PITC_SHIFT)
+#define SPEED_PITC_INIT	 ((SPEED_PIT_COUNTS + 1) << PITC_SHIFT)
+
+#if !defined(CONFIG_8xx_GCLK_FREQ)
+/* Access functions for the Machine State Register */
+static __inline__ unsigned long get_msr(void)
+{
+	unsigned long msr;
+
+	asm volatile("mfmsr %0" : "=r" (msr) :);
+	return msr;
+}
+
+static __inline__ void set_msr(unsigned long msr)
+{
+	asm volatile("mtmsr %0" : : "r" (msr));
+}
+#endif
+
+/* ------------------------------------------------------------------------- */
+
+/*
+ * Measure CPU clock speed (core clock GCLK1, GCLK2),
+ * also determine bus clock speed (checking bus divider factor)
+ *
+ * (Approx. GCLK frequency in Hz)
+ *
+ * Initializes timer 2 and PIT, but disables them before return.
+ * [Use timer 2, because MPC823 CPUs mask 0.x do not have timers 3 and 4]
+ *
+ * When measuring the CPU clock against the PIT, we count cpu clocks
+ * for 58/8192 seconds with a prescale divide by 177 for the cpu clock.
+ * These strange values for the timing interval and prescaling are used
+ * because the formula for the CPU clock is:
+ *
+ *   CPU clock = count * (177 * (8192 / 58))
+ *
+ *             = count * 24999.7241
+ *
+ *   which is very close to
+ *
+ *             = count * 25000
+ *
+ * Since the count gives the CPU clock divided by 25000, we can get
+ * the CPU clock rounded to the nearest 0.1 MHz by
+ *
+ *   CPU clock = ((count + 2) / 4) * 100000;
+ *
+ * The rounding is important since the measurement is sometimes going
+ * to be high or low by 0.025 MHz, depending on exactly how the clocks
+ * and counters interact. By rounding we get the exact answer for any
+ * CPU clock that is an even multiple of 0.1 MHz.
+ */
+
+int get_clocks (void)
+{
+	DECLARE_GLOBAL_DATA_PTR;
+
+	volatile immap_t *immr = (immap_t *) CFG_IMMR;
+#ifndef	CONFIG_8xx_GCLK_FREQ
+	volatile cpmtimer8xx_t *timerp = &immr->im_cpmtimer;
+	ulong timer2_val;
+	ulong msr_val;
+
+	/* Reset + Stop Timer 2, no cascading
+	 */
+	timerp->cpmt_tgcr &= ~(TGCR_CAS2 | TGCR_RST2);
+
+	/* Keep stopped, halt in debug mode
+	 */
+	timerp->cpmt_tgcr |= (TGCR_FRZ2 | TGCR_STP2);
+
+	/* Timer 2 setup:
+	 * Output ref. interrupt disable, int. clock
+	 * Prescale by 177. Note that prescaler divides by value + 1
+	 * so we must subtract 1 here.
+	 */
+	timerp->cpmt_tmr2 = ((177 - 1) << TMR_PS_SHIFT) | TMR_ICLK_IN_GEN;
+
+	timerp->cpmt_tcn2 = 0;		/* reset state      */
+	timerp->cpmt_tgcr |= TGCR_RST2;	/* enable timer 2   */
+
+	/*
+	 * PIT setup:
+	 *
+         * We want to time for SPEED_PITC_COUNTS counts (of 8192 Hz),
+         * so the count value would be SPEED_PITC_COUNTS - 1.
+         * But there would be an uncertainty in the start time of 1/4
+         * count since when we enable the PIT the count is not
+         * synchronized to the 32768 Hz oscillator. The trick here is
+         * to start the count higher and wait until the PIT count
+         * changes to the required value before starting timer 2.
+	 *
+         * One count high should be enough, but occasionally the start
+         * is off by 1 or 2 counts of 32768 Hz. With the start value
+         * set two counts high it seems very reliable.
+         */
+
+	immr->im_sitk.sitk_pitck = KAPWR_KEY;	/* PIT initialization */
+	immr->im_sit.sit_pitc = SPEED_PITC_INIT;
+
+	immr->im_sitk.sitk_piscrk = KAPWR_KEY;
+	immr->im_sit.sit_piscr = CFG_PISCR;
+
+	/*
+	 * Start measurement - disable interrupts, just in case
+	 */
+	msr_val = get_msr ();
+	set_msr (msr_val & ~MSR_EE);
+
+	immr->im_sit.sit_piscr |= PISCR_PTE;
+
+	/* spin until get exact count when we want to start */
+	while (immr->im_sit.sit_pitr > SPEED_PITC);
+
+	timerp->cpmt_tgcr &= ~TGCR_STP2;	/* Start Timer 2    */
+	while ((immr->im_sit.sit_piscr & PISCR_PS) == 0);
+	timerp->cpmt_tgcr |= TGCR_STP2;		/* Stop  Timer 2    */
+
+	/* re-enable external interrupts if they were on */
+	set_msr (msr_val);
+
+	/* Disable timer and PIT
+	 */
+	timer2_val = timerp->cpmt_tcn2;		/* save before reset timer */
+
+	timerp->cpmt_tgcr &= ~(TGCR_RST2 | TGCR_FRZ2 | TGCR_STP2);
+	immr->im_sit.sit_piscr &= ~PISCR_PTE;
+
+	gd->cpu_clk = ((timer2_val + 2) / 4) * 100000L;	/* convert to Hz    */
+
+#else /* CONFIG_8xx_GCLK_FREQ */
+
+	/*
+         * If for some reason measuring the gclk frequency won't
+         * work, we return the hardwired value.
+         * (For example, the cogent CMA286-60 CPU module has no
+         * separate oscillator for PITRTCLK)
+	 */
+
+	gd->cpu_clk = CONFIG_8xx_GCLK_FREQ;
+
+#endif /* CONFIG_8xx_GCLK_FREQ */
+
+	if ((immr->im_clkrst.car_sccr & SCCR_EBDF11) == 0) {
+		/* No Bus Divider active */
+		gd->bus_clk = gd->cpu_clk;
+	} else {
+		/* The MPC8xx has only one BDF: half clock speed */
+		gd->bus_clk = gd->cpu_clk / 2;
+	}
+
+	return (0);
+}
+
+/* ------------------------------------------------------------------------- */