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authorwdenk <wdenk>2002-08-27 09:48:53 +0000
committerwdenk <wdenk>2002-08-27 09:48:53 +0000
commit4a9cbbe832e1c377d04cfb53e9679844595bc3cf (patch)
tree10a14a7f9764d6a3e2fe056bbc4538fc9004075a /cpu/mpc8xx/speed.c
parente887afc9da0fec9b7bbdf6b13b920ed30006edfc (diff)
Initial revision
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1 files changed, 187 insertions, 0 deletions
diff --git a/cpu/mpc8xx/speed.c 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);
+}
+
+/* ------------------------------------------------------------------------- */