diff options
Diffstat (limited to 'arch/arm/cpu/arm920t/at91/clock.c')
| -rw-r--r-- | arch/arm/cpu/arm920t/at91/clock.c | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/arch/arm/cpu/arm920t/at91/clock.c b/arch/arm/cpu/arm920t/at91/clock.c new file mode 100644 index 0000000..696200d --- /dev/null +++ b/arch/arm/cpu/arm920t/at91/clock.c @@ -0,0 +1,160 @@ +/* + * [origin: Linux kernel linux/arch/arm/mach-at91/clock.c] + * + * Copyright (C) 2011 Andreas Bießmann + * Copyright (C) 2005 David Brownell + * Copyright (C) 2005 Ivan Kokshaysky + * Copyright (C) 2009 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com> + * + * 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. + */ +#include <common.h> +#include <asm/io.h> +#include <asm/arch/hardware.h> +#include <asm/arch/at91_pmc.h> +#include <asm/arch/clk.h> + +#if !defined(CONFIG_AT91FAMILY) +# error You need to define CONFIG_AT91FAMILY in your board config! +#endif + +DECLARE_GLOBAL_DATA_PTR; + +static unsigned long at91_css_to_rate(unsigned long css) +{ + switch (css) { + case AT91_PMC_MCKR_CSS_SLOW: + return CONFIG_SYS_AT91_SLOW_CLOCK; + case AT91_PMC_MCKR_CSS_MAIN: + return gd->arch.main_clk_rate_hz; + case AT91_PMC_MCKR_CSS_PLLA: + return gd->arch.plla_rate_hz; + case AT91_PMC_MCKR_CSS_PLLB: + return gd->arch.pllb_rate_hz; + } + + return 0; +} + +#ifdef CONFIG_USB_ATMEL +static unsigned at91_pll_calc(unsigned main_freq, unsigned out_freq) +{ + unsigned i, div = 0, mul = 0, diff = 1 << 30; + unsigned ret = (out_freq > 155000000) ? 0xbe00 : 0x3e00; + + /* PLL output max 240 MHz (or 180 MHz per errata) */ + if (out_freq > 240000000) + goto fail; + + for (i = 1; i < 256; i++) { + int diff1; + unsigned input, mul1; + + /* + * PLL input between 1MHz and 32MHz per spec, but lower + * frequences seem necessary in some cases so allow 100K. + * Warning: some newer products need 2MHz min. + */ + input = main_freq / i; + if (input < 100000) + continue; + if (input > 32000000) + continue; + + mul1 = out_freq / input; + if (mul1 > 2048) + continue; + if (mul1 < 2) + goto fail; + + diff1 = out_freq - input * mul1; + if (diff1 < 0) + diff1 = -diff1; + if (diff > diff1) { + diff = diff1; + div = i; + mul = mul1; + if (diff == 0) + break; + } + } + if (i == 256 && diff > (out_freq >> 5)) + goto fail; + return ret | ((mul - 1) << 16) | div; +fail: + return 0; +} +#endif + +static u32 at91_pll_rate(u32 freq, u32 reg) +{ + unsigned mul, div; + + div = reg & 0xff; + mul = (reg >> 16) & 0x7ff; + if (div && mul) { + freq /= div; + freq *= mul + 1; + } else + freq = 0; + + return freq; +} + +int at91_clock_init(unsigned long main_clock) +{ + unsigned freq, mckr; + at91_pmc_t *pmc = (at91_pmc_t *) ATMEL_BASE_PMC; +#ifndef CONFIG_SYS_AT91_MAIN_CLOCK + unsigned tmp; + /* + * When the bootloader initialized the main oscillator correctly, + * there's no problem using the cycle counter. But if it didn't, + * or when using oscillator bypass mode, we must be told the speed + * of the main clock. + */ + if (!main_clock) { + do { + tmp = readl(&pmc->mcfr); + } while (!(tmp & AT91_PMC_MCFR_MAINRDY)); + tmp &= AT91_PMC_MCFR_MAINF_MASK; + main_clock = tmp * (CONFIG_SYS_AT91_SLOW_CLOCK / 16); + } +#endif + gd->arch.main_clk_rate_hz = main_clock; + + /* report if PLLA is more than mildly overclocked */ + gd->arch.plla_rate_hz = at91_pll_rate(main_clock, readl(&pmc->pllar)); + +#ifdef CONFIG_USB_ATMEL + /* + * USB clock init: choose 48 MHz PLLB value, + * disable 48MHz clock during usb peripheral suspend. + * + * REVISIT: assumes MCK doesn't derive from PLLB! + */ + gd->arch.at91_pllb_usb_init = at91_pll_calc(main_clock, 48000000 * 2) | + AT91_PMC_PLLBR_USBDIV_2; + gd->arch.pllb_rate_hz = at91_pll_rate(main_clock, + gd->arch.at91_pllb_usb_init); +#endif + + /* + * MCK and CPU derive from one of those primary clocks. + * For now, assume this parentage won't change. + */ + mckr = readl(&pmc->mckr); + gd->arch.mck_rate_hz = at91_css_to_rate(mckr & AT91_PMC_MCKR_CSS_MASK); + freq = gd->arch.mck_rate_hz; + + freq /= (1 << ((mckr & AT91_PMC_MCKR_PRES_MASK) >> 2)); /* prescale */ + /* mdiv */ + gd->arch.mck_rate_hz = freq / + (1 + ((mckr & AT91_PMC_MCKR_MDIV_MASK) >> 8)); + gd->arch.cpu_clk_rate_hz = freq; + + return 0; +} |
