arch/mips/alchemy/common/clocks.c

   1 /*
   2  * BRIEF MODULE DESCRIPTION
   3  *      Simple Au1xx0 clocks routines.
   4  *
   5  * Copyright 2001, 2008 MontaVista Software Inc.
   6  * Author: MontaVista Software, Inc. <source@mvista.com>
   7  *
   8  *  This program is free software; you can redistribute  it and/or modify it
   9  *  under  the terms of  the GNU General  Public License as published by the
  10  *  Free Software Foundation;  either version 2 of the  License, or (at your
  11  *  option) any later version.
  12  *
  13  *  THIS  SOFTWARE  IS PROVIDED   ``AS  IS'' AND   ANY  EXPRESS OR IMPLIED
  14  *  WARRANTIES,   INCLUDING, BUT NOT  LIMITED  TO, THE IMPLIED WARRANTIES OF
  15  *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
  16  *  NO  EVENT  SHALL   THE AUTHOR  BE    LIABLE FOR ANY   DIRECT, INDIRECT,
  17  *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  *  NOT LIMITED   TO, PROCUREMENT OF  SUBSTITUTE GOODS  OR SERVICES; LOSS OF
  19  *  USE, DATA,  OR PROFITS; OR  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
  20  *  ANY THEORY OF LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT
  21  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  *
  24  *  You should have received a copy of the  GNU General Public License along
  25  *  with this program; if not, write  to the Free Software Foundation, Inc.,
  26  *  675 Mass Ave, Cambridge, MA 02139, USA.
  27  */
  28
  29 #include <linux/module.h>
  30 #include <linux/spinlock.h>
  31 #include <asm/time.h>
  32 #include <asm/mach-au1x00/au1000.h>
  33
  34 /*
  35  * I haven't found anyone that doesn't use a 12 MHz source clock,
  36  * but just in case.....
  37  */
  38 #define AU1000_SRC_CLK  12000000
  39
  40 static unsigned int au1x00_clock; /*  Hz */
  41 static unsigned long uart_baud_base;
  42
  43 /*
  44  * Set the au1000_clock
  45  */
  46 void set_au1x00_speed(unsigned int new_freq)
  47 {
  48         au1x00_clock = new_freq;
  49 }
  50
  51 unsigned int get_au1x00_speed(void)
  52 {
  53         return au1x00_clock;
  54 }
  55 EXPORT_SYMBOL(get_au1x00_speed);
  56
  57 /*
  58  * The UART baud base is not known at compile time ... if
  59  * we want to be able to use the same code on different
  60  * speed CPUs.
  61  */
  62 unsigned long get_au1x00_uart_baud_base(void)
  63 {
  64         return uart_baud_base;
  65 }
  66
  67 void set_au1x00_uart_baud_base(unsigned long new_baud_base)
  68 {
  69         uart_baud_base = new_baud_base;
  70 }
  71
  72 /*
  73  * We read the real processor speed from the PLL.  This is important
  74  * because it is more accurate than computing it from the 32 KHz
  75  * counter, if it exists.  If we don't have an accurate processor
  76  * speed, all of the peripherals that derive their clocks based on
  77  * this advertised speed will introduce error and sometimes not work
  78  * properly.  This function is further convoluted to still allow configurations
  79  * to do that in case they have really, really old silicon with a
  80  * write-only PLL register.                     -- Dan
  81  */
  82 unsigned long au1xxx_calc_clock(void)
  83 {
  84         unsigned long cpu_speed;
  85
  86         /*
  87          * On early Au1000, sys_cpupll was write-only. Since these
  88          * silicon versions of Au1000 are not sold by AMD, we don't bend
  89          * over backwards trying to determine the frequency.
  90          */
  91         if (au1xxx_cpu_has_pll_wo())
  92                 cpu_speed = 396000000;
  93         else
  94                 cpu_speed = (au_readl(SYS_CPUPLL) & 0x0000003f) * AU1000_SRC_CLK;
  95
  96         /* On Alchemy CPU:counter ratio is 1:1 */
  97         mips_hpt_frequency = cpu_speed;
  98         /* Equation: Baudrate = CPU / (SD * 2 * CLKDIV * 16) */
  99         set_au1x00_uart_baud_base(cpu_speed / (2 * ((int)(au_readl(SYS_POWERCTRL)
 100                                                           & 0x03) + 2) * 16));
 101
 102         set_au1x00_speed(cpu_speed);
 103
 104         return cpu_speed;
 105 }