drivers/rtc/at91sam9_rtt.c

   1 /*
   2  * (C) Copyright 2010
   3  * Reinhard Meyer, reinhard.meyer@emk-elektronik.de
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 /*
  25  * Date & Time support for the internal Real-time Timer
  26  * of AT91SAM9260 and compatibles.
  27  * Compatible with the LinuX rtc driver workaround:
  28  * The RTT cannot be written to, but only reset.
  29  * The actual time is the sum of RTT and one of
  30  * the four GPBR registers.
  31  *
  32  * The at91sam9260 has 4 GPBR (0-3).
  33  * For their typical use see at91_gpbr.h !
  34  *
  35  * make sure u-boot and kernel use the same GPBR !
  36  */
  37
  38 #include <common.h>
  39 #include <command.h>
  40 #include <rtc.h>
  41 #include <asm/io.h>
  42 #include <asm/errno.h>
  43 #include <asm/arch/hardware.h>
  44 #include <asm/arch/at91_rtt.h>
  45 #include <asm/arch/at91_gpbr.h>
  46
  47 #if defined(CONFIG_CMD_DATE)
  48
  49 int rtc_get (struct rtc_time *tmp)
  50 {
  51         at91_rtt_t *rtt = (at91_rtt_t *) ATMEL_BASE_RTT;
  52         at91_gpbr_t *gpbr = (at91_gpbr_t *) ATMEL_BASE_GPBR;
  53         ulong tim;
  54         ulong tim2;
  55         ulong off;
  56
  57         do {
  58                 tim = readl(&rtt->vr);
  59                 tim2 = readl(&rtt->vr);
  60         } while (tim!=tim2);
  61         off = readl(&gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
  62         /* off==0 means time is invalid, but we ignore that */
  63         to_tm (tim+off, tmp);
  64         return 0;
  65 }
  66
  67 int rtc_set (struct rtc_time *tmp)
  68 {
  69         at91_rtt_t *rtt = (at91_rtt_t *) ATMEL_BASE_RTT;
  70         at91_gpbr_t *gpbr = (at91_gpbr_t *) ATMEL_BASE_GPBR;
  71         ulong tim;
  72
  73         tim = mktime (tmp->tm_year, tmp->tm_mon, tmp->tm_mday,
  74                       tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
  75
  76         /* clear alarm, set prescaler to 32768, clear counter */
  77         writel(32768+AT91_RTT_RTTRST, &rtt->mr);
  78         writel(~0, &rtt->ar);
  79         writel(tim, &gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
  80         /* wait for counter clear to happen, takes less than a 1/32768th second */
  81         while (readl(&rtt->vr) != 0)
  82                 ;
  83         return 0;
  84 }
  85
  86 void rtc_reset (void)
  87 {
  88         at91_rtt_t *rtt = (at91_rtt_t *) ATMEL_BASE_RTT;
  89         at91_gpbr_t *gpbr = (at91_gpbr_t *) ATMEL_BASE_GPBR;
  90
  91         /* clear alarm, set prescaler to 32768, clear counter */
  92         writel(32768+AT91_RTT_RTTRST, &rtt->mr);
  93         writel(~0, &rtt->ar);
  94         writel(0, &gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
  95         /* wait for counter clear to happen, takes less than a 1/32768th second */
  96         while (readl(&rtt->vr) != 0)
  97                 ;
  98 }
  99
 100 #endif