arch/arm/mach-at91/sysirq_mask.c

   1 /*
   2  * sysirq_mask.c - System-interrupt masking
   3  *
   4  * Copyright (C) 2013 Johan Hovold <jhovold@gmail.com>
   5  *
   6  * Functions to disable system interrupts from backup-powered peripherals.
   7  *
   8  * The RTC and RTT-peripherals are generally powered by backup power (VDDBU)
   9  * and are not reset on wake-up, user, watchdog or software reset. This means
  10  * that their interrupts may be enabled during early boot (e.g. after a user
  11  * reset).
  12  *
  13  * As the RTC and RTT share the system-interrupt line with the PIT, an
  14  * interrupt occurring before a handler has been installed would lead to the
  15  * system interrupt being disabled and prevent the system from booting.
  16  *
  17  * This program is free software; you can redistribute it and/or modify
  18  * it under the terms of the GNU General Public License as published by
  19  * the Free Software Foundation; either version 2 of the License, or
  20  * (at your option) any later version.
  21  */
  22
  23 #include <linux/io.h>
  24 #include <mach/at91_rtt.h>
  25
  26 #include "generic.h"
  27
  28 #define AT91_RTC_IDR            0x24    /* Interrupt Disable Register */
  29 #define AT91_RTC_IMR            0x28    /* Interrupt Mask Register */
  30 #define AT91_RTC_IRQ_MASK       0x1f    /* Available IRQs mask */
  31
  32 void __init at91_sysirq_mask_rtc(u32 rtc_base)
  33 {
  34         void __iomem *base;
  35
  36         base = ioremap(rtc_base, 64);
  37         if (!base)
  38                 return;
  39
  40         /*
  41          * sam9x5 SoCs have the following errata:
  42          * "RTC: Interrupt Mask Register cannot be used
  43          *  Interrupt Mask Register read always returns 0."
  44          *
  45          * Hence we're not relying on IMR values to disable
  46          * interrupts.
  47          */
  48         writel_relaxed(AT91_RTC_IRQ_MASK, base + AT91_RTC_IDR);
  49         (void)readl_relaxed(base + AT91_RTC_IMR);       /* flush */
  50
  51         iounmap(base);
  52 }
  53
  54 void __init at91_sysirq_mask_rtt(u32 rtt_base)
  55 {
  56         void __iomem *base;
  57         void __iomem *reg;
  58         u32 mode;
  59
  60         base = ioremap(rtt_base, 16);
  61         if (!base)
  62                 return;
  63
  64         reg = base + AT91_RTT_MR;
  65
  66         mode = readl_relaxed(reg);
  67         if (mode & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN)) {
  68                 pr_info("AT91: Disabling rtt irq\n");
  69                 mode &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
  70                 writel_relaxed(mode, reg);
  71                 (void)readl_relaxed(reg);                       /* flush */
  72         }
  73
  74         iounmap(base);
  75 }