linux/arch/arm/mach-at91/sysirq_mask.c
Johan Hovold 94c4c79f2f ARM: at91: fix hanged boot due to early rtt-interrupt
Make sure the RTT-interrupts are masked at boot by adding a new helper
function to be used at SOC-init.

This fixes hanged boot on all AT91 SOCs with an RTT, for example, if an
RTT-alarm goes off after a non-clean shutdown (e.g. when using RTC
wakeup).

The RTC and RTT-peripherals are powered by backup power (VDDBU) (on all
AT91 SOCs but RM9200) and are not reset on wake-up, user, watchdog or
software reset. This means that their interrupts may be enabled during
early boot if, for example, they where not disabled during a previous
shutdown (e.g. due to a buggy driver or a non-clean shutdown such as a
user reset). Furthermore, an RTC or RTT-alarm may also be active.

The RTC and RTT-interrupts use the shared system-interrupt line, which
is also used by the PIT, and if an interrupt occurs before a handler
(e.g. RTC-driver) has been installed this leads to the system interrupt
being disabled and prevents the system from booting.

Note that when boot hangs due to an early RTC or RTT-interrupt, the only
way to get the system to start again is to remove the backup power (e.g.
battery) or to disable the interrupt manually from the bootloader. In
particular, a user reset is not sufficient.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: stable@vger.kernel.org # 3.11.x
2013-11-15 12:13:33 +01:00

72 lines
1.9 KiB
C

/*
* sysirq_mask.c - System-interrupt masking
*
* Copyright (C) 2013 Johan Hovold <jhovold@gmail.com>
*
* Functions to disable system interrupts from backup-powered peripherals.
*
* The RTC and RTT-peripherals are generally powered by backup power (VDDBU)
* and are not reset on wake-up, user, watchdog or software reset. This means
* that their interrupts may be enabled during early boot (e.g. after a user
* reset).
*
* As the RTC and RTT share the system-interrupt line with the PIT, an
* interrupt occurring before a handler has been installed would lead to the
* system interrupt being disabled and prevent the system from booting.
*
* 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 <linux/io.h>
#include <mach/at91_rtt.h>
#include "generic.h"
#define AT91_RTC_IDR 0x24 /* Interrupt Disable Register */
#define AT91_RTC_IMR 0x28 /* Interrupt Mask Register */
void __init at91_sysirq_mask_rtc(u32 rtc_base)
{
void __iomem *base;
u32 mask;
base = ioremap(rtc_base, 64);
if (!base)
return;
mask = readl_relaxed(base + AT91_RTC_IMR);
if (mask) {
pr_info("AT91: Disabling rtc irq\n");
writel_relaxed(mask, base + AT91_RTC_IDR);
(void)readl_relaxed(base + AT91_RTC_IMR); /* flush */
}
iounmap(base);
}
void __init at91_sysirq_mask_rtt(u32 rtt_base)
{
void __iomem *base;
void __iomem *reg;
u32 mode;
base = ioremap(rtt_base, 16);
if (!base)
return;
reg = base + AT91_RTT_MR;
mode = readl_relaxed(reg);
if (mode & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN)) {
pr_info("AT91: Disabling rtt irq\n");
mode &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
writel_relaxed(mode, reg);
(void)readl_relaxed(reg); /* flush */
}
iounmap(base);
}