linux/arch/arm/mach-omap2/wd_timer.c

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/*
* OMAP2+ MPU WD_TIMER-specific code
*
* 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/kernel.h>
#include <linux/io.h>
#include <linux/err.h>
#include <plat/omap_hwmod.h>
#include "wd_timer.h"
/*
* In order to avoid any assumptions from bootloader regarding WDT
* settings, WDT module is reset during init. This enables the watchdog
* timer. Hence it is required to disable the watchdog after the WDT reset
* during init. Otherwise the system would reboot as per the default
* watchdog timer registers settings.
*/
#define OMAP_WDT_WPS 0x34
#define OMAP_WDT_SPR 0x48
int omap2_wd_timer_disable(struct omap_hwmod *oh)
{
void __iomem *base;
if (!oh) {
pr_err("%s: Could not look up wdtimer_hwmod\n", __func__);
return -EINVAL;
}
base = omap_hwmod_get_mpu_rt_va(oh);
if (!base) {
pr_err("%s: Could not get the base address for %s\n",
oh->name, __func__);
return -EINVAL;
}
/* sequence required to disable watchdog */
__raw_writel(0xAAAA, base + OMAP_WDT_SPR);
while (__raw_readl(base + OMAP_WDT_WPS) & 0x10)
cpu_relax();
__raw_writel(0x5555, base + OMAP_WDT_SPR);
while (__raw_readl(base + OMAP_WDT_WPS) & 0x10)
cpu_relax();
OMAP2+: wd_timer: disable on boot via hwmod postsetup mechanism The OMAP watchdog timer IP blocks require a specific set of register writes to occur before they will be disabled[1], even if the device clocks appear to be disabled in the CM_*CLKEN registers. In the MPU watchdog case, failure to execute this reset sequence will eventually cause the watchdog to reset the OMAP unexpectedly. Previously, the code to disable this watchdog was manually called from mach-omap2/devices.c during device initialization. This causes the watchdog to be unconditionally disabled for a portion of kernel initialization. This should be controllable by the board-*.c files, since some system integrators will want full watchdog coverage of kernel initialization. Also, the watchdog disable code was not connected to the hwmod shutdown code. This means that calling omap_hwmod_shutdown() will not, in fact, disable the watchdog, and the goal of omap_hwmod_shutdown() is to be able to shutdown any on-chip OMAP device. To resolve the latter problem, populate the pre_shutdown pointer in the watchdog timer hwmod classes with a function that executes the watchdog shutdown sequence. This allows the hwmod code to fully disable the watchdog. Then, to allow some board files to support watchdog coverage throughout kernel initialization, add common code to mach-omap2/io.c to cause the MPU watchdog to be disabled on boot unless a board file specifically requests it to remain enabled. Board files can do this by changing the watchdog timer hwmod's postsetup state between the omap2_init_common_infrastructure() and omap2_init_common_devices() function calls. 1. OMAP34xx Multimedia Device Silicon Revision 3.1.x Rev. ZH [SWPU222H], Section 16.4.3.6, "Start/Stop Sequence for WDTs (Using WDTi.WSPR Register)" Signed-off-by: Paul Walmsley <paul@pwsan.com> Cc: Benoît Cousson <b-cousson@ti.com> Cc: Kevin Hilman <khilman@deeprootsystems.com> Cc: Charulatha Varadarajan <charu@ti.com>
2010-12-21 22:39:15 +00:00
return 0;
}