blob: 207e81275ff01277331eec126c736c397831a370 [file] [log] [blame]
* arch/arm/mach-lpc32xx/pm.c
* Original authors: Vitaly Wool, Dmitry Chigirev <>
* Modified by Kevin Wells <>
* 2005 (c) MontaVista Software, Inc. This file is licensed under
* the terms of the GNU General Public License version 2. This program
* is licensed "as is" without any warranty of any kind, whether express
* or implied.
* LPC32XX CPU and system power management
* The LPC32XX has three CPU modes for controlling system power: run,
* direct-run, and halt modes. When switching between halt and run modes,
* the CPU transistions through direct-run mode. For Linux, direct-run
* mode is not used in normal operation. Halt mode is used when the
* system is fully suspended.
* Run mode:
* The ARM CPU clock (HCLK_PLL), HCLK bus clock, and PCLK bus clocks are
* derived from the HCLK PLL. The HCLK and PCLK bus rates are divided from
* the HCLK_PLL rate. Linux runs in this mode.
* Direct-run mode:
* The ARM CPU clock, HCLK bus clock, and PCLK bus clocks are driven from
* SYSCLK. SYSCLK is usually around 13MHz, but may vary based on SYSCLK
* source or the frequency of the main oscillator. In this mode, the
* HCLK_PLL can be safely enabled, changed, or disabled.
* Halt mode:
* SYSCLK is gated off and the CPU and system clocks are halted.
* Peripherals based on the 32KHz oscillator clock (ie, RTC, touch,
* key scanner, etc.) still operate if enabled. In this state, an enabled
* system event (ie, GPIO state change, RTC match, key press, etc.) will
* wake the system up back into direct-run mode.
* DRAM refresh
* DRAM clocking and refresh are slightly different for systems with DDR
* DRAM or regular SDRAM devices. If SDRAM is used in the system, the
* SDRAM will still be accessible in direct-run mode. In DDR based systems,
* a transition to direct-run mode will stop all DDR accesses (no clocks).
* Because of this, the code to switch power modes and the code to enter
* and exit DRAM self-refresh modes must not be executed in DRAM. A small
* section of IRAM is used instead for this.
* Suspend is handled with the following logic:
* Backup a small area of IRAM used for the suspend code
* Copy suspend code to IRAM
* Transfer control to code in IRAM
* Places DRAMs in self-refresh mode
* Enter direct-run mode
* Save state of HCLK_PLL PLL
* Disable HCLK_PLL PLL
* Enter halt mode - CPU and buses will stop
* System enters direct-run mode when an enabled event occurs
* HCLK PLL state is restored
* Run mode is entered
* DRAMS are placed back into normal mode
* Code execution returns from IRAM
* IRAM code are used for suspend is restored
* Suspend mode is exited
#include <linux/suspend.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <mach/hardware.h>
#include <mach/platform.h>
#include "common.h"
#include "clock.h"
* Both STANDBY and MEM suspend states are handled the same with no
* loss of CPU or memory state
static int lpc32xx_pm_enter(suspend_state_t state)
int (*lpc32xx_suspend_ptr) (void);
void *iram_swap_area;
/* Allocate some space for temporary IRAM storage */
iram_swap_area = kmalloc(lpc32xx_sys_suspend_sz, GFP_KERNEL);
if (!iram_swap_area) {
"PM Suspend: cannot allocate memory to save portion "
"of SRAM\n");
return -ENOMEM;
/* Backup a small area of IRAM used for the suspend code */
memcpy(iram_swap_area, (void *) TEMP_IRAM_AREA,
* Copy code to suspend system into IRAM. The suspend code
* needs to run from IRAM as DRAM may no longer be available
* when the PLL is stopped.
memcpy((void *) TEMP_IRAM_AREA, &lpc32xx_sys_suspend,
flush_icache_range((unsigned long)TEMP_IRAM_AREA,
(unsigned long)(TEMP_IRAM_AREA) + lpc32xx_sys_suspend_sz);
/* Transfer to suspend code in IRAM */
lpc32xx_suspend_ptr = (void *) TEMP_IRAM_AREA;
(void) lpc32xx_suspend_ptr();
/* Restore original IRAM contents */
memcpy((void *) TEMP_IRAM_AREA, iram_swap_area,
return 0;
static const struct platform_suspend_ops lpc32xx_pm_ops = {
.valid = suspend_valid_only_mem,
.enter = lpc32xx_pm_enter,
#define EMC_DYN_MEM_CTRL_OFS 0x20
#define EMC_SRMMC (1 << 3)
static int __init lpc32xx_pm_init(void)
* Setup SDRAM self-refresh clock to automatically disable o
* start of self-refresh. This only needs to be done once.
__raw_writel(__raw_readl(EMC_CTRL_REG) | EMC_SRMMC, EMC_CTRL_REG);
return 0;