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e978aa7d7d
Cpuidle governor only suggests the state to enter using the governor->select() interface, but allows the low level driver to override the recommended state. The actual entered state may be different because of software or hardware demotion. Software demotion is done by the back-end cpuidle driver and can be accounted correctly. Current cpuidle code uses last_state field to capture the actual state entered and based on that updates the statistics for the state entered. Ideally the driver enter routine should update the counters, and it should return the state actually entered rather than the time spent there. The generic cpuidle code should simply handle where the counters live in the sysfs namespace, not updating the counters. Reference: https://lkml.org/lkml/2011/3/25/52 Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com> Signed-off-by: Trinabh Gupta <g.trinabh@gmail.com> Tested-by: Jean Pihet <j-pihet@ti.com> Reviewed-by: Kevin Hilman <khilman@ti.com> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Kevin Hilman <khilman@ti.com> Signed-off-by: Len Brown <len.brown@intel.com>
97 lines
2.6 KiB
C
97 lines
2.6 KiB
C
/*
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* based on arch/arm/mach-kirkwood/cpuidle.c
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*
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* CPU idle support for AT91 SoC
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*
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* This file is licensed under the terms of the GNU General Public
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* License version 2. This program is licensed "as is" without any
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* warranty of any kind, whether express or implied.
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*
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* The cpu idle uses wait-for-interrupt and RAM self refresh in order
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* to implement two idle states -
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* #1 wait-for-interrupt
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* #2 wait-for-interrupt and RAM self refresh
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/platform_device.h>
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#include <linux/cpuidle.h>
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#include <asm/proc-fns.h>
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#include <linux/io.h>
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#include "pm.h"
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#define AT91_MAX_STATES 2
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static DEFINE_PER_CPU(struct cpuidle_device, at91_cpuidle_device);
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static struct cpuidle_driver at91_idle_driver = {
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.name = "at91_idle",
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.owner = THIS_MODULE,
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};
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/* Actual code that puts the SoC in different idle states */
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static int at91_enter_idle(struct cpuidle_device *dev,
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int index)
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{
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struct timeval before, after;
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int idle_time;
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u32 saved_lpr;
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local_irq_disable();
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do_gettimeofday(&before);
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if (index == 0)
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/* Wait for interrupt state */
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cpu_do_idle();
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else if (index == 1) {
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asm("b 1f; .align 5; 1:");
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asm("mcr p15, 0, r0, c7, c10, 4"); /* drain write buffer */
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saved_lpr = sdram_selfrefresh_enable();
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cpu_do_idle();
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sdram_selfrefresh_disable(saved_lpr);
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}
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do_gettimeofday(&after);
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local_irq_enable();
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idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
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(after.tv_usec - before.tv_usec);
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dev->last_residency = idle_time;
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return index;
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}
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/* Initialize CPU idle by registering the idle states */
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static int at91_init_cpuidle(void)
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{
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struct cpuidle_device *device;
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cpuidle_register_driver(&at91_idle_driver);
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device = &per_cpu(at91_cpuidle_device, smp_processor_id());
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device->state_count = AT91_MAX_STATES;
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/* Wait for interrupt state */
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device->states[0].enter = at91_enter_idle;
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device->states[0].exit_latency = 1;
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device->states[0].target_residency = 10000;
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device->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
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strcpy(device->states[0].name, "WFI");
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strcpy(device->states[0].desc, "Wait for interrupt");
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/* Wait for interrupt and RAM self refresh state */
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device->states[1].enter = at91_enter_idle;
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device->states[1].exit_latency = 10;
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device->states[1].target_residency = 10000;
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device->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
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strcpy(device->states[1].name, "RAM_SR");
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strcpy(device->states[1].desc, "WFI and RAM Self Refresh");
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if (cpuidle_register_device(device)) {
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printk(KERN_ERR "at91_init_cpuidle: Failed registering\n");
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return -EIO;
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}
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return 0;
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}
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device_initcall(at91_init_cpuidle);
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