[PATCH v2 10/10] arm: zynq: Add cpuidle support
Daniel Lezcano
daniel.lezcano at linaro.org
Wed Mar 27 06:07:16 EDT 2013
On 03/26/2013 06:43 PM, Michal Simek wrote:
> Add support for cpuidle.
>
> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
Hi Michal,
at the first glance, the driver won't enter in the self refresh state.
If I am right, by checking:
/sys/devices/system/cpu/cpu0/cpuidle/state1/usage, it should be always zero.
Also, I see there is self refresh but you save the cpu context, so it is
cpu shutdown no ?
In this case, 3 states would be needed, WFI, self-refresh, powerdown, no ?
The comments below applies for this driver based on linux-pm-next.
https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/
> ---
> v2: Fix file header
> ---
> arch/arm/mach-zynq/Makefile | 1 +
> arch/arm/mach-zynq/cpuidle.c | 133 ++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 134 insertions(+)
> create mode 100644 arch/arm/mach-zynq/cpuidle.c
>
> diff --git a/arch/arm/mach-zynq/Makefile b/arch/arm/mach-zynq/Makefile
> index 1b25d92..238b8f9 100644
> --- a/arch/arm/mach-zynq/Makefile
> +++ b/arch/arm/mach-zynq/Makefile
> @@ -7,4 +7,5 @@ obj-y := common.o slcr.o
> CFLAGS_REMOVE_hotplug.o =-march=armv6k
> CFLAGS_hotplug.o =-Wa,-march=armv7-a -mcpu=cortex-a9
> obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o
> +obj-$(CONFIG_CPU_IDLE) += cpuidle.o
> obj-$(CONFIG_SMP) += headsmp.o platsmp.o
> diff --git a/arch/arm/mach-zynq/cpuidle.c b/arch/arm/mach-zynq/cpuidle.c
> new file mode 100644
> index 0000000..4ed8855
> --- /dev/null
> +++ b/arch/arm/mach-zynq/cpuidle.c
> @@ -0,0 +1,133 @@
> +/*
> + * Copyright (C) 2012-2013 Xilinx
> + *
> + * CPU idle support for Xilinx
> + *
> + * based on arch/arm/mach-at91/cpuidle.c
> + *
> + * 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.
> + *
> + * The cpu idle uses wait-for-interrupt and RAM self refresh in order
> + * to implement two idle states -
> + * #1 wait-for-interrupt
> + * #2 wait-for-interrupt and RAM self refresh
> + *
> + * Note that this code is only intended as a prototype and is not tested
> + * well yet, or tuned for the Xilinx Cortex A9. Also note that for a
> + * tickless kernel, high res timers must not be turned on. The cpuidle
> + * framework must also be turned on in the kernel.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/cpuidle.h>
> +#include <linux/io.h>
> +#include <linux/export.h>
> +#include <linux/clockchips.h>
> +#include <linux/cpu_pm.h>
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <asm/proc-fns.h>
> +
> +#define XILINX_MAX_STATES 1
You defined XILINX_MAX_STATES as 1, it should be 2.
> +static DEFINE_PER_CPU(struct cpuidle_device, xilinx_cpuidle_device);
> +
> +/* Actual code that puts the SoC in different idle states */
> +static int xilinx_enter_idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> +{
> + struct timeval before, after;
> + int idle_time;
> +
> + local_irq_disable();
Remove this line, it is done by the caller.
> + do_gettimeofday(&before);
Remove this line, that will be taken into account by the driver's
en_core_tk_irqen flag.
> +
> + if (index == 0)
> + /* Wait for interrupt state */
> + cpu_do_idle();
Don't check the index, see in the driver initialization comment below
the defaul wfi state. You will have one state entering WFI and the
xilinx_enter_idle function entering with always index 1.
> + else if (index == 1) {
> + unsigned int cpu_id = smp_processor_id();
> +
> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu_id);
Remove this line, CPUIDLE_FLAG_TIMER_STOP will tell the cpuidle
framework to handle that.
> + /* Devices must be stopped here */
> + cpu_pm_enter();
> +
> + /* Add code for DDR self refresh start */
> +
> + cpu_do_idle();
> + /*cpu_suspend(foo, bar);*/
> +
> + /* Add code for DDR self refresh stop */
> +
> + cpu_pm_exit();
> +
> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu_id);
Remove this line, CPUIDLE_FLAG_TIMER_STOP will tell the cpuidle
framework to handle that.
> + }
> +
> + do_gettimeofday(&after);
> + local_irq_enable();
> + idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
> + (after.tv_usec - before.tv_usec);
> +
> + dev->last_residency = idle_time;
Remove these lines about time computation, that is handled by the caller.
> + return index;
> +}
> +
> +static struct cpuidle_driver xilinx_idle_driver = {
> + .name = "xilinx_idle",
> + .owner = THIS_MODULE,
> + .state_count = XILINX_MAX_STATES,
> + /* Wait for interrupt state */
> + .states[0] = {
> + .enter = xilinx_enter_idle,
> + .exit_latency = 1,
> + .target_residency = 10000,
> + .flags = CPUIDLE_FLAG_TIME_VALID,
> + .name = "WFI",
> + .desc = "Wait for interrupt",
> + },
> + /* Wait for interrupt and RAM self refresh state */
> + .states[1] = {
> + .enter = xilinx_enter_idle,
> + .exit_latency = 10,
> + .target_residency = 10000,
> + .flags = CPUIDLE_FLAG_TIME_VALID,
> + .name = "RAM_SR",
> + .desc = "WFI and RAM Self Refresh",
> + },
> +};
static struct cpuidle_driver xilinx_idle_driver = {
.name = "xilinx_idle",
.owner = THIS_MODULE,
.states = {
ARM_CPUIDLE_WFI_STATE,
{
.enter = xilinx_enter_idle,
.exit_latency = 10,
.target_residency = 10000,
.flags = CPUIDLE_FLAG_TIME_VALID,
CPUIDLE_FLAG_TIMER_STOP,
.name = "RAM_SR",
.desc = "WFI and RAM Self Refresh",
},
},
.safe_state_index = 0,
.state_count = XILINX_MAX_STATES,
};
> +/* Initialize CPU idle by registering the idle states */
> +static int xilinx_init_cpuidle(void)
> +{
> + unsigned int cpu;
> + struct cpuidle_device *device;
> + int ret;
> +
> + ret = cpuidle_register_driver(&xilinx_idle_driver);
> + if (ret) {
> + pr_err("Registering Xilinx CpuIdle Driver failed.\n");
> + return ret;
> + }
> +
> + for_each_possible_cpu(cpu) {
> + device = &per_cpu(xilinx_cpuidle_device, cpu);
> + device->state_count = XILINX_MAX_STATES;
This is initialization is done from the cpuidle_register_device. As
drv->state_count == device->state_count.
> + device->cpu = cpu;
> + ret = cpuidle_register_device(device);
> + if (ret) {
> + pr_err("xilinx_init_cpuidle: Failed registering\n");
> + return ret;
> + }
> + }
> +
> + pr_info("Xilinx CpuIdle Driver started\n");
> + return 0;
> +}
> +device_initcall(xilinx_init_cpuidle);
>
--
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