lkml.org 
[lkml]   [2020]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] counter: stm32-timer-cnt: add power management support
On Wed, 5 Feb 2020 11:47:58 +0100
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> Add suspend/resume PM sleep ops. When going to low power, enforce the
> counter isn't active.
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> ---
> drivers/counter/stm32-timer-cnt.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
> index 3eafcce..3b84503 100644
> --- a/drivers/counter/stm32-timer-cnt.c
> +++ b/drivers/counter/stm32-timer-cnt.c
> @@ -12,6 +12,7 @@
> #include <linux/iio/types.h>
> #include <linux/mfd/stm32-timers.h>
> #include <linux/module.h>
> +#include <linux/pinctrl/consumer.h>
> #include <linux/platform_device.h>
>
> #define TIM_CCMR_CCXS (BIT(8) | BIT(0))
> @@ -358,10 +359,33 @@ static int stm32_timer_cnt_probe(struct platform_device *pdev)
> priv->counter.num_signals = ARRAY_SIZE(stm32_signals);
> priv->counter.priv = priv;
>
> + platform_set_drvdata(pdev, priv);
> +
> /* Register Counter device */
> return devm_counter_register(dev, &priv->counter);
> }
>
> +static int __maybe_unused stm32_timer_cnt_suspend(struct device *dev)
> +{
> + struct stm32_timer_cnt *priv = dev_get_drvdata(dev);
> + u32 cr1;
> +
> + /* Check for active counter */
> + regmap_read(priv->regmap, TIM_CR1, &cr1);
> + if (cr1 & TIM_CR1_CEN)
> + return -EBUSY;

Runtime suspend is allowed to refuse to happen (and that is
explicitly documented)
Is that allowed for normal suspend? I didn't think it was.
This will stop a suspend, but it's doing it by signalling a failure.
I'm not sure for example that the system will resume everything that
was suspended before this call.

Normally you are in the tough luck category if a system decides
to suspend underneath you. There are ways to prevent it
from userspace (wakelocks etc).

> +
> + return pinctrl_pm_select_sleep_state(dev);
> +}
> +
> +static int __maybe_unused stm32_timer_cnt_resume(struct device *dev)
> +{
> + return pinctrl_pm_select_default_state(dev);
> +}
> +
> +static SIMPLE_DEV_PM_OPS(stm32_timer_cnt_pm_ops, stm32_timer_cnt_suspend,
> + stm32_timer_cnt_resume);
> +
> static const struct of_device_id stm32_timer_cnt_of_match[] = {
> { .compatible = "st,stm32-timer-counter", },
> {},
> @@ -373,6 +397,7 @@ static struct platform_driver stm32_timer_cnt_driver = {
> .driver = {
> .name = "stm32-timer-counter",
> .of_match_table = stm32_timer_cnt_of_match,
> + .pm = &stm32_timer_cnt_pm_ops,
> },
> };
> module_platform_driver(stm32_timer_cnt_driver);

\
 
 \ /
  Last update: 2020-02-08 16:37    [W:0.071 / U:3.440 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site