On Mon, Nov 9, 2020 at 4:00 PM Zhang Qilong <zhangqilo...@huawei.com> wrote:
>
> In many case, we need to check return value of pm_runtime_get_sync, but
> it brings a trouble to the usage counter processing. Many callers forget
> to decrease the usage counter when it failed. It has been discussed a
> lot[0][1]. So we add a function to deal with the usage counter for better
> coding.
>
> [0]https://lkml.org/lkml/2020/6/14/88
> [1]https://patchwork.ozlabs.org/project/linux-tegra/patch/20200520095148.10995-1-dinghao....@zju.edu.cn/
> Signed-off-by: Zhang Qilong <zhangqilo...@huawei.com>
> ---
> include/linux/pm_runtime.h | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> index 4b708f4e8eed..6549ce764400 100644
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -386,6 +386,36 @@ static inline int pm_runtime_get_sync(struct device *dev)
> return __pm_runtime_resume(dev, RPM_GET_PUT);
> }
>
> +/**
> + * pm_runtime_general_get - Bump up usage counter of a device and resume it.
> + * @dev: Target device.
> + *
> + * Increase runtime PM usage counter of @dev first, and carry out
> runtime-resume
> + * of it synchronously. If __pm_runtime_resume return negative value(device
> is in
> + * error state), we to need decrease the usage counter before it return. If
> + * __pm_runtime_resume return positive value, it means the runtime of device
> has
> + * already been in active state, and we let the new wrapper return zero
> instead.
> + *
> + * The possible return values of this function is zero or negative value.
> + * zero:
> + * - it means resume succeeed or runtime of device has already been
> active, the
> + * runtime PM usage counter of @dev remains incremented.
> + * negative:
> + * - it means failure and the runtime PM usage counter of @dev has been
> balanced.
The kerneldoc above is kind of noisy and it is hard to figure out what
the helper really does from it.
You could basically say something like "Resume @dev synchronously and
if that is successful, increment its runtime PM usage counter. Return
0 if the runtime PM usage counter of @dev has been incremented or a
negative error code otherwise."
> + */
> +static inline int pm_runtime_general_get(struct device *dev)
What about pm_runtime_resume_and_get()?
> +{
> + int ret = 0;
This extra initialization is not necessary.
You can initialize ret to the __pm_runtime_resume() return value right away.
> +
> + ret = __pm_runtime_resume(dev, RPM_GET_PUT);
> + if (ret < 0) {
> + pm_runtime_put_noidle(dev);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> /**
> * pm_runtime_put - Drop device usage counter and queue up "idle check" if 0.
> * @dev: Target device.
> --
