On Mon, Nov 9, 2020 at 9:05 AM 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 | 32 ++++++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> index 4b708f4e8eed..2b0af5b1dffd 100644
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -386,6 +386,38 @@ static inline int pm_runtime_get_sync(struct device *dev)
> return __pm_runtime_resume(dev, RPM_GET_PUT);
> }
>
> +/**
> + * gene_pm_runtime_get_sync - Bump up usage counter of a device and resume
> it.
> + * @dev: Target device.
The force argument is not documented.
> + *
> + * 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) or return positive value(the runtime of device is already
> active)
> + * with force is true, it need decrease the usage counter of the device when
> + * return.
> + *
> + * The possible return values of this function is zero or negative value.
> + * zero:
> + * - it means success and the status will store the resume operation
> status
> + * if needed, the runtime PM usage counter of @dev remains incremented.
> + * negative:
> + * - it means failure and the runtime PM usage counter of @dev has been
> + * decreased.
> + * positive:
> + * - it means the runtime of the device is already active before that. If
> + * caller set force to true, we still need to decrease the usage
> counter.
Why is this needed?
> + */
> +static inline int gene_pm_runtime_get_sync(struct device *dev, bool force)
The name is not really a good one and note that pm_runtime_get() has
the same problem as _get_sync() (ie. the usage counter is incremented
regardless of the return value).
> +{
> + int ret = 0;
> +
> + ret = __pm_runtime_resume(dev, RPM_GET_PUT);
> + if (ret < 0 || (ret > 0 && force))
> + pm_runtime_put_noidle(dev);
> +
> + return ret;
> +}
> +
> /**
> * pm_runtime_put - Drop device usage counter and queue up "idle check" if 0.
> * @dev: Target device.
> --
Thanks!
