Hi Johan,
On Wed, May 09, 2018 at 11:44:18AM +0200, Johan Hovold wrote:
> Add support for controller runtime power management to serdev core. This
> is needed to allow slave drivers to manage the runtime PM state of the
> underlying serial controller when its driver, in turn, implements more
> aggressive runtime power management (e.g. using autosuspend).
>
> For some applications, for example, where loss off initial data after a
> remote-wakeup event is acceptable or where rx is not used at all,
> aggressive serial controller runtime PM may be used without further
> involvement of the slave driver. But when this is not the case, the
> slave driver must be able to indicate when incoming data is expected in
> order to avoid data loss.
>
> To facilitate the common case, where the serial controller power state
> is active whenever the port is open (which is the case with just about
> every serial driver), and where data loss is not acceptable and cannot
> even be prevented by explicit controller runtime power management, an
> RPM reference is taken in serdev open and put again at close. This
> reference can later be balanced by any serdev driver which wants and/or
> can handle aggressive controller runtime PM.
>
> Note that the .ignore_children flag is set for the serdev controller to
> allow the underlying hardware to idle when no I/O is expected, regardless
> of the slave device RPM state.
>
> Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
> ---
Looks good to me.
Reviewed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
-- Sebastian
> drivers/tty/serdev/core.c | 33 ++++++++++++++++++++++++++++++---
> 1 file changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index df93b727e984..e5e84303faca 100644
> --- a/drivers/tty/serdev/core.c
> +++ b/drivers/tty/serdev/core.c
> @@ -13,6 +13,7 @@
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> +#include <linux/pm_runtime.h>
> #include <linux/serdev.h>
> #include <linux/slab.h>
>
> @@ -143,11 +144,28 @@ EXPORT_SYMBOL_GPL(serdev_device_remove);
> int serdev_device_open(struct serdev_device *serdev)
> {
> struct serdev_controller *ctrl = serdev->ctrl;
> + int ret;
>
> if (!ctrl || !ctrl->ops->open)
> return -EINVAL;
>
> - return ctrl->ops->open(ctrl);
> + ret = ctrl->ops->open(ctrl);
> + if (ret)
> + return ret;
> +
> + ret = pm_runtime_get_sync(&ctrl->dev);
> + if (ret < 0) {
> + pm_runtime_put_noidle(&ctrl->dev);
> + goto err_close;
> + }
> +
> + return 0;
> +
> +err_close:
> + if (ctrl->ops->close)
> + ctrl->ops->close(ctrl);
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(serdev_device_open);
>
> @@ -158,6 +176,8 @@ void serdev_device_close(struct serdev_device *serdev)
> if (!ctrl || !ctrl->ops->close)
> return;
>
> + pm_runtime_put(&ctrl->dev);
> +
> ctrl->ops->close(ctrl);
> }
> EXPORT_SYMBOL_GPL(serdev_device_close);
> @@ -416,6 +436,9 @@ struct serdev_controller *serdev_controller_alloc(struct device *parent,
>
> dev_set_name(&ctrl->dev, "serial%d", id);
>
> + pm_runtime_no_callbacks(&ctrl->dev);
> + pm_suspend_ignore_children(&ctrl->dev, true);
> +
> dev_dbg(&ctrl->dev, "allocated controller 0x%p id %d\n", ctrl, id);
> return ctrl;
>
> @@ -547,20 +570,23 @@ int serdev_controller_add(struct serdev_controller *ctrl)
> if (ret)
> return ret;
>
> + pm_runtime_enable(&ctrl->dev);
> +
> ret_of = of_serdev_register_devices(ctrl);
> ret_acpi = acpi_serdev_register_devices(ctrl);
> if (ret_of && ret_acpi) {
> dev_dbg(&ctrl->dev, "no devices registered: of:%d acpi:%d\n",
> ret_of, ret_acpi);
> ret = -ENODEV;
> - goto out_dev_del;
> + goto err_rpm_disable;
> }
>
> dev_dbg(&ctrl->dev, "serdev%d registered: dev:%p\n",
> ctrl->nr, &ctrl->dev);
> return 0;
>
> -out_dev_del:
> +err_rpm_disable:
> + pm_runtime_disable(&ctrl->dev);
> device_del(&ctrl->dev);
> return ret;
> };
> @@ -591,6 +617,7 @@ void serdev_controller_remove(struct serdev_controller *ctrl)
>
> dummy = device_for_each_child(&ctrl->dev, NULL,
> serdev_remove_device);
> + pm_runtime_disable(&ctrl->dev);
> device_del(&ctrl->dev);
> }
> EXPORT_SYMBOL_GPL(serdev_controller_remove);
> --
> 2.17.0
>
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