[PATCH V2 15/16] serial: 8250_bcm2835aux: add PM suspend/resume support

[Ulf Hansson]

On Sun, 28 Jul 2024 at 15:07, Stefan Wahren <wahrenst at gmx.net> wrote:
>
> This adds suspend/resume support for the 8250_bcm2835aux
> driver to provide power management support on attached
> devices.
>
> Signed-off-by: Stefan Wahren <wahrenst at gmx.net>
> ---
>  drivers/tty/serial/8250/8250_bcm2835aux.c | 37 +++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
> index 121a5ce86050..36e2bb34d82b 100644
> --- a/drivers/tty/serial/8250/8250_bcm2835aux.c
> +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
> @@ -13,6 +13,7 @@
>   */
>
>  #include <linux/clk.h>
> +#include <linux/console.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> @@ -213,11 +214,47 @@ static const struct acpi_device_id bcm2835aux_serial_acpi_match[] = {
>  };
>  MODULE_DEVICE_TABLE(acpi, bcm2835aux_serial_acpi_match);
>
> +static int bcm2835aux_suspend(struct device *dev)
> +{
> +       struct bcm2835aux_data *data = dev_get_drvdata(dev);
> +       struct uart_8250_port *up = serial8250_get_port(data->line);
> +
> +       serial8250_suspend_port(data->line);
> +
> +       if (device_may_wakeup(dev))
> +               return 0;
> +
> +       if (uart_console(&up->port) && !console_suspend_enabled)
> +               return 0;
> +
> +       clk_disable_unprepare(data->clk);
> +       return 0;
> +}
> +
> +static int bcm2835aux_resume(struct device *dev)
> +{
> +       struct bcm2835aux_data *data = dev_get_drvdata(dev);
> +       int ret;
> +
> +       ret = clk_prepare_enable(data->clk);

Doesn't this create clk prepare/enable - unprepare/disable imbalance
problem when the uart is configured for system wakeup?

> +       if (ret)
> +               return ret;
> +
> +       serial8250_resume_port(data->line);
> +
> +       return 0;
> +}
> +
> +static const struct dev_pm_ops bcm2835aux_dev_pm_ops = {
> +       SYSTEM_SLEEP_PM_OPS(bcm2835aux_suspend, bcm2835aux_resume)
> +};
> +
>  static struct platform_driver bcm2835aux_serial_driver = {
>         .driver = {
>                 .name = "bcm2835-aux-uart",
>                 .of_match_table = bcm2835aux_serial_match,
>                 .acpi_match_table = bcm2835aux_serial_acpi_match,
> +               .pm = pm_ptr(&bcm2835aux_dev_pm_ops),
>         },
>         .probe  = bcm2835aux_serial_probe,
>         .remove_new = bcm2835aux_serial_remove,
> --
> 2.34.1
>

Kind regards
Uffe