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    Subject[PATCH 6/7] tty: serial: samsung_tty: Support runtime PM
    Date
    This allows idle UART devices to be suspended using the standard
    runtime-PM framework. The logic is modeled after stm32-usart.

    Signed-off-by: Hector Martin <marcan@marcan.st>
    ---
    drivers/tty/serial/samsung_tty.c | 88 ++++++++++++++++++++------------
    1 file changed, 54 insertions(+), 34 deletions(-)

    diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
    index e2f49863e9c2..d68e3341adc6 100644
    --- a/drivers/tty/serial/samsung_tty.c
    +++ b/drivers/tty/serial/samsung_tty.c
    @@ -40,6 +40,7 @@
    #include <linux/clk.h>
    #include <linux/cpufreq.h>
    #include <linux/of.h>
    +#include <linux/pm_runtime.h>
    #include <asm/irq.h>

    /* UART name and device definitions */
    @@ -1381,31 +1382,49 @@ static void exynos_usi_init(struct uart_port *port)

    /* power power management control */

    -static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
    - unsigned int old)
    +static int __maybe_unused s3c24xx_serial_runtime_suspend(struct device *dev)
    {
    + struct uart_port *port = dev_get_drvdata(dev);
    struct s3c24xx_uart_port *ourport = to_ourport(port);
    int timeout = 10000;

    - ourport->pm_level = level;
    + while (--timeout && !s3c24xx_serial_txempty_nofifo(port))
    + udelay(100);

    - switch (level) {
    - case 3:
    - while (--timeout && !s3c24xx_serial_txempty_nofifo(port))
    - udelay(100);
    + if (!IS_ERR(ourport->baudclk))
    + clk_disable_unprepare(ourport->baudclk);

    - if (!IS_ERR(ourport->baudclk))
    - clk_disable_unprepare(ourport->baudclk);
    + clk_disable_unprepare(ourport->clk);
    + return 0;
    +};

    - clk_disable_unprepare(ourport->clk);
    - break;
    +static int __maybe_unused s3c24xx_serial_runtime_resume(struct device *dev)
    +{
    + struct uart_port *port = dev_get_drvdata(dev);
    + struct s3c24xx_uart_port *ourport = to_ourport(port);

    - case 0:
    - clk_prepare_enable(ourport->clk);
    + clk_prepare_enable(ourport->clk);

    - if (!IS_ERR(ourport->baudclk))
    - clk_prepare_enable(ourport->baudclk);
    + if (!IS_ERR(ourport->baudclk))
    + clk_prepare_enable(ourport->baudclk);
    + return 0;
    +};
    +
    +static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
    + unsigned int old)
    +{
    + struct s3c24xx_uart_port *ourport = to_ourport(port);
    +
    + ourport->pm_level = level;

    + switch (level) {
    + case UART_PM_STATE_OFF:
    + pm_runtime_mark_last_busy(port->dev);
    + pm_runtime_put_sync(port->dev);
    + break;
    +
    + case UART_PM_STATE_ON:
    + pm_runtime_get_sync(port->dev);
    exynos_usi_init(port);
    break;
    default:
    @@ -2282,18 +2301,15 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
    }
    }

    + pm_runtime_get_noresume(&pdev->dev);
    + pm_runtime_set_active(&pdev->dev);
    + pm_runtime_enable(&pdev->dev);
    +
    dev_dbg(&pdev->dev, "%s: adding port\n", __func__);
    uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
    platform_set_drvdata(pdev, &ourport->port);

    - /*
    - * Deactivate the clock enabled in s3c24xx_serial_init_port here,
    - * so that a potential re-enablement through the pm-callback overlaps
    - * and keeps the clock enabled in this case.
    - */
    - clk_disable_unprepare(ourport->clk);
    - if (!IS_ERR(ourport->baudclk))
    - clk_disable_unprepare(ourport->baudclk);
    + pm_runtime_put_sync(&pdev->dev);

    ret = s3c24xx_serial_cpufreq_register(ourport);
    if (ret < 0)
    @@ -2309,8 +2325,14 @@ static int s3c24xx_serial_remove(struct platform_device *dev)
    struct uart_port *port = s3c24xx_dev_to_port(&dev->dev);

    if (port) {
    + pm_runtime_get_sync(&dev->dev);
    +
    s3c24xx_serial_cpufreq_deregister(to_ourport(port));
    uart_remove_one_port(&s3c24xx_uart_drv, port);
    +
    + pm_runtime_disable(&dev->dev);
    + pm_runtime_set_suspended(&dev->dev);
    + pm_runtime_put_noidle(&dev->dev);
    }

    uart_unregister_driver(&s3c24xx_uart_drv);
    @@ -2319,8 +2341,8 @@ static int s3c24xx_serial_remove(struct platform_device *dev)
    }

    /* UART power management code */
    -#ifdef CONFIG_PM_SLEEP
    -static int s3c24xx_serial_suspend(struct device *dev)
    +
    +static int __maybe_unused s3c24xx_serial_suspend(struct device *dev)
    {
    struct uart_port *port = s3c24xx_dev_to_port(dev);

    @@ -2330,7 +2352,7 @@ static int s3c24xx_serial_suspend(struct device *dev)
    return 0;
    }

    -static int s3c24xx_serial_resume(struct device *dev)
    +static int __maybe_unused s3c24xx_serial_resume(struct device *dev)
    {
    struct uart_port *port = s3c24xx_dev_to_port(dev);
    struct s3c24xx_uart_port *ourport = to_ourport(port);
    @@ -2350,7 +2372,7 @@ static int s3c24xx_serial_resume(struct device *dev)
    return 0;
    }

    -static int s3c24xx_serial_resume_noirq(struct device *dev)
    +static int __maybe_unused s3c24xx_serial_resume_noirq(struct device *dev)
    {
    struct uart_port *port = s3c24xx_dev_to_port(dev);
    struct s3c24xx_uart_port *ourport = to_ourport(port);
    @@ -2420,16 +2442,14 @@ static int s3c24xx_serial_resume_noirq(struct device *dev)
    }

    static const struct dev_pm_ops s3c24xx_serial_pm_ops = {
    +#ifdef CONFIG_PM_SLEEP
    .suspend = s3c24xx_serial_suspend,
    .resume = s3c24xx_serial_resume,
    .resume_noirq = s3c24xx_serial_resume_noirq,
    +#endif
    + SET_RUNTIME_PM_OPS(s3c24xx_serial_runtime_suspend,
    + s3c24xx_serial_runtime_resume, NULL)
    };
    -#define SERIAL_SAMSUNG_PM_OPS (&s3c24xx_serial_pm_ops)
    -
    -#else /* !CONFIG_PM_SLEEP */
    -
    -#define SERIAL_SAMSUNG_PM_OPS NULL
    -#endif /* CONFIG_PM_SLEEP */

    /* Console code */

    @@ -2924,7 +2944,7 @@ static struct platform_driver samsung_serial_driver = {
    .id_table = s3c24xx_serial_driver_ids,
    .driver = {
    .name = "samsung-uart",
    - .pm = SERIAL_SAMSUNG_PM_OPS,
    + .pm = &s3c24xx_serial_pm_ops,
    .of_match_table = of_match_ptr(s3c24xx_uart_dt_match),
    },
    };
    --
    2.33.0
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