serial: 8250-mtk: modify mtk uart power and clock management

MTK uart design no need to control uart clock,
so we just control bus clock in runtime function.
Add uart clock used count to avoid repeatedly switching the clock.

Signed-off-by: Changqi Hu <changqi.hu@mediatek.com>
Link: https://lore.kernel.org/r/1582707225-26815-1-git-send-email-changqi.hu@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index 4d067f515f748bbf8d40a890018485f4b6690033..f839380c2f4c159a1ca617f555d8d45a5c1393e8 100644 (file)
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -32,6 +32,7 @@
 #define MTK_UART_RXTRI_AD      0x14    /* RX Trigger address */
 #define MTK_UART_FRACDIV_L     0x15    /* Fractional divider LSB address */
 #define MTK_UART_FRACDIV_M     0x16    /* Fractional divider MSB address */
+#define MTK_UART_DEBUG0        0x18
 #define MTK_UART_IER_XOFFI     0x20    /* Enable XOFF character interrupt */
 #define MTK_UART_IER_RTSI      0x40    /* Enable RTS Modem status interrupt */
 #define MTK_UART_IER_CTSI      0x80    /* Enable CTS Modem status interrupt */
@@ -388,9 +389,18 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
 static int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
 {
        struct mtk8250_data *data = dev_get_drvdata(dev);
+       struct uart_8250_port *up = serial8250_get_port(data->line);
 
-       clk_disable_unprepare(data->uart_clk);
-       clk_disable_unprepare(data->bus_clk);
+       /* wait until UART in idle status */
+       while
+               (serial_in(up, MTK_UART_DEBUG0));
+
+       if (data->clk_count == 0U) {
+               dev_dbg(dev, "%s clock count is 0\n", __func__);
+       } else {
+               clk_disable_unprepare(data->bus_clk);
+               data->clk_count--;
+       }
 
        return 0;
 }
@@ -400,16 +410,16 @@ static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
        struct mtk8250_data *data = dev_get_drvdata(dev);
        int err;
 
-       err = clk_prepare_enable(data->uart_clk);
-       if (err) {
-               dev_warn(dev, "Can't enable clock\n");
-               return err;
-       }
-
-       err = clk_prepare_enable(data->bus_clk);
-       if (err) {
-               dev_warn(dev, "Can't enable bus clock\n");
-               return err;
+       if (data->clk_count > 0U) {
+               dev_dbg(dev, "%s clock count is %d\n", __func__,
+                       data->clk_count);
+       } else {
+               err = clk_prepare_enable(data->bus_clk);
+               if (err) {
+                       dev_warn(dev, "Can't enable bus clock\n");
+                       return err;
+               }
+               data->clk_count++;
        }
 
        return 0;
@@ -419,12 +429,14 @@ static void
 mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
 {
        if (!state)
-               pm_runtime_get_sync(port->dev);
+               if (!mtk8250_runtime_resume(port->dev))
+                       pm_runtime_get_sync(port->dev);
 
        serial8250_do_pm(port, state, old);
 
        if (state)
-               pm_runtime_put_sync_suspend(port->dev);
+               if (!pm_runtime_put_sync_suspend(port->dev))
+                       mtk8250_runtime_suspend(port->dev);
 }
 
 #ifdef CONFIG_SERIAL_8250_DMA
@@ -501,6 +513,8 @@ static int mtk8250_probe(struct platform_device *pdev)
        if (!data)
                return -ENOMEM;
 
+       data->clk_count = 0;
+
        if (pdev->dev.of_node) {
                err = mtk8250_probe_of(pdev, &uart.port, data);
                if (err)
@@ -533,6 +547,7 @@ static int mtk8250_probe(struct platform_device *pdev)
 
        platform_set_drvdata(pdev, data);
 
+       pm_runtime_enable(&pdev->dev);
        err = mtk8250_runtime_resume(&pdev->dev);
        if (err)
                return err;
@@ -541,9 +556,6 @@ static int mtk8250_probe(struct platform_device *pdev)
        if (data->line < 0)
                return data->line;
 
-       pm_runtime_set_active(&pdev->dev);
-       pm_runtime_enable(&pdev->dev);
-
        data->rx_wakeup_irq = platform_get_irq_optional(pdev, 1);
 
        return 0;
@@ -556,11 +568,13 @@ static int mtk8250_remove(struct platform_device *pdev)
        pm_runtime_get_sync(&pdev->dev);
 
        serial8250_unregister_port(data->line);
-       mtk8250_runtime_suspend(&pdev->dev);
 
        pm_runtime_disable(&pdev->dev);
        pm_runtime_put_noidle(&pdev->dev);
 
+       if (!pm_runtime_status_suspended(&pdev->dev))
+               mtk8250_runtime_suspend(&pdev->dev);
+
        return 0;
 }