linux-kernel - [PATCH] modify mtk uart power and clock management

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Date:   Wed, 17 Jul 2019 20:54:39 +0800
From:   Changqi Hu <changqi.hu@...iatek.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Matthias Brugger <matthias.bgg@...il.com>
CC:     Changqi Hu <changqi.hu@...iatek.com>,
        Peter Shih <pihsun@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        <linux-serial@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <srv_heupstream@...iatek.com>,
        Eddie Huang <eddie.huang@...iatek.com>,
        Yingjoe Chen <yingjoe.chen@...iatek.com>
Subject: [PATCH] modify mtk uart power and clock management

modify mtk uart runtime interface, add uart clock use count.

Signed-off-by: Changqi Hu <changqi.hu@...iatek.com>
---
 drivers/tty/serial/8250/8250_mtk.c | 65 ++++++++++++++++++++++++--------------
 1 file changed, 42 insertions(+), 23 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index f470ded..b0113d1 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -31,6 +31,7 @@
 #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 */
@@ -386,9 +387,18 @@ static void mtk8250_set_flow_ctrl(struct uart_8250_port *up, int mode)
 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;
 }
@@ -398,16 +408,16 @@ 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;
@@ -416,13 +426,23 @@ static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
 static void
 mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
 {
-	if (!state)
-		pm_runtime_get_sync(port->dev);
+	struct uart_8250_port *up = up_to_u8250p(port);
+
+	if (!state) {
+		if (!(up->capabilities & UART_CAP_RPM))
+			mtk8250_runtime_resume(port->dev);
+		else
+			pm_runtime_get_sync(port->dev);
+	}
 
 	serial8250_do_pm(port, state, old);
 
-	if (state)
-		pm_runtime_put_sync_suspend(port->dev);
+	if (state) {
+		if (!(up->capabilities & UART_CAP_RPM))
+			mtk8250_runtime_suspend(port->dev);
+		else
+			pm_runtime_put_sync_suspend(port->dev);
+	}
 }
 
 #ifdef CONFIG_SERIAL_8250_DMA
@@ -499,6 +519,8 @@ 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)
@@ -531,17 +553,12 @@ static int mtk8250_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, data);
 
-	err = mtk8250_runtime_resume(&pdev->dev);
-	if (err)
-		return err;
+	pm_runtime_enable(&pdev->dev);
 
 	data->line = serial8250_register_8250_port(&uart);
 	if (data->line < 0)
 		return data->line;
 
-	pm_runtime_set_active(&pdev->dev);
-	pm_runtime_enable(&pdev->dev);
-
 	return 0;
 }
 
@@ -552,11 +569,13 @@ 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;
 }
 
-- 
1.8.1.1.dirty