-----Original Message-----
From: linux-arm-kernel [mailto:linux-arm-kernel-bounces at lists.infradead.org] On
Behalf Of Shenwei Wang
Sent: 2015?7?17? 15:30
To: gregkh at linuxfoundation.org
Cc: linux-arm-kernel at lists.infradead.org; linux-serial at vger.kernel.org
Subject: [PATCH 1/1] Serial: imx: add dev_pm_ops to support suspend to ram/disk

When system goes into low power states like SUSPEND_MEM and HIBERNATION,
the hardware IP block may be powered off to reduce the power consumption.
This power down may cause problems on some imx platforms, because the
hardware settings are reset to its power on default values which may differ from
the ones when it power off. This patch added the dev_pm_ops and implemented
two callbacks: suspend_noirq and resume_noirq, which will save the necessory
hardware parameters right before power down and recover them before system
uses the hardware.

Signed-off-by: Shenwei Wang <redacted>
---
 drivers/tty/serial/imx.c | 54
++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index

c8cfa06..acaaa68 100644

--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c

@@ -216,6 +216,7 @@ struct imx_port {
 	unsigned int		tx_bytes;
 	unsigned int		dma_tx_nents;
 	wait_queue_head_t	dma_wait;
+	unsigned int            saved_reg[10];
 };

 struct imx_port_ucrs {

@@ -1986,6 +1987,58 @@ static int serial_imx_remove(struct platform_device

*pdev)
 	return uart_remove_one_port(&imx_reg, &sport->port);  }

+static int imx_serial_port_suspend_noirq(struct device *dev) {
+	struct platform_device *pdev = to_platform_device(dev);
+	struct imx_port *sport = platform_get_drvdata(pdev);
+
+	/* Save necessary regs */
+	clk_enable(sport->clk_ipg);
+	sport->saved_reg[0] = readl(sport->port.membase + UCR1);
+	sport->saved_reg[1] = readl(sport->port.membase + UCR2);
+	sport->saved_reg[2] = readl(sport->port.membase + UCR3);
+	sport->saved_reg[3] = readl(sport->port.membase + UCR4);
+	sport->saved_reg[4] = readl(sport->port.membase + UFCR);
+	sport->saved_reg[5] = readl(sport->port.membase + UESC);
+	sport->saved_reg[6] = readl(sport->port.membase + UTIM);
+	sport->saved_reg[7] = readl(sport->port.membase + UBIR);
+	sport->saved_reg[8] = readl(sport->port.membase + UBMR);
+	sport->saved_reg[9] = readl(sport->port.membase + IMX21_UTS);
+	clk_disable(sport->clk_ipg);
+
+	pr_debug("0x%p (%d)\r\n", sport->port.membase, sport->port.line);
+
+	return 0;
+}
+
+static int imx_serial_port_resume_noirq(struct device *dev) {
+	struct platform_device *pdev = to_platform_device(dev);
+	struct imx_port *sport = platform_get_drvdata(pdev);
+
+	clk_enable(sport->clk_ipg);
+	writel(sport->saved_reg[4], sport->port.membase + UFCR);
+	writel(sport->saved_reg[5], sport->port.membase + UESC);
+	writel(sport->saved_reg[6], sport->port.membase + UTIM);
+	writel(sport->saved_reg[7], sport->port.membase + UBIR);
+	writel(sport->saved_reg[8], sport->port.membase + UBMR);
+	writel(sport->saved_reg[9], sport->port.membase + IMX21_UTS);
+	writel(sport->saved_reg[0], sport->port.membase + UCR1);
+	writel(sport->saved_reg[1] | 0x1, sport->port.membase + UCR2);
+	writel(sport->saved_reg[2], sport->port.membase + UCR3);
+	writel(sport->saved_reg[3], sport->port.membase + UCR4);
+	clk_disable(sport->clk_ipg);
+
+	pr_debug("0x%p (%d)\r\n", sport->port.membase, sport->port.line);
+
+	return 0;
+}
+
+static const struct dev_pm_ops imx_serial_port_pm_ops = {
+	.suspend_noirq = imx_serial_port_suspend_noirq,
+	.resume_noirq = imx_serial_port_resume_noirq, };
+
 static struct platform_driver serial_imx_driver = {
 	.probe		= serial_imx_probe,
 	.remove		= serial_imx_remove,

@@ -1996,6 +2049,7 @@ static struct platform_driver serial_imx_driver = {
 	.driver		= {
 		.name	= "imx-uart",
 		.of_match_table = imx_uart_dt_ids,
+		.pm	= &imx_serial_port_pm_ops,
 	},
 };

--

2.5.0.rc2



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