linux-kernel - [PATCH 5/8] serial: imx: save and restore context in the suspend path

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Date:	Sun,  9 Aug 2015 11:19:06 -0700
From:	Eduardo Valentin <edubezval@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, Fabio Stevam <festevam@...il.com>
Cc:	Linux PM <linux-pm@...r.kernel.org>,
	Eduardo Valentin <edubezval@...il.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/8] serial: imx: save and restore context in the suspend path

This change teaches the imx serial driver to save its
context and restore it across suspend and resume path.
To do so, it introduces serial_imx_restore_context()
and serial_imx_save_context() functions. They use
a shadow set of registers to save key registers
and restore them accordingly. These functions can
be reused on other situations, when the device
context is lost.

Cc: Fabio Stevam <festevam@...il.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jslaby@...e.com>
Cc: linux-serial@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@...il.com>
---
 drivers/tty/serial/imx.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index a03855d..494b182 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -217,6 +217,8 @@ struct imx_port {
 	unsigned int		tx_bytes;
 	unsigned int		dma_tx_nents;
 	wait_queue_head_t	dma_wait;
+	unsigned int		saved_reg[8];
+	bool			context_saved;
 };
 
 struct imx_port_ucrs {
@@ -1803,6 +1805,36 @@ static struct uart_driver imx_reg = {
 	.cons           = IMX_CONSOLE,
 };
 
+static void serial_imx_restore_context(struct imx_port *sport)
+{
+	if (!sport->context_saved)
+		return;
+
+	writel(sport->saved_reg[4], sport->port.membase + UFCR);
+	writel(sport->saved_reg[5], sport->port.membase + UBIR);
+	writel(sport->saved_reg[6], sport->port.membase + UBMR);
+	writel(sport->saved_reg[7], 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);
+	sport->context_saved = false;
+}
+
+static void serial_imx_save_context(struct imx_port *sport)
+{
+	/* Save necessary regs */
+	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 + UBIR);
+	sport->saved_reg[6] = readl(sport->port.membase + UBMR);
+	sport->saved_reg[7] = readl(sport->port.membase + IMX21_UTS);
+	sport->context_saved = true;
+}
+
 static void serial_imx_enable_wakeup(struct imx_port *sport, bool on)
 {
 	unsigned int val;
@@ -1826,6 +1858,7 @@ static int serial_imx_suspend(struct device *dev)
 {
 	struct imx_port *sport = dev_get_drvdata(dev);
 
+	serial_imx_save_context(sport);
 	/* enable wakeup from i.MX UART */
 	serial_imx_enable_wakeup(sport, true);
 
@@ -1841,6 +1874,7 @@ static int serial_imx_resume(struct device *dev)
 	/* disable wakeup from i.MX UART */
 	serial_imx_enable_wakeup(sport, false);
 
+	serial_imx_restore_context(sport);
 	uart_resume_port(&imx_reg, &sport->port);
 
 	return 0;
-- 
2.5.0

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