ARM: OMAP2+: UART: Get context loss count to context restore

Avoid unconditional context restore every time we gate uart
clocks. Check whether context loss happened based on which
we can context restore uart regs from uart_port structure.

Signed-off-by: Govindraj.R <govindraj.raja@ti.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de> (for drivers/tty changes)
Signed-off-by: Kevin Hilman <khilman@ti.com>

arch/arm/mach-omap2/serial.c

@@ -33,6 +33,7 @@
 #include <plat/dma.h>
 #include <plat/omap_hwmod.h>
 #include <plat/omap_device.h>
+#include <plat/omap-pm.h>
 
 #include "prm2xxx_3xxx.h"
 #include "pm.h"
@@ -478,6 +479,7 @@ void __init omap_serial_init_port(struct omap_board_data *bdata)
 	omap_up.dma_enabled = uart->dma_enabled;
 	omap_up.uartclk = OMAP24XX_BASE_BAUD * 16;
 	omap_up.flags = UPF_BOOT_AUTOCONF;
+	omap_up.get_context_loss_count = omap_pm_get_dev_context_loss_count;
 
 	pdata = &omap_up;
 	pdata_size = sizeof(struct omap_uart_port_info);

arch/arm/plat-omap/include/plat/omap-serial.h

@@ -62,6 +62,8 @@ struct omap_uart_port_info {
 	bool			dma_enabled;	/* To specify DMA Mode */
 	unsigned int		uartclk;	/* UART clock rate */
 	upf_t			flags;		/* UPF_* flags */
+
+	int (*get_context_loss_count)(struct device *);
 };
 
 struct uart_omap_dma {
@@ -114,6 +116,7 @@ struct uart_omap_port {
 	unsigned char		msr_saved_flags;
 	char			name[20];
 	unsigned long		port_activity;
+	u32			context_loss_cnt;
 };
 
 #endif /* __OMAP_SERIAL_H__ */

drivers/tty/serial/omap-serial.c

@@ -1440,15 +1440,31 @@ static void serial_omap_restore_context(struct uart_omap_port *up)
 #ifdef CONFIG_PM_RUNTIME
 static int serial_omap_runtime_suspend(struct device *dev)
 {
+	struct uart_omap_port *up = dev_get_drvdata(dev);
+	struct omap_uart_port_info *pdata = dev->platform_data;
+
+	if (!up)
+		return -EINVAL;
+
+	if (pdata->get_context_loss_count)
+		up->context_loss_cnt = pdata->get_context_loss_count(dev);
+
 	return 0;
 }
 
 static int serial_omap_runtime_resume(struct device *dev)
 {
 	struct uart_omap_port *up = dev_get_drvdata(dev);
+	struct omap_uart_port_info *pdata = dev->platform_data;
 
-	if (up)
-		serial_omap_restore_context(up);
+	if (up) {
+		if (pdata->get_context_loss_count) {
+			u32 loss_cnt = pdata->get_context_loss_count(dev);
+
+			if (up->context_loss_cnt != loss_cnt)
+				serial_omap_restore_context(up);
+		}
+	}
 
 	return 0;
 }