spi: omap2-mcspi: add support for pm_runtime autosuspend

Adds support for configuring the omap2-mcspi driver use autosuspend for
runtime power management. This can reduce the latency in starting an
spi transfer by not suspending the device immediately following
completion of a transfer. If another transfer then takes place before
the autosuspend timeout (2 secs), the call to resume the device can
return immediately saving some save/ restore cycles.

Acked-by: Govindraj.R <govindraj.raja@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>

drivers/spi/spi-omap2-mcspi.c

@@ -44,6 +44,7 @@
 #include <plat/mcspi.h>
 
 #define OMAP2_MCSPI_MAX_FREQ		48000000
+#define SPI_AUTOSUSPEND_TIMEOUT		2000
 
 #define OMAP2_MCSPI_REVISION		0x00
 #define OMAP2_MCSPI_SYSSTATUS		0x14
@@ -265,7 +266,8 @@ static void omap2_mcspi_restore_ctx(struct omap2_mcspi *mcspi)
 }
 static void omap2_mcspi_disable_clocks(struct omap2_mcspi *mcspi)
 {
-	pm_runtime_put_sync(mcspi->dev);
+	pm_runtime_mark_last_busy(mcspi->dev);
+	pm_runtime_put_autosuspend(mcspi->dev);
 }
 
 static int omap2_mcspi_enable_clocks(struct omap2_mcspi *mcspi)
@@ -1212,6 +1214,8 @@ static int __devinit omap2_mcspi_probe(struct platform_device *pdev)
 	if (status < 0)
 		goto dma_chnl_free;
 
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_autosuspend_delay(&pdev->dev, SPI_AUTOSUSPEND_TIMEOUT);
 	pm_runtime_enable(&pdev->dev);
 
 	if (status || omap2_mcspi_master_setup(mcspi) < 0)