dma: shdma: transfer based runtime PM

Currently the shdma dmaengine driver uses runtime PM to save power, when
no channel on the specific controller is requested by a user. This patch
switches the driver to count individual DMA transfers. That way the
controller can be powered down between transfers, even if some of its
channels are in use.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/shdma.h

@@ -23,6 +23,12 @@
 
 struct device;
 
+enum dmae_pm_state {
+	DMAE_PM_ESTABLISHED,
+	DMAE_PM_BUSY,
+	DMAE_PM_PENDING,
+};
+
 struct sh_dmae_chan {
 	dma_cookie_t completed_cookie;	/* The maximum cookie completed */
 	spinlock_t desc_lock;		/* Descriptor operation lock */
@@ -38,6 +44,7 @@ struct sh_dmae_chan {
 	u32 __iomem *base;
 	char dev_id[16];		/* unique name per DMAC of channel */
 	int pm_error;
+	enum dmae_pm_state pm_state;
 };
 
 struct sh_dmae_device {