dmaengine: rcar-dmac: Make DMAC reinit during system resume explicit

[Geert Uytterhoeven <geert+renesas@glider.be>]

The current (empty) system sleep callbacks rely on the PM core to force
a runtime resume to reinitialize the DMAC registers during system
resume.  Without a reinitialization, e.g. SCIF DMA will hang silently
after a system resume on R-Car Gen3.

Make this explicit by using pm_runtime_force_{suspend,resume}() as the
system sleep callbacks instead.  Use SET_LATE_SYSTEM_SLEEP_PM_OPS() as
DMA engines must be initialized before all DMA slave devices.

Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is a dependency for "[PATCH 1/2] PM / genpd: Stop/start devices
without pm_runtime_force_suspend/resume()"
(https://www.spinics.net/lists/kernel/msg2696802.html), so perhaps it
makes most sense if Rafael takes it through the PM tree?

Thanks!
---
 drivers/dma/sh/rcar-dmac.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index fb06b193ad252086..06e4e604eebb79f6 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1657,22 +1657,6 @@ static struct dma_chan *rcar_dmac_of_xlate(struct of_phandle_args *dma_spec,
  * Power management
  */
 
-#ifdef CONFIG_PM_SLEEP
-static int rcar_dmac_sleep_suspend(struct device *dev)
-{
-	/*
-	 * TODO: Wait for the current transfer to complete and stop the device.
-	 */
-	return 0;
-}
-
-static int rcar_dmac_sleep_resume(struct device *dev)
-{
-	/* TODO: Resume transfers, if any. */
-	return 0;
-}
-#endif
-
 #ifdef CONFIG_PM
 static int rcar_dmac_runtime_suspend(struct device *dev)
 {
@@ -1688,7 +1672,13 @@ static int rcar_dmac_runtime_resume(struct device *dev)
 #endif
 
 static const struct dev_pm_ops rcar_dmac_pm = {
-	SET_SYSTEM_SLEEP_PM_OPS(rcar_dmac_sleep_suspend, rcar_dmac_sleep_resume)
+	/*
+	 * TODO for system sleep/resume:
+	 *   - Wait for the current transfer to complete and stop the device,
+	 *   - Resume transfers, if any.
+	 */
+	SET_LATE_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				     pm_runtime_force_resume)
 	SET_RUNTIME_PM_OPS(rcar_dmac_runtime_suspend, rcar_dmac_runtime_resume,
 			   NULL)
 };