dmaengine: stm32-dmamux: add suspend/resume power management support

Add suspend/resume power management relying on PM Runtime engine.
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Link: https://lore.kernel.org/r/20200128094158.20361-2-amelie.delaunay@st.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-dmamux.c

@@ -41,6 +41,9 @@ struct stm32_dmamux_data {
 	u32 dmamux_requests; /* Number of DMA requests routed toward DMAs */
 	spinlock_t lock; /* Protects register access */
 	unsigned long *dma_inuse; /* Used DMA channel */
+	u32 ccr[STM32_DMAMUX_MAX_DMA_REQUESTS]; /* Used to backup CCR register
+						 * in suspend
+						 */
 	u32 dma_reqs[]; /* Number of DMA Request per DMA masters.
 			 *  [0] holds number of DMA Masters.
 			 *  To be kept at very end end of this structure
@@ -318,7 +321,54 @@ static int stm32_dmamux_runtime_resume(struct device *dev)
 }
 #endif
 
+#ifdef CONFIG_PM_SLEEP
+static int stm32_dmamux_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct stm32_dmamux_data *stm32_dmamux = platform_get_drvdata(pdev);
+	int i, ret;
+
+	ret = pm_runtime_get_sync(dev);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < stm32_dmamux->dma_requests; i++)
+		stm32_dmamux->ccr[i] = stm32_dmamux_read(stm32_dmamux->iomem,
+							 STM32_DMAMUX_CCR(i));
+
+	pm_runtime_put_sync(dev);
+
+	pm_runtime_force_suspend(dev);
+
+	return 0;
+}
+
+static int stm32_dmamux_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct stm32_dmamux_data *stm32_dmamux = platform_get_drvdata(pdev);
+	int i, ret;
+
+	ret = pm_runtime_force_resume(dev);
+	if (ret < 0)
+		return ret;
+
+	ret = pm_runtime_get_sync(dev);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < stm32_dmamux->dma_requests; i++)
+		stm32_dmamux_write(stm32_dmamux->iomem, STM32_DMAMUX_CCR(i),
+				   stm32_dmamux->ccr[i]);
+
+	pm_runtime_put_sync(dev);
+
+	return 0;
+}
+#endif
+
 static const struct dev_pm_ops stm32_dmamux_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(stm32_dmamux_suspend, stm32_dmamux_resume)
 	SET_RUNTIME_PM_OPS(stm32_dmamux_runtime_suspend,
 			   stm32_dmamux_runtime_resume, NULL)
 };