[PATCH v2 2/2] dmaengine: dw-axi-dmac: fix PM for system sleep and channel alloc

[tze . yee . ng]

From: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>

The driver only had runtime PM callbacks. If a channel stayed allocated
across system suspend/resume, the runtime usage count could remain
non-zero while hardware state (DMAC_CFG, clocks) was lost, and
axi_dma_runtime_resume() would not run to restore it.

Add system-sleep PM ops that use pm_runtime_force_suspend() and
pm_runtime_force_resume() so suspend/resume reuses the existing
axi_dma_suspend() and axi_dma_resume() paths.

Replace pm_runtime_get() with pm_runtime_resume_and_get() in
dma_chan_alloc_chan_resources() so clocks are enabled before a client
can immediately submit a transfer and touch MMIO.

Signed-off-by: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>
---
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
index f7a50f470461..bcefaff03b5c 100644
--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
@@ -516,11 +516,17 @@ static void dw_axi_dma_synchronize(struct dma_chan *dchan)
 static int dma_chan_alloc_chan_resources(struct dma_chan *dchan)
 {
 	struct axi_dma_chan *chan = dchan_to_axi_dma_chan(dchan);
+	int ret;
+
+	ret = pm_runtime_resume_and_get(chan->chip->dev);
+	if (ret < 0)
+		return ret;
 
 	/* ASSERT: channel is idle */
 	if (axi_chan_is_hw_enable(chan)) {
 		dev_err(chan2dev(chan), "%s is non-idle!\n",
 			axi_chan_name(chan));
+		pm_runtime_put(chan->chip->dev);
 		return -EBUSY;
 	}
 
@@ -531,12 +537,11 @@ static int dma_chan_alloc_chan_resources(struct dma_chan *dchan)
 					  64, 0);
 	if (!chan->desc_pool) {
 		dev_err(chan2dev(chan), "No memory for descriptors\n");
+		pm_runtime_put(chan->chip->dev);
 		return -ENOMEM;
 	}
 	dev_vdbg(dchan2dev(dchan), "%s: allocating\n", axi_chan_name(chan));
 
-	pm_runtime_get(chan->chip->dev);
-
 	return 0;
 }
 
@@ -1663,6 +1668,8 @@ static void dw_remove(struct platform_device *pdev)
 }
 
 static const struct dev_pm_ops dw_axi_dma_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
 	SET_RUNTIME_PM_OPS(axi_dma_runtime_suspend, axi_dma_runtime_resume, NULL)
 };
 
-- 
2.43.7