[PATCH v4 1/6] dmaengine: zynqmp_dma: Use PM guard for probe-time runtime PM reference

[Golla Nagendra]

Replace pm_runtime_resume_and_get() with the PM_RUNTIME_ACQUIRE_AUTOSUSPEND
guard to manage the probe-time runtime PM reference lifecycle. If the guard
acquire fails, fail probe immediately so a broken device is never
registered.

When runtime PM is not enabled for the device, call
zynqmp_dma_runtime_resume() directly after pm_runtime_enable() to bring the
clocks up for probe.

On probe failure after a successful guard acquire, drop the reference with
zynqmp_dma_probe_pm_put(), inhibit the guard destructor with
retain_and_null_ptr(), and gate the clocks through
zynqmp_dma_probe_fail(). When runtime PM is enabled,
zynqmp_dma_probe_pm_put() uses pm_runtime_put_sync_suspend(). When runtime
PM is not enabled for the device, balance the guard usage counter with
pm_runtime_put_noidle() and gate the clocks with
zynqmp_dma_runtime_suspend(). Runtime PM does not suspend a device that
is already disabled, so pair every direct zynqmp_dma_runtime_suspend()
call with pm_runtime_set_suspended() to keep the runtime PM status in
sync with the clocks.

On probe success, release the probe-time reference with
pm_runtime_put_sync_autosuspend() when runtime PM is enabled for the
device. When runtime PM is not enabled for the device, balance the guard
usage counter with pm_runtime_put_noidle() only and leave the clocks
enabled so that later channel allocation can use the hardware. Inhibit the
guard destructor with retain_and_null_ptr(pm).

Signed-off-by: Golla Nagendra <nagendra.golla@xxxxxxx>
---
 drivers/dma/xilinx/zynqmp_dma.c | 68 ++++++++++++++++++++++++++++++-----------
 1 file changed, 50 insertions(+), 18 deletions(-)

diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index 3b7dfa53f972..a48106e404e7 100644
--- a/drivers/dma/xilinx/zynqmp_dma.c
+++ b/drivers/dma/xilinx/zynqmp_dma.c
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/clk.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/cleanup.h>
 #include <linux/pm_runtime.h>
 
 #include "../dmaengine.h"
@@ -1077,6 +1078,29 @@ static const struct dev_pm_ops zynqmp_dma_dev_pm_ops = {
 			   zynqmp_dma_runtime_resume, NULL)
 };
 
+static void zynqmp_dma_probe_pm_put(struct device *dev)
+{
+	if (pm_runtime_enabled(dev))
+		pm_runtime_put_sync_suspend(dev);
+	else
+		pm_runtime_put_noidle(dev);
+}
+
+static int zynqmp_dma_probe_fail(struct zynqmp_dma_device *zdev, int ret)
+{
+	bool rpm_disabled = !pm_runtime_enabled(zdev->dev);
+
+	zynqmp_dma_chan_remove(zdev->chan);
+	zynqmp_dma_probe_pm_put(zdev->dev);
+	pm_runtime_disable(zdev->dev);
+	if (rpm_disabled || !pm_runtime_status_suspended(zdev->dev)) {
+		zynqmp_dma_runtime_suspend(zdev->dev);
+		pm_runtime_set_suspended(zdev->dev);
+	}
+
+	return ret;
+}
+
 /**
  * zynqmp_dma_probe - Driver probe function
  * @pdev: Pointer to the platform_device structure
@@ -1087,7 +1111,7 @@ static int zynqmp_dma_probe(struct platform_device *pdev)
 {
 	struct zynqmp_dma_device *zdev;
 	struct dma_device *p;
-	int ret;
+	int ret, pm_err;
 
 	zdev = devm_kzalloc(&pdev->dev, sizeof(*zdev), GFP_KERNEL);
 	if (!zdev)
@@ -1128,21 +1152,30 @@ static int zynqmp_dma_probe(struct platform_device *pdev)
 	pm_runtime_set_autosuspend_delay(zdev->dev, ZDMA_PM_TIMEOUT);
 	pm_runtime_use_autosuspend(zdev->dev);
 	pm_runtime_enable(zdev->dev);
-	ret = pm_runtime_resume_and_get(zdev->dev);
-	if (ret < 0) {
-		dev_err(&pdev->dev, "device wakeup failed.\n");
-		pm_runtime_disable(zdev->dev);
-	}
 	if (!pm_runtime_enabled(zdev->dev)) {
 		ret = zynqmp_dma_runtime_resume(zdev->dev);
-		if (ret)
+		if (ret) {
+			pm_runtime_disable(zdev->dev);
 			return ret;
+		}
+	}
+	PM_RUNTIME_ACQUIRE_AUTOSUSPEND(zdev->dev, pm);
+	pm_err = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (pm_err) {
+		retain_and_null_ptr(pm);
+		pm_runtime_disable(zdev->dev);
+		if (!pm_runtime_status_suspended(zdev->dev)) {
+			zynqmp_dma_runtime_suspend(zdev->dev);
+			pm_runtime_set_suspended(zdev->dev);
+		}
+		return dev_err_probe(&pdev->dev, pm_err, "device wakeup failed\n");
 	}
 
 	ret = zynqmp_dma_chan_probe(zdev, pdev);
 	if (ret) {
 		dev_err_probe(&pdev->dev, ret, "Probing channel failed\n");
-		goto free_chan_resources;
+		retain_and_null_ptr(pm);
+		return zynqmp_dma_probe_fail(zdev, ret);
 	}
 
 	p->dst_addr_widths = BIT(zdev->chan->bus_width / 8);
@@ -1151,7 +1184,8 @@ static int zynqmp_dma_probe(struct platform_device *pdev)
 	ret = dma_async_device_register(&zdev->common);
 	if (ret) {
 		dev_err(zdev->dev, "failed to register the dma device\n");
-		goto free_chan_resources;
+		retain_and_null_ptr(pm);
+		return zynqmp_dma_probe_fail(zdev, ret);
 	}
 
 	ret = of_dma_controller_register(pdev->dev.of_node,
@@ -1159,19 +1193,17 @@ static int zynqmp_dma_probe(struct platform_device *pdev)
 	if (ret) {
 		dev_err_probe(&pdev->dev, ret, "Unable to register DMA to DT\n");
 		dma_async_device_unregister(&zdev->common);
-		goto free_chan_resources;
+		retain_and_null_ptr(pm);
+		return zynqmp_dma_probe_fail(zdev, ret);
 	}
 
-	pm_runtime_put_sync_autosuspend(zdev->dev);
+	if (pm_runtime_enabled(zdev->dev))
+		pm_runtime_put_sync_autosuspend(zdev->dev);
+	else
+		pm_runtime_put_noidle(zdev->dev);
+	retain_and_null_ptr(pm);
 
 	return 0;
-
-free_chan_resources:
-	zynqmp_dma_chan_remove(zdev->chan);
-	if (!pm_runtime_enabled(zdev->dev))
-		zynqmp_dma_runtime_suspend(zdev->dev);
-	pm_runtime_disable(zdev->dev);
-	return ret;
 }
 
 /**

-- 
2.43.7