[PATCH 1/2] dmaengine: qcom: bam_dma: Take a PM ref at remove()

[Mostafa Saleh <smostafa@google.com>]

bam_dma_remove() calls pm_runtime_dont_use_autosuspend() and
pm_runtime_force_suspend(), which on a BAM with its own clock disables
bam_clk, and only then writes BAM_IRQ_SRCS_MSK_EE and terminates the
channels, touching registers of a block whose clock has just been
removed, causing the board to reset.

Sashiko(Locally) also reports, it then calls clk_disable_unprepare()
on a clock that runtime suspend already disabled, which can trigger
"already disabled" warning in clk_core_disable().

Hold a runtime PM reference across the register accesses and the
channel teardown. Once the hardware is quiet, disable runtime PM with
the device still active and drop the clock exactly once, balancing the
clk_prepare_enable() in probe.

Fixes: 7d2545599f5b ("dmaengine: qcom-bam-dma: Add pm_runtime support")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 drivers/dma/qcom/bam_dma.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index f67a93a37d48..bd583f78e0c1 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -1403,12 +1403,10 @@ static void bam_dma_remove(struct platform_device *pdev)
 	struct bam_device *bdev = platform_get_drvdata(pdev);
 	u32 i;
 
-	pm_runtime_dont_use_autosuspend(&pdev->dev);
-	pm_runtime_force_suspend(&pdev->dev);
-
 	of_dma_controller_free(pdev->dev.of_node);
 	dma_async_device_unregister(&bdev->common);
 
+	pm_runtime_get_sync(&pdev->dev);
 	/* mask all interrupts for this execution environment */
 	writel_relaxed(0, bam_addr(bdev, 0,  BAM_IRQ_SRCS_MSK_EE));
 
@@ -1428,6 +1426,9 @@ static void bam_dma_remove(struct platform_device *pdev)
 
 	tasklet_kill(&bdev->task);
 
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
 	clk_disable_unprepare(bdev->bamclk);
 }
 
-- 
2.56.0.212.g129ede20d9-goog